Antibacterial Activity of Amphiphilic Polymers

Manish Kumar Rawal, Nishigandh Sunil Pande, 

Yuvraj Kunwar Jhala, Kamalendra Singh Chouhanand Narendra Pal Singh Chauhan 

Peptides are also amphiphilic polymers, i.e., mostly positively charged molecules with short amino acid chains, and are a key component of the innate immune system. The focus on amphiphilic polymers is due to some reports suggesting that the current global drug pipeline is woefully inadequate due to bacterial resistance to antibiotics [3]. The application of amphiphilic polymers and their block polymers to stop the microbial growth of infected tissue has been reported in the literature [4]. 

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Peptides exhibit the highest antimicrobial activities of amphiphilic polymers and also possess antibacterial, antiviral, antifungi and anticancer activities [30-32]. In view of the potential applications of peptides, we will now discuss the synthesis of some important antibacterial peptides. Gad-1 and Gad-2 are peptides with amino acid chains and are prepared using O-fluorenylmethyloxycarbonyl (Fmoc) chemistry. 

To measure the antibacterial activities of amphiphilic cationic polynorbornene derivatives, they developed a slightly different method based on optical density (OD). In this method, bacteria were grown in suspensions (Escherichia coli D31 and Bacillus subtilis ATCC 8037 ) of Miieller-Hinton broth (MHB) overnight at 37 °C, diluted with fresh MHB to an OD of 0.1 at 600 nm and further diluted by a factor of 10. This suspension was mixed with different concentrations of freshly prepared polymer solutions in rm-buffered saline (pH 6.5-7.0), by serial dilution in a 96-well plate, and incubated for 6 h at 37 °C. The OD 600 nm was measured for bacteria suspensions that were incubated in the presence of a polymer solution or fm-buffered saline only. After 6 h, the MIC for 90% inhibition of growth was determined. 

Liposomes provide simplified models for bacterial and mammalian cell membranes, although they underestimate several factors such as cell walls and lipopolysaccharides in bacterial cell membranes. However, our results from membrane disruption activities of amphiphilic polymers built a strong foundation for structure-property relationships of these materials and warrant further exploration of antibacterial activities as well as any other relevant biomedical application of these polymeric materials. 

Methyl methacrylate (MMA) and sodium styrene sulfonate (SSNa) are water-soluble. These polymers behave like a low MW surfactant as they form micelles in aqueous solution in which the hydrophobic part is directed towards the centre and the hydrophilic part is situated on the periphery of the micelle. Owing to such features, amphiphilic block copolymers have wide-ranging applications in drugs, pharmaceuticals, coatings, cosmetics and paints. They also exhibit very high antibacterial activities. Oikonomou and co-workers used ATRP to prepare amphiphilic block copolymers, consisting of polymethyl methacrylate (PMMA) and poly (sodium styrene sulfonate) (PSSNa) blocks [18]. The synthesis methods are described below. 

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