Research Article
Ferrocene-based polyesters with azobenzene linker: Synthesis and biological evaluation
https://doi.org/10.21203/rs.3.rs-2051814/v1
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Ferrocene polymer
azobenzene
cell cyto-compatibility
anticancer activity
antibacterial activity
Cancer represents a class of disease which is the second leading cause of death after cardiovascular diseases [1, 2]. Despite having a variety of cures like chemotherapy and thatmeans of treatment. Chemotherapeutics are the cytotoxic agents that are developed to cause toxicity to the selective cancer cells with minimal effects to the normal cells. In addition to the cancer, infections caused by the resistant microorganisms are difficult to cure by conventional treatments, resulting in prolonged illness and greater risk of death, thus developing a need to synthesize drugs which could minimize both the growth of cancerous cells and microorganisms. However, it is important that the treatment should be cell cyto-compatible i.e., harmless to the healthy cells [4].
Ferrocene based materials have attracted active interest in recent years within the field of medicinal and bio-organometallic chemistry [5]–[9]. The organometallic analogues of antimalarial drug chloroquine (derivatives of the ferroquine) and the breast cancer drug tamoxifen (ferrocifen) being the most widely known ferrocene based cures [10, 11].
Azobenzene derivatives have widely been explored in optoelectronics based on their fascinating optical properties[12]–[14]; however, there are very few papers on the biological properties focusing anti-cancer and antibacterial activities of the material [15]–[17]. It is known that the ferrocene and azobenzenes, alone, have incredible biological activities and have important applications as anti-cancerous, antibacterial and antifungal activities, thus, the idea was to synthesize material having both functionalities in them and to explore their biological activities. In addition to the aforementioned groups, the presence of aromatic and aliphatic moieties in chain could also affect the properties of material [18]–[21]. In addition incorporation of different aliphatic diols along with aromatic diols in parent macromolecules ensures their better solubility and hence could enhance their utility for biological systems [11], [22, 23].
In the presented work, a series of aromatic and aliphatic ferrocene-based poly(azobenzene)esters (PABEs) were synthesized by solution poly-condensation process. In order to improve the solubility, to study the structure property relationship and to explore the biological behavior, various aliphatic and aromatic units were incorporated in the polymer backbone.
Ferrocene (m.p = 172 − 174°C, Fluka), acetyl chloride (b.p = 51 − 52°C, Fluka), thionyl chloride (b.p = 74.6°C, Fluka), aluminum chloride (m.p = 192.4°C, Fluka), 4-aminophenol (m.p = 188 − 190°C, Fluka), 1,2-ethandiol, (b.p = 195–198°C Sigma-Aldrich), 1,4-butandiol, (b.p = 230°C, Sigma-Aldrich), 1,6-hexandiol (b.p = 250°C, Sigma-Aldrich), phenol(m.p = 40.5°C Sigma Aldrich) 1-naphthol (m.p = 95–96°C Merck), biphenyl-4-ol(m.p = 162–165°C Merck) were used as received. The solvents (dichloromethane, diethyl ether, tetrahydrofuran and dimethyl sulfoxide (Sigma-Aldrich) were dried according to the reported method [24].
Melting point was determined on Mel-Temp, (Mitamura Riken Kogyo, Inc. Tokyo Japan) using open capillary tubes. The Fourier Transform infrared spectra in solid state were recorded on a Thermo Scientific Nicolet-6700 FTIR spectrophotometer. The UV-visible spectra of synthesized monomers and polymers solutions in THF and DMSO, using quartz cells were obtained using a 1601-Schimadzu. 1H NMR spectral analysis of monomers were carried out in DMSO solvent by using of Bruker Advance ultra-shield 300 MHz digital NMR instrument using TMS as internal reference. Viscometric records of the polymers were collected using a U-tube Ubbelohde’s viscometer having 20 mL volume in NMP solvent at room temperature to evaluate the molecular weight of polymers. Cells were incubated with the live/dead solution in dark for 30 minutes prior to imaging, carried out by using fluorescence microscope (Axiovert 40CFL, filter set 23, Zeiss, Thornwood, NY) fitted with a digital camera (SPOT Insight 1120, or SPOT Idea 2920, Diagnostics Instruments, Sterling Heights, MI) and an inverted TE2000-E microscope (Nikon, Melville, NY) outfitted with a Cool Snap HQ2 (Photo metrics, Tucson, AZ) digital camera.
a. Cell cyto-compatibility:
Cell cytotoxicity was tested by L-929 (fibroblast mouse cells) using life dead assay. Live/dead imaging was performed to evaluate cell viability qualitatively. Before the addition of live/dead stain, cells were washed with phosphate buffer saline solution (PBS) to remove any remaining culture media and fetal bovine serum (FBS). Cells were incubated with the live/dead solution in dark for 30 minutes prior to imaging which was carried out by using fluorescence microscope. Control was kept in the incubator with each measurement to compare the cell activity. Cells cultured under normal conditions without using any material were used as a blank control. The control had ability to facilitate 100% growth of the normal cells. Experiments were repeated three times to exclude any doubt or coincidence [25].
b. Antibacterial assay:
Antibacterial activity of poly(azobenzene)-esters (P12F, P14F, P16F, P22F, P24F, P26F, P32F, P34F, P36F) was monitored against E. coli and was evaluated by cell number measurement in triplicate by counting of healthy cell nuclei with array scan after Hoechst 33342 stain. The testing protocol is comprised of 5 days and is given below.
i) Day 1: Bacteria were cultured overnight at 37°C.
ii) Day 2: 0.086D of bacterial culture was put in lysogeny broth (LB) medium with dilution factor of 1:50 with the material. Solution was mixed for 15sec in centrifuge at 1300rpm and left for next 2 days.
iii) Day 5: Bacteria were counted by Teca reader [26].
c. Anticancer activity:
Anticancer activity of poly(azobenzene)-esters (P12F, P14F, P16F, P22F, P24F, P26F, P32F, P34F, P36F) was monitored against HepG2. Activity was evaluated by cell number measurement in triplicate by counting healthy cell nuclei with array scan after Hoechst 33342 stain. Testing protocol for the anticancer activity is comprised of 5 days and the detail is given below.
i) Day 1: Cell seeding was carried out by taking 2000 cells/well in 40µl RPMI /10% FBS in 384well plate. Incubation was carried out for 24h at 37°C.
ii) Day 2: Polymer solutions were transferred on 2nd day. The cells were seeded for the next two days.
iii) Day 5: First, cell fixation was carried out by adding 40µl/well 4% PFA (Paraformaldehyde) by using a dispenser in HepG2cells and which was then incubated for one 1h at room temperature. At the end, cell number was counted by Teca reader.
Unless stated, all reactions were performed under a N2 atmosphere in a vacuum line.
a. Synthesis of Monomers (1, 2 and 3):
1.1′ Ferrocene dicarboxylic acid chloride was prepared by the reported method [19]. Azobenzene diols (1, 2 and 3) were prepared by a method given in literature with slight modifications [27]. Aromatic diamine was taken in stoichiometric amount (328 mmol) in a 250 mL beaker having a magnetic stirrer. A warm HCl solution (37%) was added to the corresponding amine at 0–5°C which was attained using ice bath. The suspension was stirred vigorously until fine crystals of aromatic diamine hydrochloride were separated out. A cold sodium nitrite solution (108 mmol) in 10 mL water was added slowly to this mixture. The coupling reagent (phenol/napthol/biphenyl 4-ol) (72 mmol) was dissolved in NaOH solution (821mmol in 100 mL water) and ice cooled using ice bath. The azotized solution was added slowly to this solution afterwards while stirring. The mixture was then acidified by 10% \({H}_{2}S{O}_{4}\) solution. The resulted precipitates were filtered using Buchner funnel. Solid was dissolved in 10% NaOH and precipitated by 10% \({H}_{2}S{O}_{4}\) which were recrystallized in ethanol/methanol to get the pure diols.
4,4'-Bis(4-azo-1-hydroxybiphenyl)biphenylether (1)
4,4'-Bis(4-azo-1-hydroxybiphenyl)biphenylether (1) was prepared by using aforementioned method. For this purpose, 4, 4’-Oxydianilne (7.2 g, 36 mmol) was reacted with the coupling reagent biphenyl 4-ol (12.25g, 72 mmol) and the product was recrystallized in ethanol/methanol to get the pure product.
Yellow powder; 81%, m.p. 225 oC, UV/vis (nm): 350, FTIR (cm− 1) 3385 (OH), 3024 (aromatic C-H), 1594 (-N = N-), 1274 (C-O-C), 839 (Biphenyl C-H bend). 1HNMR [(DMSO-d6) δ(ppm): 6.86 (4H, d, 8.8), 7.27 (4H, d, 7.2),7.38 (4H, d, 7.9),7.47(4H, d, 8.7), 7.49 (4H, d, 7.5),7.55 (4H, d, 8.1), 9.55 (OH, s). Elemental analysis, C36H26O3N4 (MW = 562) in wt% calculated (C 76.87, H 4.62, N 9.96), found (C 76.21, H 4.01, N 9.80).
4,4'-Bis(4-azo-1-hydroxynaphthyl )biphenylether (2)
4, 4’-Oxydianilne (7.2 g, 36 mmol) was coupled with 1-naphthol (10.36 g, 72 mmol) by using the procedure given above to yield the product which was finally recrystallized in ethanol/methanol.
Black powder; 79%, m.p. 150 oC, UV/vis (nm): 416, FTIR (cm-1) 3358 (OH). 3016 (aromatic C-H), 1580 (-N = N-), 1237 (C-O-C), 832 (naphthol C-H bend), 1HNMR [(DMSO-d6) δ(ppm): 7.01 (2H, d, 8.4), 7.11 (4H, d, 8.9), 7.30 (2H, t, 7.27), 7.57 (2H, t, 7.58), 7.67 (2H, d, 8.9), 7.87 (2H, d, 8.7), 7.90 (4H, d, 8.7), 8.05 (2H, d, 8.03), 9.31 (OH, s). Elemental analysis, C36H26O3N4 (MW = 562) in wt% calculated (C 75.21, H 4.31, N 10.98), found (C 75.10, H 4.09, N 10.79)
4,4'- Bis(4-azo-1-hydroxyphenyl)biphenylether (3)
4, 4’-Oxydianilne (7.2 g, 36 mmol) phenol (6.76 g, 72 mmol) were reacted by using the procedure given above to yield 4,4'-Bis(4-azo-1-hydroxyphenyl)biphenylether (3)
Green powder; 79%, m.p.180oC, UV/vis (nm): 364, FTIR (cm-1) 3407 (OH).3052 (aromatic C-H), 1581 (-N = N-),1266 (C-O-C), 840 (phenyl C-H bend).1HNMR [(DMSO-d6) δ(ppm): 6.94 (2H, d, 8.7), 7.23 (2H, d, 9.0), 7.77 (2H, d, 8.7), 7.87 (2H, d, 8.7), 10.31 (OH, s,). Elemental analysis, C36H26O3N4 (MW = 562) in wt% calculated (C 70.24, H 4.39, N 13.65), found (C 70.21, H 4.43, N 12.95).
b. Synthesis of Polymers (P12F, P14F, P16F, P22F, P24F, P26F, P32F, P34F, P36F):
Poly(azobenzene)-esters were synthesized using polycondensation method by reacting aromatic and aliphatic diols with diacid chlorides in the molar ratio 1:1:2. The corresponding azobenzene diol monomer and aliphatic diols (3.2 mmol) in 15 mL of THF (freshly dried) taken in a prebaked two necked flask fitted out with condenser and magnetic stirrer. 10 mL of trimethylamine was added to the reaction mixture and the temperature of the reaction was maintained at 0oC by using ice bath. Respective acid chloride (3.2 mmol) in 20 mL of dry THF was added drop wise to the reaction mixture with vigorous stirring. The temperature was raised up to room temperature gradually. The reaction mixture was stirred for 20 hours and then refluxed further for 1.5 hour. It was then filtered when reached to ambient temperature. The precipitates obtained were washed several times with THF, water and methanol to get the corresponding polymer. The powdered products were vacuum dried for 24 hours (The polymers are coded as: e.g., For P12F, P = Polymer, 1 = R(1), 2 = R’(2) and F = ferrocenyl, scheme 1 ).
P12F: 844; Black; 84%. UV/vis (nm): 354. FTIR (cm− 1): 3178 (aromatic C − H), 2961 (aliphatic C − H), 1749, 1716 (C = O), 1542 (N = N), 1216, 1026 (C − O-C), 512 (ferrocenyl). 1HNMR [δ, deuterated dimethyl sulfoxide (DMSO-d6)]: δ (ppm): 8.1–6.9 (aromatic), 5.0 − 4.4 (b, ferrocenyl), 2.3-2.0 (4H, s, methylene). Anal. Calcd: C, 71.82; H, 4.08; N, 6.51. Found; C, 71.39; H, 4.02; N, 6.60.
P14F: 872; Black; 89%. UV/vis (nm): 352. FTIR (cm− 1): 3154 (aromatic C − H), 2970 (aliphatic C − H), 1738, 1709 (C = O), 1540 (N = N), 1228, 1012 (C − O-C), 509 (ferrocenyl). 1HNMR [δ, deuterated dimethyl sulfoxide (DMSO- d6)]: δ (ppm): 8.3–6.8 (aromatic), 4.8 − 4.5 (b, ferrocenyl), 2.4–2.1 (8H, m, methylene). Anal. Calcd: C, 71.15; H, 4.57; N, 6.34. Found; C, 71.50; H, 4.45; N, 6.41.
P16F: 900; Black; 82%. UV/vis (nm): 354. FTIR (cm− 1): 3137 (aromatic C − H), 2973 (aliphatic C − H), 1741, 1715 (C = O), 1583 (N = N), 1207, 1055 (C − O-C), 518 (ferrocenyl). 1HNMR [δ, deuterated dimethyl sulfoxide (DMSO- d6)]: δ (ppm): 8.3–6.9 (aromatic), 4.7 − 4.2 (b, ferrocenyl), 2.2–2.4 (12H, m, methylene). Anal. Calcd: C, 72.31; H, 4.94; N, 6.15. Found; C, 72.01; H, 4.81; N, 6.24.
P22F: 792; Maroon; 90%. UV/vis (nm): 414. FTIR (cm− 1): 3140 (aromatic C − H), 2935 (aliphatic C − H), 1745, 1708 (C = O), 1575 (N = N), 1225, 1056 (C − O-C), 542 (ferrocenyl). 1HNMR [δ, deuterated dimethyl sulfoxide (DMSO- d6)]: δ (ppm): 8.2–6.8 (aromatic), 4.5 − 4.1 (b, ferrocenyl), 2.3–2.5 (4H, m, methylene). Anal. Calcd: C, 69.54; H, 4.39; N, 7.26. Found; C, 69.69; H, 4.04; N, 7.38.
P24F: 820; Maroon; 88%. UV/vis (nm): 390, FTIR (cm− 1): 3071 (aromatic C − H), 2972 (aliphatic C − H), 1732, 1712 (C = O), 1583 (N = N), 1229, 1098 (C − O-C), 508 (ferrocenyl). 1HNMR [δ, deuterated dimethyl sulfoxide (DMSO- d6)]: δ (ppm): 8.4–6.9 (aromatic), 4.6 − 4.4 (b, ferrocenyl), 2.2–2.4 (8H, m, methylene). Anal. Calcd: C, 69.99; H, 4.65; N, 6.89. Found; C, 69.72; H, 4.39; N,6.92.
P26F: 792; Maroon; 84%. UV/vis (nm): 414. FTIR (cm− 1): 3154 (aromatic C − H), 2913 (aliphatic C − H), 1778, 1704 (C = O), 1565 (N = N), 1266, 1048 (C − O-C), 514 (ferrocenyl). 1HNMR [δ, deuterated dimethyl sulfoxide (DMSO- d6)]: δ (ppm): 8.2–7.1 (aromatic), 4.6 − 4.4 (b, ferrocenyl), 2.0-2.2 (12H, m, methylene). Anal. Calcd: C, 70.14; H, 4.87; N, 6.45. Found; C, 70.75; H, 4.71; N, 6.60.
P32F: 668; Green; 91%. UV/vis (nm): 364. FTIR (cm− 1): 3142 (aromatic C − H), 2970 (aliphatic C − H), 1736, 1706 (C = O), 1581 (N = N), 1235, 1097 (C − O-C), 510 (ferrocenyl). 1HNMR [δ, deuterated dimethyl sulfoxide (DMSO- d6)]: δ (ppm): 8.2–6.8(aromatic), 4.7 − 4.4 (b, ferrocenyl), 2.4–2.5 (4H, m, methylene). Anal. Calcd: C, 64.77; H, 4.25; N, 8.64. Found; C, 64.60; H, 4.19; N, 8.87.
P34F: 696; Green; 87%. UV/vis (nm): 358. FTIR (cm− 1): 3165 (aromatic C − H), 2949 (aliphatic C − H), 1745, 1719 (C = O), 1581 (N = N), 1266, 1048 (C − O-C), 510 (ferrocenyl). 1HNMR [δ, deuterated dimethyl sulfoxide (DMSO- d6)]: δ (ppm): 8.0-6.4 (aromatic), 5.1–4.6 (b, ferrocenyl), 2.4–2.5 (8H, m, methylene). Anal. Calcd: C, 65.78; H, 4.92; N, 8.45. Found; C, 65.72; H, 4.59; N, 8.60.
P36F: 724; Green; 85%. UV/vis (nm): 360 FTIR (cm− 1): 3126 (aromatic C − H), 2945 (aliphatic C − H), 1765, 1724 (C = O), 1587 (N = N), 1224, 1025 (C − O-C), 502 (ferrocenyl). 1HNMR [δ, deuterated dimethyl sulfoxide (DMSO- d6)]: δ (ppm): 8.1–6.9 (aromatic), 4.8 − 4.2 (b, ferrocenyl), 2.3–2.5 (12H, m, methylene). Anal. Calcd: C, 65.78; H, 5.08; N, 7.94. Found; C, 66.52; H, 4.97; N, 7.98.
The diol-terminated azobenzene based monomer required for preparing polymer material was synthesized by a reported method [27]. Poly(azobenzene)esters were synthesized using low temperature solution polycondensation of monomers (1, 2, 3 and 2, 4, 6) and the diacid chlorides (F), Scheme 1. The purpose of incorporation of different aliphatic and aromatic diols in parent macromolecules was to ensure better solubility and study of structure − property relationship [28]. The targeted material was prepared by combining stoichiometric amount of the monomers in one-pot three-reactants employing in situ process. The reaction was carried out at atmospheric temperature and pressure to avoid any side reaction and decomposition of thermally sensitive monomers. Low reflux temperature was essential to avoid the decomposition of reactants and side reactions [28]. All polymers were found soluble in common organic solvents.
Spectroscopic studies
The UV/visible spectra were recorded qualitatively in THF at room temperature to confirm the presence of different groups in the Fe-PABEs chain. The polymers were dissolved in THF to make dilute solutions for the study. All the polymers showed prominent λ max peaks due to π→ π* electronic transitions around 350–420 nm and a low intensity n→ π* band in between 420- 500nm. There are different side groups attach in each of the polymer chains so we observe a small variation in the λ max due to these variable side groups differencing in chain length attached to the main azo group [29].
FTIR and 1HNMR spectroscopy were used to confirm the important functional groups present in the monomers (1, 2, 3) and polymers (P12F, P14F, P16F, P22F, P24F, P26F, P32F, P34F, P36F).
In FTIR spectra, major changes were observed in the spectral signals of initial and final products as some of the signals disappeared and some new appeared in the product. The FTIR spectrum of azo monomers showed a strong peak around 3400(s) cm− 1 indicating the presence of hydroxyl group at the terminals. The absence of a sharp C = O peak in the region 1700 − 1720 (s) cm− 1 along with the presence of a peak at 1584 (s) cm− 1 showed that amine has been transformed to azo linkage (N = N) [30].
The spectra of poly(azobenzene)esters (PABEs) showed all the characteristic bands expected for assumed structures. The presence of absorption bands expected for the ester linkage (C = O), (C − O) along with the peak for azo group appeared in the ranges 1708 − 1765 (s), 1012 − 1266 (s), and 1542 − 1587 (s) cm− 1, respectively, showed the formation of PABEs [16]. In addition, the absence of a broad peak for the OH group, around 3400 cm− 1 coincident with the appearance of a band for diacid chloride group in the region of 785 − 535 cm− 1 confirmed the presence of C − Cl group at the terminal of polymer chains.
In the case of terpolymers, the above-mentioned peaks for ester and azo appeared as symmetric doublet peaks representing successful incorporation of diols in the parent chain. Additional absorption bands related to the functional group present in the diols added to the chain were found in each spectrum in their respective regions, e.g., C − H aliphatic appeared around 3000 − 2900 cm− 1 in the spectra of all polymers, as a part of their chain. Aromatic C − H appeared around 3100 cm− 1in all polymers.
1H NMR spectra of the monomers recorded in DMSO exhibited all the characteristic signalsconfirming the diol terminal group with azo linkage in the product [16]. The spectra of the Fe-PABEs were recorded under similar conditions. The 1H NMR spectra showed all the signals necessary for the confirmation of polymer backbone. The cyclopentadienyl protons appear in the range 4.30 − 5.1 ppm. Some signal broadening in 1H NMR spectra indicated the presence of paramagnetic impurities because of oxidation of ferrocene into the ferrocenium ion as reported in literature. The multiplets for aromatic protons appeared in the range of 6.4–8.9 ppm [16] whereas characteristic signal corresponding to the aliphatic proton appeared in the range of 1.5–2.5 ppm in the 1H NMR spectra of the respective polymers[31].
The stoichiometry of the monomers and PABEs was confirmed by elemental (C, H, N) analysis which showed a good correlation between the proposed structures and the experimental results. The calculations were made based on the structure of repeat unit present in the polymer chain. The elemental analysis showed that in each polymer, monomers were in equimolar proportion. However somewhat higher contents of carbon found may be because of ferrocenyl acid group which was not included in calculations [31].
Molecular weights of the polymers were calculated by viscosity measurements. Viscometric records of the polymers were collected using a U-tube Ubbelohde’s Viscometer working on gravimetric capillary principle tabulated in Table 1. Molecular weight measurements were carried out using Mark–Houwink equation [20] and were found to be in between 84000–99000 g/mol showing they have high molecular weights [31].
Polymer |
Mw(g/mol) |
Polymer |
Mw(g/mol) |
Polymer |
Mw(g/mol) |
---|---|---|---|---|---|
P12F |
97816 |
P22F |
98895 |
P32F |
96421 |
P14F |
98421 |
P24F |
99281 |
P34F |
96771 |
P16F |
98594 |
P26F |
99539 |
P36F |
97174 |
*NMP = N-Methyl-2-pyrrolidone |
3.1 Bio screening: Bio screening of the synthesized PABEs was carried out by measuring cell cyto-compatibility against L929 fibroblasts, antibacterial activity against E. coli and anticancer activity against Hep-G2cancerous liver cell line.
Cell cyto-compatibility: Cytotoxic effect of the synthesized PABEs was monitored against fibroblast (L-929) mouse cells using Live/dead assay. The lack of cytotoxic response to indirect culturing with poly (azobenzene) esters was visually confirmed (Fig. 1) and no documented changes in morphology were observed compared to the non-cytotoxic control or the blank culture media. The entire poly (azobenzene) esters series showed good compatibility with L-929 Fibroblast at a given concentration. The quantification of viable cells in all the three esters have shown the results comparable to control. The P12F and P14F have shown more than 50% viability which suggests their therapeutics potential (Fig. 2)
Antibacterial activity: The in vitro anti-bacterial activity of the PABEs was carried out against the gram negative Escherischia.Coli (E. coli). Results indicated in Fig. 3A and Table 2.
The value of Hill coefficient has shown the positive cooperativity of binding between the polymers and E. coli in most of the cases. Highest activity difference observed in E. coli cell growth is by P12F, which is 52% which, is attributed to highest aromaticity of polymer. Decline in activity difference is observed with addition of more soft spacers, which dilute the polymer conjugation and hence decrease the activity. The results are presented as mean activity difference of PABEs
Polymer |
Activity difference (%) |
IC50((µM) |
Hill coefficient |
---|---|---|---|
P12F |
52 |
0.077 |
0.6 |
P14F |
41 |
0.15 |
0.99 |
P16F |
13 |
0.13 |
2 |
P22F |
39 |
0.023 |
1.4 |
P24F |
38 |
0.021 |
1.4 |
P26F |
29 |
0.024 |
1.3 |
P32F |
19 |
0.0048 |
1.5 |
P34F |
18 |
0.004 |
1.6 |
P36F |
27 |
0.0049 |
1.1 |
Anticancer activity: Chemoprevention is now regarded as a promising strategy to control cancer [6]. Successful drug treatment of a human disease requires an adequate therapeutic index reflecting the treatment’s specific effects on target cells and its lack of clinically significant effects on the host. Anticancer studies of the synthesized polymers were carried out against Human liver cancerous cells (Hep-G2). Activity difference was determined to see the effect of the tested material on the cancerous cell, Fig. 3B, Table
Polymer |
Activity difference (%) |
IC50((µM) |
Hill coefficient |
|
---|---|---|---|---|
P12F |
12 |
0.00078 |
0.3 |
|
P14F |
180 |
0.00052 |
-0.1 |
|
P16F |
70 |
0.00051 |
-0.3 |
|
P22F |
45 |
0.25 |
1.6 |
|
P24F |
28 |
0.095 |
0.8 |
|
P26F |
27 |
0.19 |
1.2 |
|
P32F |
40 |
0.0062 |
0.12 |
|
P34F |
9.7 |
0.24 |
3.2 |
|
P36F |
50 |
0.44 |
2.2 |
Anticancer data Fig. 3B shows good results in terms of activity difference. Highest activity difference was observed by P14F and it shows negative cooperativity of binding with the cancerous cells. Polymer P14F showed the highest significance in decreasing the activity of cancerous cells. Majority of the polymers in above mentioned series showed positive cooperativity with the cancerous cells (HepG2). The abovementioned results indicate the good anticancer activity of the tested polymers against Hep-G2.
A series of soluble ferrocene-poly (azobenzene) esters consisting of aromatic and aliphatic spacers were synthesized and characterized successfully. Biological screening of the synthesized PABEs were conducted to determine cyto-compatibility, antibacterial and anticancer activity. Significant antibacterial, non-cytotoxic and anticancer activities indicated their potential to be used as antibiotic and anticancer agents. These polymers can be further studied for different pharmacological activities, to be used as potential drug candidates.
From all the above-mentioned studies, it was concluded that the incorporation of different units is very useful strategy to improve the properties of polymeric materials, like solubility and biological activity.
Author is highly obliged to HEC of Pakistan for providing the funding for the research. Also owe a special thanks to Dr. Jens Peter von Kries and Dr. Martin Neuenschwender (Leibniz institute of molecular pharmacology, Berlin, Germany) for providing all the facilities and assistance for the biological studies.
Scheme 1 is available in supplementary section.
No competing interests reported.
Scheme 1: Synthesis of Poly (azobenzene)-esters (PABEs) (The polymers are coded as: e.g., For P12F, P=Polymer, 1= R(1), 2=R’(2) and F= ferrocenyl )
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