In recent years, polymer nanoassemblies have played an important role in the biopharmaceuticals field. Polymers that form different molecular architectures during a self-assembly process are widely used for a large number of biomedical applications, including as drug carriers, imaging agents, and drug reservoirs, thereby providing a local therapeutic effect. The size and shape of these nanoassemblies play vital roles in cell penetration. Importantly, stimuli-responsive behaviors, particularly pH responses, make these systems highly suitable vehicles for drug, gene, and protein delivery applications. This platform can be used for precise control over polymer assembly behavior under diverse pH conditions. In this Review, we discuss the pH-responsive behavior of a wide variety of amphiphilic homopolymers and block and random copolymers that form a sample range of nanoaggregates due to the self-assembly of hydrophilic−hydrophobic building blocks.

Stimuli responsive polymeric nanocarrier (RCOP-2) functionalized with frontline antituberculosis drug (Rifampicin) is demonstrated for sustained release. Bioavailability of Rifampicin is taken care of by conjugating this drug through a acylhydrazine linker to the polymeric backbone. The poly(ethylene glycol) structural motif is introduced in the copolymer architecture for water solubility. Releasing retinal along with Rifampicin is hypothesized to reduce the risk of side effects due to Rifampicin. The self-assembly of RCOP-2, due to the amphiphilicity present in the copolymer, is explored in detail. The pH responsiveness of RCOP-2 is demonstrated in mild acidic environment as well as in cell lines. The 4T cell line, due to its acidic nature, shows time-dependent cellular internalization. On the basis of the results, our unique design is expected to provide an increased bioavalaibility of Rifampicin with reduced side effects. From the flow cytometry results on A549 cell lines, it is clear that the newly designed copolymer RCOP-2 can internalize efficiently and serve as an effective Rifampicin delivery system.

A novel library of norbornene derived helical copolymer has been synthesized through the coupling of two homopolymers via Molecular Marriage Approach. The helicity is governed by the non-covalent interactions like hydrogen bonding, π-π stacking and the influence of hydrophobic and hydrophilic motifs. The detailed characterization of the copolymer (Copoly 1) has been provided and the super structures are confirmed through dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The observed size of the aggregates was about 200 nm. The density functional theory (DFT) is favorably supported for the formation of proposed structure of Copoly 1. Circular dichroism (CD) measurement has confirmed the one handed helical structure of the copolymer. Reservoir capability of this pH responsive polymer (Copoly 1) to encapsulate anti-cancer drug doxorubicin (DOX) warrants its potential applications in the field of bio-medical sciences.

Aliphatic polyamides containing pendent allyl groups were prepared by anionic ring-opening copolymerization of ε-caprolactam with monomer 1, the substituted lactam 3-(3-propenyl)-2-azepanone. Copolymerization experiments revealed that up to 11 mol % of 1 was integrated successfully into these novel polyamides, which ranged in molecular weight from 27 to 72 kDa. Relative to the well-known commercial polyamide-6 (PA-6), the degree of crystallinity of the copolymers decreased with incorporation of functional monomer. Moreover, the pendent allyl groups afforded rapid access to numerous functional aliphatic polyamides, using photoinitiated thiol–ene chemistry, providing a pathway to cross-linked polyamide films and gels.

Aim: Our aim was to synthesis and characterization of amphiphilic norbornene-derived thiobarbiturate homopolymers (NDTH 1–4) for drug delivery. Methods: Ring-opening metathesis polymerization technique was used to prepare a series of homopolymers. The hydrophobicity is introduced by increasing the number of carbon chains ([-CH2-]n; n = 1, 2, 3 & 4) in between norbornene backbone and thiobarbiturate species. Results: These vesicular aggregates have been used as anticancer Doxorubicin drug delivery vehicles at the acidic (5.5) and physiological (7.4) pHs. Confocal laser-scanning microscopy has demonstrated that the drug-loaded vesicles are easily internalized into living cells. Conclusion: Amphiphilic norbornene-derived thiobarbiturate homopolymer assemblies showed efficient nanocarrier for effective anticancer drug delivery.