Fabrication of Biologically Active Fish Bone Derived Hydroxyapatite and Montmorillonite Blended Sodium Alginate Composite for In-Vitro Drug Delivery Studies

Fishbone comprising hydroxyapatite (bio-ceramic) is regularly viewed as a natural resource for biological and pharmaceutical applications. In this study, hydroxyapatite has been prepared from fishbone waste using thermal calcination method. The composite hydroxyapatite–montmorillonite–sodium alginate was synthesized by co-precipitation method. Various functional groups of biocomposite were characterised using Fourier transform infrared spectroscopy. Thermal stability and crystallinity of biocomposite were analysed through thermal gravimetric analysis and X-ray diffraction studies respectively. The morphological surface of composites was studied using scanning electron microscopy. The synthesized composite was designed to study the enhanced biological potential such as antibacterial, antioxidant, antidiabetic, drug loading and the drug releasing ability. Antioxidant and anti-diabetic analysis of composite were studied using phosphomolybdenum and α-amylase inhibitory method respectively. The drug releasing ability of compounds (Doxorubicin and Curcumin) were investigated by UV–spectrophotometry method at different pH medium (pH = 5.5, 6.8 and 7.4). Additionally, in-vitro kinetic studies were carried out on composite to determine the drug releasing ability of doxorubicin and curcumin.


Introduction
Osteosarcoma bone tumour can metastasize to infiltrate the bones, resulting in bone defects and posing a critical threat to human health [1]. Surgical treatment, chemotherapy, and radiotherapy are currently the most effective treatments for bone tumours. In chemotherapy, patients ensuing excessive intake of drugs leads to nausea, diarrhoea, hair loss, vomiting and killing of healthy cells in the human body [2]. Due to the repercussions of chemotherapy, limiting the dosage of the drug resulted in diminishing anti-cancer efficacy. Drug carriers are used to control the drug delivery, to provide the effective chemotherapy for the patients as well as minimal side effects in the treatment [3].
Chemotherapy drugs doxorubicin (DOX) and Curcumin (Cur) are commonly used in the treatment of osteosarcoma to inhibit the growth of tumour cells [4]. Though, excessive release of drug makes significant changes in the cytotoxicity results. Certainly, the cell death results contradiction with the count of normal cell death [5]. In order to attain the longterm potent release and permit sustained release of drugs, suitable carrier materials are needed that are of appropriate biocompatibility [6]. Recent researches have been focus on design, preparation and improvement of drug carriers.
Hydroxyapatite (HA) has received increasing attention as a potential material for drug delivery carriers because of its nontoxicity, biocompatibility, and charge groups. This aspect of composite is suitable for loading the drugs onto material [7,8]. Hydroxyapatite promotes osteogenesis process during drug delivery. It has been noticed an appropriate candidate for the prevention of tumour recurrence after osteosarcoma resection and nurture bone regeneration [9].

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The raw materials for producing hydroxyapatite can also be obtained from natural calcium sources like mussel shells and eggshells [10,11]. In addition to the above, fishbone is considered as the inexpensive and easily accessible source of Hydroxyapatite. It is regarded as non-essential waste material obtained from by-product of seafood industry [12]. A large amount of fishbone waste is generated each year due to increase in fish consumption around the world. Globally, approximately 970-2700 billion tons of fish have been catching with 450-1000 billion being consumed by humans [13]. Presence of some terminal groups like -OH in the HA can be layered like structures offers the possibility of immobilizing biological recognition exhibiting proteins in an oriented way, ability can be well exploited for oriented immobilization of enzymes and antibodies [14]. Naturally derived hydroxyapatite provides magnesium, zinc and strontium ions. Moreover, natural hydroxyapatite contains considerable amounts of carbonates and trace elements, thereby stimulating the biological activity of osteoblasts in the body [15,16]. Because of being too brittle due to ceramic nature, also developing biomaterial surfaces to attain drug delivery properties by increasing percentage of drug holding and avoiding burst release [17].
Sodium Alginate (SA) is a class of biopolymer, derive from marine algae, brown seaweeds and soil bacteria, it is called linear polysaccharide [18]. Properties of composites such as thickening, gelling and film forming ability makes better efficacies in many industrial fields including pharmaceutical, medical, paper, leather, food, immobilized catalysts and textile printing [19,20]. Biocompatibility, biodegradability, less toxicity and hydrophilicity of the alginate are highly suitable for drug delivery applications. Hydroxyapatite along with alginate increases the cell attachment in the inner parts and offers a suitable choice of composite for bone tissue engineering [21]. Usually polysaccharides producing composite possess high water content and release of low molecular weight drugs due to the high rate of burst release and it is not effectively controlled. Thus compared to protein drugs, controlled release of low molecular weight anticancer drugs through encapsulation in polysaccharides such as alginate has certain limitations [22]. Since, many researches have been progressing to perform using clays, specific task such as delayed or target drug release, improve drug dissolution, increase drug stability, and modify drug delivery patterns. Among clays, Montmorillonite (MMT) has drawn considerable attention because of its high specific surface area, swelling capacity and cationic exchange capacity makes modification of polymer. This tends to expand the applications in various fields such as adsorption and sensor etc., [23,24]. Also, controlled release properties, oral bioavailability, gastrointestinal cross-ability and muco-adhesiveness make it suitable for pharmaceutical applications [25].
The ultimate aim of this work is to prepare a bio-composite derived from natural hydroxyapatite and evaluate a new drug delivery material and carry out in-vitro efficacy of the prepared bio-composite material in biological applications including antimicrobial, antioxidant and antidiabetic. The synthesis route is new that the preparation of hydroxyapatite from Seer fish bone bio-waste. To the best of our knowledge, there are no considerable works that have been done on hydroxyapatite / montmorillonite/sodium alginate composite is a novel biocomposite moreover, so far no drug release / drug encapsulation studies was carried out for this composite.

Preparation of Hydroxyapatite (HA)
Fishbone (1 kg) was boiled in water at 150 °C for about 30 min until the flesh and skin were eliminated from the bone. Then, it is allowed to react with 10% butanol for 48 h and then it is treated with strongly alkaline medium and followed by acetone to remove the fat, proteins, lipids, oils and other organic contents. Furthermore, the product was washed with distilled water and filtered through a suction pump until the pH was neutral. The obtained fish bone was dried in a hot air oven for 5 h at 80 °C. The product was crushed and ground into powder using ball milling before calcination process. 2 g of fishbone powder and phosphate buffer mixture was placed in silica crucible and subjected to a temperature of 900 °C for 6 h in an electrical muffle furnace at a ramp rate of 15 °C/min and then allowed to cool to room temperature. Resulting white material HA was obtained and pulverized into fine powder.

Synthesis of Hydroxyapatite/Montmorillonite (HA/MMT) Composite
A required amount of montmorillonite clay was ground and dried to 120 °C for 24 h and stored in desiccators prior to use. In 100 mL of deionized water, 0.5 g of montmorillonite clay was dispersed and sonicated using an ultrasonicator at 80 watts for 30 min. Then, the 1 g of as-prepared hydroxyapatite was added slowly in 100 mL of montmorillonite suspension, agitated under magnetic stirrer for 2 h, followed by sonication for 30 min. The obtained suspension was centrifuged and slurry was separated by discarding the supernatant. Afterwards, it was washed twice with distilled water and then ethanol removed the impurities and unreacted substance. Furthermore, it was allowed to dry in a vacuum oven at 60 °C for 5 h and the resulting HA/MMT composite was ground well into powder.

Synthesis of Hydroxyapatite/Sodium Alginate (HA/SA) Composite
Sodium alginate (0.5 g) was dissolved in distilled water (100 ml) at 60 °C and obtained viscous solution was allowed to cool to room temperature. Then, 1 g of as prepared hydroxyapatite was added slowly to viscous alginate solution under constant stirring using magnetic stirrer at 1000 rpm for 1 h. The obtained suspension, the slurry was separated by discarding the supernatant. Afterwards, composite was washed with distilled water, and then ethanol was added to remove the impurities. After removal of impurities, the HA / SA composite was dried in a vacuum oven at 60 °C for 5 h and grounded well into powder (Scheme 1).

Synthesis of Hydroxyapatite/Montmorillonite/ Sodium Alginate Composite (HA/MMT/SA)
0.5 g of Sodium alginate was dissolved in distilled water (100 ml) at 60 °C and was cooled to room temperature (25 °C). After, 1 g of as prepared HA/MMT was dispersed stirred and followed by the sonication for 15 min. Then, prepared viscous alginate solution was added gradually into resulting HA/MMT clay suspension was continuously stirred under magnetic stirrer at 1000 rpm for 1 h. The slurry was separated from the suspension by centrifugation and washed with distilled water and ethanol to make free from impurity substances. The resulting HA/MMT/SA composite was then dried in a vacuum oven at 60 °C for 5 h and ground finely into powder (Scheme.1).

Fourier Transform Infra-Red (FT-IR) Analysis
Infra-red spectra of prepared composites were studied using Fourier Transform Infra-red analysis. The compounds were characterised at the range of 400-4000 cm −1 using the Perkin Elmer Spectrum Version 10.4.00, KBr pellet method.

Porosity
The percentage of spaces or air voids (pores) within a solid material in the dry state of the polymer composite represents the percentage of porosity (ϕ), which is estimating from their densities. The weights of polymer and their derivatives were measured using the formula given below.
where Vb and Vma are the total volume of the compound and the volume of matrix respectively.

X-Ray Diffraction (XRD) Studies
Wide-angle X-ray diffractogram and Small X-ray diffractogram were recorded for prepared samples using 2.2KW Cu-anode ceramic tube, Lynx Eye Detector (Silicon strip detector technology) and Scintillation Detector (for low angle XRD analysis) D8 advance, Bruker, Germany. The XRD spectra were analysed with an applied voltage of 40 kV with a current of 30 mA, Cu Kα radiation (λ = 0.15406 nm), scan rate of 0.02˚ per second and the angles from 0˚ to 10˚ (small angle) and 10° to 90° (wide angle) were analysed for the samples. The crystalline size was calculated by using following equation where D is the crystallite size, λ is the wavelength of X-rays, k is the Scherrer constant and β is the full width at half maximum FWHM (radian).

Thermal Gravimetric-Differential Thermal (TGA-DTA) Analysis
TGA-DTA curves of compounds were analysed with 2.2 mg of sample in the alumina pan and the heating rate of 20 °C/min with the flow of nitrogen gas 100 mL /min. The TGA-DTA curves were recorded for prepared composites using SDT Q600, TA Instruments, USA.

Field Emission Scanning Electron Microscope (FESEM) Analysis
The surface morphologies of hydroxyapatite and the composites were recorded using ZEISS SIGMA Field Emission Scanning Electron Microscope. The bioceramic composites were coated with gold and palladium using QUORUM Sputter Coater sc7620 before analysis.

Energy Dispersive Spectroscopic (EDAX) Analysis
The EDAX spectra were analyzed for the percentage ratios of metal ions, carbon, nitrogen, oxygen, and other elements Scheme 1 Design and synthesis of hydroxyapatite/montmorillonite blended biopolymer composite present in the synthesized hydroxyapatite-montmorillonite-biopolymer composite. The spectra were recorded using the instrument of Thermo Fisher Scientific FEI Company of USA.

Antibacterial Activity (Agar Plate Method)
The antibacterial activities were studied by the agar plate method for prepared biocomposite derivatives. About  Ampicillin was used as reference drug in this study [28].

Total Antioxidant Studies (Phosphomolybdenum Method)
Wound and damaged cells are repaired by the antioxidant materials. Hence, antioxidants play important role in human cell proliferation and development. The total antioxidant studies were carried out through the phosphomolybdenum method [29]. 0.3 mL of test samples and Vitamin-C with various concentrations such as 10 μg/mL, 50 μg/mL, 100 μg/ mL, 250 μg/mL and 500 μg/mL were blended with 3 mL of phosphomolybdenum reagent (0.6 mol M H 2 SO 4 , 28 mM Na 3 PO 4 and 4 mM (NH 4 ) 2 MoO 4 ). To ensure proper diffusion of the phosphomolybdenum reagent, reaction mixture was incubated in a water bath at 95 °C for 90 min. The total antioxidant activity of the composite, as well as that of the vitamin C standard drug, was evaluated at 695 nm using a UV-spectrometer. The total antioxidant activities of the composite were measured in terms of percentage using the following formula where Abs. Cont. and Abs. Sam. are the absorbance of control and absorbance of extract respectively.

Pancreatic α-Amylose Inhibitory Assay (McCue and Shetty Method)
The antidiabetic (α-Amylase inhibitory) activities of synthesized biocomposite derivatives were studied using a modified McCue and Shetty method [30]. The α-amylase inhibitory studies were performed for the test samples and the standard drug acarbose at various concentrations of 10 μg/mL, 50 μg/mL, 100 μg/mL, 250 μg/mL and 500 μg/ mL. 5 ml of test samples were mixed with 2 ml of antidiabetic reagent (20 mM sodium phosphate buffer (pH 6.9), containing 6 mM sodium chloride). Further, test mixtures were incubated with and without α-Amylase (0.5 mg/mL) for about 10 min at 25 °C followed by 1% starch solution was added to the reaction mixture and incubation was continued for 30 min at 25 °C. To stop the enzymatic reaction the colouring agent dinitro-salicylic acid (DNS) was added to the mixture and incubated again for about 5 min in the water bath and were allowed to cool to room temperature. At last, distilled water was added into test mixtures to measure the absorbance using a UV-Visible spectrophotometer at the range of 540 nm.
where Abs. Cont and Abs. Sam are absorbance of control and absorbance of extract respectively.

Drug Loading
The ability to control drug loading and release play the most important role in the development of medical devices. The biological inspiration of biopolymer blended HA and MMT clay composites has been determined through the drug loading / releasing nature of the composites. The drug loading ability of synthesized fishbone polymer matrix was measured by UV-spectrophotometry method. Drug was dissolved in methanol (5:1 w/v) then it was added as drop-by-drop in methanol suspension of polymer composite (20 mg/mL). The mixture was stirred constantly using magnetic stirrer at room temperature. After 24 h, the prepared composite materials were separated by centrifugation. The drug encapsulation efficiency was calculated by measuring the amount of unloaded drug in the supernatant solution at the range of 425 nm for curcumin and 480 nm for doxorubicin using UV-spectrophotometer respectively [31]. The experiments were performed in triplicate. The encapsulation efficiency (%) of prepared composite was calculated using following equation where Wt is the amount of drug added-free non entrapped drug and Wi is the total amount of drug.

Kinetic Studies of In-Vitro Drug Release
The drug release profile of drug-polymer matrix was investigated at different time and pH (5.5, 6.8 and 7.4) using phosphate buffer solution at room temperature. Dialysis tube technique was used to study the in vitro drug release from prepared biocomposite. The prepared biopolymer-drug material was subjected to a 12 kDa (Himedia, Dialysis membrane-110) dialysis membrane tube and also dipped into a beaker containing 30 mL of Phosphate-buffered saline (PBS) buffer. At various time intervals, 1 mL of the supernatant was sample drawn and then 1 mL of fresh PBS buffer was added into the release medium to maintain constant volume. The amount of the released drug was determined by measuring the absorbance of the sampled solution in the range of 425 nm (curcumin) and 480 nm (doxorubicin) using a spectrophotometer at different time intervals [32]. The drug release mechanism was determined by fitting experimental data with several drug release model such as Korsmeyer Peppas, Zero-order kinetics, First-order kinetics and Higuchi equation. The kinetics studies of drug release from biopolymer composite carrier measured using the following equations where M t is theaccumulative amount of drug released at the time (t), M ∞ is the initial drug loading, K is the constant for the drug-polymer system, and n is the diffusion exponent. According to Fickian theory, the profile of drug release includes zero-order kinetics, first-order kinetics and the Higuchi equation.
where F is the a fraction of drug release in time (t) and K 0 is the zero-order drug release constant.
where F is a fraction of drug release in time (t) and K 1 is the first-order drug release constant.
where F is a fraction of drug release in time (t) and K 2 is the Higuchi constant. The equation that allowed for the Zero − order kinetics F t = K 0 t, Higuchi equation F = K 2 t 1∕2 , quantification of drug release from a composite containing the finely dispersed drug.

Fourier Transform Infra-Red (FT-IR) Spectroscopy Analysis
FT-IR spectra were studied for hydroxyapatite (HA), montmorillonite-hydroxyapatite (HA/MMT), sodium alginate-hydroxyapatite (HA/SA) and montmorillonite-sodium alginate-hydroxyapatite (HA/MMT/SA) polymer matrix. Figure 1 shows the FT-IR spectra of the synthesized biopolymer derivatives. The FT-IR spectrum of Fish bone-hydroxy apatite (Fig. 1a) was observed as a broad peak at the range of 3411 cm −1 and 3213 cm −1 which indicates the presence of hydroxyl (-OH) group at phosphate molecule in the compound [33]. The peak at 1635 cm −1 was observed due to the stretching vibration of an adsorbed water molecule. This reveals the hydrophilic nature of fishbone-hydroxy apatite. The sharp infrared peaks at 1089 cm −1 and 827 cm −1 were corresponding to asymmetric and symmetric stretching frequencies of phosphate molecules respectively. Bending vibrations were observed in the range between 599 and 557 cm −1 indicating the presence of a third phosphate molecule in the hydroxyapatite compound [34,35]. The FT-IR spectrum of HA/MMT composite showed in Fig. 1b. A broad peak was found at 3631 cm −1 which indicates the structural -OH stretching frequency of MMT. Another broad peak was observed at 3378 cm −1 , this can be attributed to the hydroxyl group of phosphate in HA [36]. A peak appeared at 1634 cm −1 indicates the hydroxyl  [37]. Figure 1c shows the FT-IR spectrum of Hydroxyapatite-Sodium alginate (HA/SA) composite. FT-IR bands appeared at 824 cm −1 , 462 cm −1 , 1019-1158 cm −1 and 557-599 cm −1 corresponds to wavenumbers (ῡS, δS, ῡaS and δaS) of phosphate groups of the HA [38]. Two more peaks were observed at 660and 1419 cm −1 and this indicates the presence of hydrogen phosphate (HPO 4 2− ) and carbonate (CO 3 2− ) groups respectively. Moreover, due to the presence of hydroxyl ions, the IR bands were appeared at 3274 cm −1 (ῡS) and 557 cm −1 (ῡL) respectively. This revealed the important characteristic peak of the Biopolymer composite [39]. The peaks at 2903 cm −1 and 1597 cm −1 were attributed to the presence of surface water molecules in the hydroxyapatite. The interaction of hydroxyapatite onto Biopolymer (sodium alginate) modified the surface and decreases the intensity of hydroxyl (-OH) bands (ῡS and ῡL) by adding sodium alginate. After the formation of composite, new vibrations bands appeared at 1597 cm −1 , 1333 cm −1 and 1419 cm −1 respectively, this confirms the presence of carboxyl (COO − ) group in SA polymer. The peak observed at 824 cm −1 is attributed to the involvement of triple vibrational modes ((τ (CO), δ (CCO), δ (CCH)) of Ca-alginate. After the insertion of HA in SA, the peak intensity shifted to 824 cm −1 . This wavenumber conversion indicates that sodium alginate has not interacted with P-OH active site of HPO 4 2− groups [40]. The FT-IR spectrum analyzed for the HA/MMT/SA composite was shown in Fig. 1d. The hydrogen-hydrogen interaction on composite has been confirmed by the broad IR bands at 3623 cm −1 and 3213 cm −1 in the polymer which reveals that wavenumbers for hydroxyl of phosphate have been shifted in the IR region in the MMT clay and hydroxyapatite. The peaks were observed at 3070 cm −1 and 1598 cm −1 respectively which indicates the presence of water molecule interaction on the surface of the Biopolymer composite. The peaks at 1420 cm −1 and 1334 cm −1 correspond to the carboxyl group of the polymer Na-alginate.
The IR spectrum of composite shows the characteristics peaks of glycosidic (C-O-C) linkage and absorption band of C-H deformation which corresponds to the vibration of β-pyranose at 1147-1011 cm −1 and 826 cm −1 , respectively. The IR bands have seen around 600 cm −1 , 556 cm −1 and 3521 cm −1 for HA/MMT/SA composite was attributed to the O-P-O bending of phosphate groups and stretching mode of -OH water present in the polymer matrix [41]. Another band shift was observed from 1634 to 1597 and 1598 cm −1 in HA/MMT and HA/MMT/SA composites respectively. This corresponds to -OH bending of a water molecule in MMT clay which further confirms the occurrence of different interactions such as electrostatic interactions and hydrogen bonding, of the Na-alginate with the MMT clay and HA [42] (Table 1).
This supports the presence of MMT clay in the composites HA/MMT and HA/MMT/SA. The discussed wavenumbers for a functional group in the FT-IR spectra confirm the association of MMT and HA have been incorporated successfully in the composite. The FT-IR bands of prepared all composites were shown in Table 1.

X-Ray Diffraction (XRD) Studies
X-ray diffractogram of HA, HA/MMT, HA/SA and synthesized clay blended Biopolymer composites (HA/MMT/SA) were analysed using XRD as shown in Fig. 2. The XRD spectrum of the HA was shown in Fig. 2a (431) show that the prepared HA has crystalline corresponding to Hydroxyapatite [43]. The X-ray diffraction peak of MMT at 2θ = 7° was not observed in the HA/MMT matrix, due to exfoliation. This shown as supportive document in S. Figure 1 [44]. The new diffraction peak was observed at 2θ = 19.76 (d space = 4.48, plane = 100) and 26.85, which shown in Fig. 2b confirmed the formation of a polymeric hybrid structure [45]. After the formation of polymer composite, the crystalline nature of hydroxyapatite was found to decrease due to the interaction of hydrogen atoms. This modification changes the crystallinity to the amorphous state, which had been confirmed through the formation of the aggregated peak from a sharp peak. The value (2θ degree) of the composites was obtained from XRD spectra are shown in Table 2. Figure 2c shows the XRD patterns of the HA/SA composite. A broad peak was found at 26.13° for the polymer sodium alginate, whereas a sharp peak was observed at 32.09° for hydroxyapatite [46]. Apparently, after the inclusion of sodium alginate, the shifting and decreasing in the crystallinity of major peaks of pure Hydroxyapatite, obviously indicates the presence of interaction between alginate and Hydroxyapatite.
Similarly, according to Zhang et al., the intensity of major characteristics peaks of HA/SA was found weak owing the composite was mainly composed through the cross-link reaction of SA on HA [47]. Probably, by adding SA in HA, the interaction between calcium cation (Ca 2+ ) of HA and carboxyl (COO − ) ion of alginate could increase the structural bridges in the Biopolymer composite [48].The crystalline size of the prepared composite was given in S. Table 1 as a supportive document. This confirms the crystallinity of HA was affected after the formation of the composite.
The XRD pattern of Biopolymer hybrid (HA/MMT/ SA) diffraction peaks was observed at 26.57° and 32.15° corresponds to HA and this confirmed the presence of HA in composite (Fig. 2d). Further, the peaks at 23.54° and 26.57° in HA/SA and HA/MMT/SA composite composites were revealed the presence of SA and MMT, respectively [49]. The obtained results concluded that the presence of phosphate (PO 4 3− ) groups on the surface of the HA and enhancing the hybridisation of MMT and resulted in simultaneous interaction of MMT and HA with the carboxylic (COO − ) ions of sodium alginate. Thus, the X-ray diffractograms reveal that the interacting molecules of HA, MMT and SA have been successfully incorporated each other in the Biopolymer hybrid composites. The obtained crystallite value of the prepared compounds reveals the order of amorphous nature of the composites which are shown below HA∕MMT∕SA ≫ HA∕SA ≫ HA∕MMT ≫ HA

Thermogravimetric-Differential Thermal (TGA-DTA) Analysis
Thermal analysis of HA, HA/MMT and synthesized Biopolymer hybrid shown in Fig. 3. The thermal curves of HA were appeared at 81 °C and 230 °C as endothermic peaks, this could be due to the loss of physically absorbed water molecules and the elimination of water lattice in the compound [50].The first mass loss of HA had about 5.40% at 127 °C and this mass loss existed between first and second endothermic peaks. The second mass loss had about 22.14% between 150 and 400 °C, this could be the dehydration of phosphate (HPO 4 2− ) ions molecules due to calcination. The third mass loss had about 3.94% at 780 °C due to the decomposition of HA into the whitlockite phase [51]. The thermal decomposition of HA has been extended due to the presence of calcium (Ca 2+ ) metal ions in the compound and it is shown in Fig. 3a. The TGA-DTA curves of HA/MMT clay composite are shown in Fig. 3b. The mass loss of about 5.38% for HA/MMT composite occurred at the temperature of 95 °C due to the volatilization in the residual water (moisture) molecule and also the water molecules bound at the exchangeable cations in the interlayer space at the composite [52]. The percentage weight loss of the composite at different temperature was shwon in Table 3.
The second mass loss had about 5.89% for composite between 400 and 600 °C due to the dehydroxylation of the structural water of the clay and the loss of water molecules associated with the phosphate groups in HA. The residual mass was found to be 88.71% for the composite, this could be the contribution of un-burnt metal (Na + , K + , Ca 2+ , Fe 2+ , Al 3+ , Si 4+ ) ions in the composite, which extends the thermal stability of the composite more than 800 °C [53].
The thermal degradation for HA/SA composite (Fig. 3c) had about 5.54% at 120 °C, an endothermic peak was observed at 136 °C due to the removal of adsorbed surface water moisture in the Biopolymer composite. Additionally, the exothermic peak showed at 216 °C is corresponds to the breakdown of alginate chains in the hybrid composite, this confirms through the absence of an exothermic peak in the DTA curve of unblended HA (Fig. 3a). Another thermal decomposition was observed between 200 and 400 °C with a weight loss of 29.47%, because of the eruption of the carboxylic (COO − ) group, damage of glycosidic (C-O-C) linkage in the polymer and dehydroxylation of phosphate molecules in HA [54].
Thermal curves of HA/MMT/SA of shown in Fig. 3d. The exothermic peak was observed in the DTA curve at 217 °C due to the thermal decomposition of the alginate chain in the composite. About 10% thermal decomposition for the prepared compounds showed that HA/MMT had more thermal stability than starting material HA and the prepared composites, this might be the reason for non-combustible residual mass and metal ions in the polymer composite. The order of the thermal stability of the prepared compounds were shown below.

Field Emission-Scanning Electron Microscope (FE-SEM) Analysis
The surface morphology of HA and synthesized composite (HA/MMT, HA/SA and HA/MMT/SA) were shown in Fig. 4. Figure 4a shows the morphological surface of HA, which shows irregular particles, with a strong tendency for aggregation. The image showed that particles have been hugely agglomerated in the compound due to the particle-particle interaction of hydroxyapatite [55]. This is further confirmed through a spectrum of EDAX (Ca, P, and O peaks of HA are available) as shown in Fig. 5a. Certainly, the HA is utilized in hard tissue repairing due to structural and chemical properties of hydroxyapatite similar to the mineral phase of bone. The prepared HA/MMT composite composites appeared as porous, the size of pores at 100 nm which is shown in Fig. 4b. Figure 4a showed that the size of the pore has a wide range of distribution ranging in the composite. After the addition of MMT in HA, the size of the pore and the density were found to decrease. This clearly evident the microstructures of HA that the inclusion of MMT had reduced the pore sizes of composite composites (HA/MMT) as compared to pure HA. The absence of agglomeration in the prepared composite indicates that MMT clay particles have been distributed uniformly in the HA compound [56]. The change in the morphological surface of HA confirms the formation of the composite.
Similarly, SEM images of HA/SA possess a wide range of porous structures which are shown in Fig. 4c. The composite prepared in the presence of SA, become agglomerates in  [57]. The modification occurred in the structure due to particle-byparticle interaction and the electrostatic interaction between HA and SA in the composite. The successful association of composite has more preferable to the alteration that occurred in the morphological surface of blended HA on SA. The Biopolymer blended HA/MMT composite microstructure is shown in Fig. 4d. The microstructures of HA were affected due to a decrease in the porous size of particles in the composite composites (HA/MMT/SA) after the addition of MMT and SA in hydroxyapatite respectively. Additionally, SEM micrographs revealed that the composite became homogeneous and rugged after insertion of both MMT and SA particles in the HA and there was also no evidence of agglomeration [58]. This might be the interaction between carboxylic (COO − ) and hydroxyl (OH − ) group of the SA, and the phosphate and Ca 2+ ion of the HA. The physical properties of composite such as rogocity nature, uniformity and firmly assimilation of pathogens are supports for the composite to reveal various biological applications such as antimicrobial, antioxidant, antidiabetic, anti-inflammatory, hemolysis and drug release.

Energy Dispersive Spectroscopic (EDAX) Analysis
The EDAX spectra of HA incorporated derivatives have confirmed the presence of constituents and weight percentage of C, O and metal ions. The EDAX spectrum of HA displays weight percentages of carbon, oxygen, phosphorous and respective metal (Ca 2+ ) ion corresponds for the formed calcium hydroxyapatite (HA) which is shown in Fig. 5a. Figure 5b showed the EDAX spectrum of the matrix MMT clay blended HA [59]. The obtained EDAX spectrum showed decrease in the percentage of calcium and phosphorous and additionally the composite had been possessed silicon ion which confirmed the presence of MMT in the polymer hybrid. Energy dispersive peaks of HA/SA composite showed in Fig. 5c. The peak intensities (cps/eV) were observed with the weight percentage such as carbon-4.5%, oxygen-9.75%, phosphorous-1.19% and calcium-2.08%. This clearly reveals that the percentage of carbon has been increased due to the presence of sodium alginate in a polymer matrix. Similarly, the EDAX peaks for HA/MMT/SA (Fig. 5d) were obtained such as carbon, oxygen, silicon, phosphorous and calcium metal ions were found in the spectrum. The presence of peak for silicon in the spectrum that strongly evident the presence of MMT clay in the composite, the presence of calcium and phosphorous corresponds to the presence of HA in the composite [60]. Moreover, the increase in the percentage of carbon (5.52%) indicates the presence of sodium alginate in the hybrid. The EDAX spectra of the HA derivatives showed strong evidence of the successfully formed composite. The obtained elements weight percentage values were given as supportive documents in S. Table 2.

Ultra Violet-Visible Spectral Analysis
The UV-Vis diffuse reflectance spectra of pure HA derivatives show a redshift of the absorption edges for the composite systems compared to pure hydroxyapatite (HA). The pure HA absorbs only the UV light of less than 350 nm which shows significant contraction than the composites in the UV-Visible region. The extent of redshift depending on the metal ions present in the composite was absorbed in visible light, which has been not exceeded more than 550 nm [61].
The prepared composites showed redshift and strong absorption in both visible and UV-Vis light regions which may enhance the photocatalytic activities in the dye degradation.

Porosity Studies
The prepared HA using fishbone and their derivatives HA/ MMT, HA/SA and HA/MMT/SA were studied for the porosity percentage. The obtained porosity percentage of the compound was compared with the biological studies i.e. the increase in the porosity of the compound showed more activity in biological applications such as antimicrobial, antioxidant, antidiabetic and drug-releasing studies [62]. This may be due to the excessive reactive oxygen species (ROS) formation at the homogeneous and porous surface of substances that might be preferable to induce oxidative stresses leading to cell damage and cell death. The order of porosity percentage for prepared HA derivatives was shown below and the porosity percentage has been given as supportive information in S. Table 3.

Antibacterial Activity
The antibacterial studies were carried out for the prepared HA, HA/MMT, HA/SA and HA/MMT/SA compounds. The antibacterial potential of the composite was evaluated HA∕MMT∕SA > HA∕MMT > HA∕SA > HA. There is no change was occurred in the zones of inhibition around the negative control wells on agar [63,64]. A correlation was observed between the size of inhibition in the zone and concentration of compound i.e. when the diameter of the inhibitory zone increased with increased concentration of compounds. The composite affects more in the bacterial zone of S. aureus and P. aeruginosa and thereby this confirms the composite HA/MMT/SA had more bacteriostatic action than other prepared compounds in the bacterial zone. The minimum and maximum concentrations of prepared test samples and their activity against bacteria were shown in Fig. 6. The maximum inhibition for 250 µL concentration of HA/MMT/SA has affricate well up to 34 mm against the S. aureus bacterial zone [65]. The prepared Biopolymer composite showed significantly antagonistic against all the bacteria and better results than standard drug ampicillin. The increasing order of affected bacterial growth through the prepared HA and their composite derivatives were shown below.

Total Antioxidant Efficacies
The naturally forming free radicals are highly unstable molecules in the human cells, when doing works food converts into energy. Hence, anti-oxidant substances have been used to prevent cell damage in the human cell. The enzymatic and non-enzymatic reaction affects the cells in the human for free radical formation, which leads to occur continuously. The total antioxidant studies showed that the composites exhibit better antioxidant results. The results of percentage inhibition of free radical activity were shown in Fig. 7

Drug Loading and Release Studies
With enhancing the addition of MMT clay and SA in the HA, drug loading percentage was increased due to hydrogen bonding between the carboxylic group of SA, hydroxyl groups of MMT and the amine of doxorubicin and OHgroup of curcumin (Fig. 8a, b). Cumulative drug release rate decreased when compared with drug loading content, this might be related to ionic strength and the more crosslinking agent involvement during the reaction. The variation in the rates and amounts of the drug-releasing ability of drugs could be due to swelling behavior and interaction within the drug-polymer matrix [67]. Curcumin comprising polyphenolic compounds had been extracted from turmeric. Over past decades, many reports have been coming on the work of pharmacological activities like anti-cancer, anti-Alzheimer, anti-diabetic, anti-bacterial, anti-inflammatory and so on. About 79.83% of curcumin drug loaded in the prepared HA/MMT/SA composite had been measured using a UV (Shimadzu UV 3600) spectrophotometric method. In this drug loading and delivery study, the curcumin showed better releases from Biopolymer material than reported studies i.e. for the prepared Biopolymer composite HA/MMT/SA releases 70.12% of curcumin to the target. At pH = 5.5, the curcumin drug-releasing results shows 70.12%, at pH = 6.8 shows 50.85% and at pH = 7.4 shows 34.91%. The change in the drug-releasing ability of curcumin at various pH (5.5, 6.8 and 7.4) is due to the functional group of curcumin that exists in the molecule [68]. Cancer producing cells replicate at pH = 5.5, thus the curcumin, enhancing the releasing rate at pH = 5.5 which is shown in Fig. 8a. This proves the prepared Biopolymer composite might be the better drug-releasing candidate for cancer treatment.
Doxorubicin (DOX) widely employed in chemotherapy treatment, is the most effective chemotherapeutic drug developed against cancer cells such as solid tumors, transplantable leukemia, lymphomas and etc. The doxorubicin drug loaded in the prepared HA/MMT/SA composite had loaded more than curcumin and the drug has been loaded 90.78%. The percentage of drug encapsulation has been more when compared to the drug releases because of the interactions of hydrogen-hydrogen between the OH-group of DOX and the OH-group of polymer hybrid i.e. the drug DOX has been released to the target about 81.18% which is shown in Fig. 8b. At pH = 5.5, the doxorubicin drug-releasing results shows 81.18%, at pH = 6.8 shows 58.06% and at pH = 7.4 shows 35.08% [69].
The change in the drug-releasing ability of doxorubicin at various pH (5.5, 6.8 and 7.4) is due to the functional group of doxorubicin that exists in the molecule. The functional groups on the polymer matrix of HA/MMT/SA enhanced the loading efficiency by the stronger interaction with MMT and SA. Various drug delivery systems are widely in the field of pharmaceutical and biomedical applications. The residual free -COOH groups and OH-in the Biopolymer composite, protonated at acidic pH (5.5), further confirms through the swelling thereby producing greater repulsive force. The obtained results showed better drug release properties for prepared HA/MMT/SA composite than reported compounds. This is shown below in Table 4.

Kinetic Studies of In-Vitro Drug Release
The drug release profiles of curcumin from HA/MMT/SA Biopolymer composite composites carried out at different pH (5.5, 6.8 and 7.4) at 37 °C were graphically represented in Fig. 8a. These three pH values were selected because the drugs might be exposed to those pH conditions while moving through the blood to liver cancer cells. The hybrid composite HA/MMT/SA had more release quantity at pH = 5.5, compared to the pH = 6.8 and pH = 7.4, this hybrid composite HA/MMT/SA had the better-sustained release of curcumin for over 32 h. These results were obtained due  to the participation of numerous -OH and -NH groups between HA/MMT and SA in the composite. The obtained result shows that the release rate in pH = 5.5 was higher than pH = 6.8 and 7.4.The solubility shows higher for both doxorubicin and curcumin due to lower pH, which helps to intake the drug for release to the cells or to the solid tumours, from the HA/MMT/SA incorporated drugs or biomolecules [73]. The decrease occurs in the curcumin drug release due a lower solubility at basic pH (6.8 and 7.4). At lower pH (acidic), the basic (-NH 2 ) centre of curcumin enhances the neutral nature, which has helped to increases the solubility of curcumin.
Similarly, the drug release reports of doxorubicin from HA/MMT/SA Biopolymer composite composites were studied at different pH (5.5, 6.8 and 7.4) at 37 °C and were graphically represented in Fig. 8b. HA/MMT/SA composite had a better drug release amount at acidic pH = 5.5 compare to the basic pH = 6.8 and pH = 7.4 and this Biopolymer hybrid composite HA/MMT/SA released the drug doxorubicin about 76.6% in 32 h. These dramatic changes in the drug-releasing rates might be attributed to the contribution of the hydroxyl group and amine group at the drug, which reduces the drug release rate at basic pH (6.8, 7.4) due to the incorporation between the composite HA/MMT/SA. At lower pH (acidic) increases the solubility of doxorubicin due to the presence of a basic medium of drug and improves the neutral nature [74]. According to kinetic models such as zero-order, first-order, Higuchi and Korsmeyer-Peppas models, the kinetic parameters for both drugs released from the Biopolymer composites were analyzed.
A selecting criterion was the most suitable model R 2 close to unity. At selected all pH the correlation coefficient value (R 2 ) of the Higuchi model was greater than zero-order and the first-order model. The kinetic drug releases for doxorubicin show a value close to R 2 = 0.9939, which fits the Higuchi model. The R 2 values of the Higuchi model for the prepared composites were showed more linearity which indicated that the kinetics drug release of the drugs follows the diffusion-controlled method. The doxorubicin release mechanism was studied using the Korsmeyer-Peppas model. The diffusion exponent values obtained for the composite determine through the Korsmeyer-Peppas model found in the range of 0.5155 to 0.7829 at pH 5.5 indicates that diffusion is anomalous or non-Fickian.
Similarly, the diffusion exponent values were obtained in the range of 0.3483 to 0.4988 at pH 6.8 and 0.1839 to 0.3385 at pH 7.4 respectively for the composites which indicates the drug follows Fickian diffusion behavior with controlled release by diffusion. The kinetic constant (k) value increase when composite content increases, suggesting the diffusion rate increases due to an increase in the size of free spaces in the composite network. The kinetic drug releasing values of curcumin and doxorubicin are given in S. Table.4a and S. Table.4b as supportive information.
At pH = 5.5, the curcumin diffusion exponent value for composites showed the ranges between 0.3889 and 0.4901, drug follows Fickian diffusion and the composite HA/MMT/ SA shows the value 0.6016, indicates coupling of diffusion and matrix erosion mechanism. At pH = 6.8 the composite shows the range between 0.1089 and 0.2509, drugs follow Fickian diffusion. At pH = 7.4 the composite shows the range from 0.1134 to 0.2802, indicates that the drug follows Fickian diffusion [75]. In general, drug release from a polymeric matrix is described by a fickian mechanism when drug diffusion is the main factor in drug release. Diffusion of the drug from a polymeric composite can occur through drug diffusion out of composite. Non-fickian behavior was also found in all pH values (5.5, 6.8 and 7.4). This indicates that diffusion and relaxation of polymer is involved in the drugrelease mechanism.

Antidiabetic Assay (α-Amylase Inhibition
Method) The plot of α-amylase inhibition was evaluated in terms of percentage for prepared Biopolymer composites as shown in Fig. 9. In this analysis, significant differences were found between HA and inserted clay / Biopolymer. Antidiabetic drugs used in diabetes treat diabetes mellitus by altering the glucose level in the blood. These α-amylase inhibitors or starch blocker prevents or slows the absorption of sugar content into the body, mainly blocks the formation oligosaccharides into monosaccharides such as glucose, fructose,  [76]. The obtained α-amylase inhibition results of prepared composites were compared with the standard drug acarbose. The antidiabetic results for the maximum concentration of the compound (HA/MMT/SA) showed 83.96 ± 1.5% and the acarbose was exhibited 80.82 ± 1.6%. The obtained results of the prepared Biopolymer hybrid composite reveals that the composite had more antidiabetic properties than acarbose this might be preferable to utilize as a better antidiabetic drug in the biomedical field. The order of percentage inhibition of α-amylase for the prepared HA, HA/MMT, HA/SA, HA/MMT/SA and the standard drug acarbose were shown below.

Conclusion
The prepared Biopolymer composite HA/MMT/SA was successfully coordinated through the co-precipitation method. The FT-IR and XRD results confirmed the formation of composites. The presence of metal ions in the clay blended Biopolymer derivatives was extended the thermal decomposition of the composites upto 800 °C, this further confirmed through EDAX spectra of the composites. The mechanical properties of composites with exfoliated clays are generally better than composites with intercalated clays. Appropriately, the formation of composite has enhanced the mechanical stability when increase the thermal stability of the composite. After the incorporation of MMT clay and Biopolymer sodium alginate on HA, the morphological surface image was changed. S. aureus bacterial growth HA∕MMT∕SA ≫ Acarbose ≫ A∕MMT ≫ ∕SA ≫ HA had more infected by the prepared composites, the maximum inhibition of HA/MMT/SA have affricate well up to 34 mm against the S. aureus bacterial zone. The antioxidant results for the maximum concentration of the compound (HA/MMT/SA) showed 78.48 ± 2.5% and the vitamin C was exhibited 83.89 ± 2.7%. The results revealed that doxorubicin and curcumin loaded composite has a significant enhancement in drug release ability as compared to pure hydroxyapatite. Drug release showed higher at pH 5.5 compared to the pH 6.8 and 7.4, it has been noticed that the prepared composite reveals a better candidate for modified / controlled drug delivery. Therefore, the prepared composites consisting controlled drug delivery system is preferable to releases the drug as therapeutic agents in a specific target as needed to achieve the desired therapeutic outcome. Moreover, we have planning to carry out our future research works on mineral nucleation, cell adhesion and bone metabolism due to high biocompatibility of hydroxyapatite, calcium ions and other ions associated with biomineralization.