Natural biopolymers such as proteins and nucleic acids in living organisms possess an inherent ability to respond to local environmental stimuli, which motivated researchers to make biomolecule-derived non-biological macromolecules with a biomimetic structure having stimuli-responsive properties. This review mainly focuses on stimuli-responsive polymers having natural amino acid units either in the main-chain or in the side-chain, their self-assembled nanostructures and hydrogel networks. Recent advances in the design and synthesis of amino acid-derived polymers that are responsive to various physical, chemical, or biochemical stimuli such as temperature, light, pH, redox-, metal ions, gas, glucose, enzyme, proteins, DNA or a combination of these are illustrated. Their potential for use as stimuli-responsive “smart” nanomaterials in biomedical and biotechnological applications such as in controlled drug delivery, gene delivery, non-fouling materials, etc. is also highlighted. The primary aim of this review article is to motivate researchers towards the design and synthesis of novel stimuli-responsive biohybrid materials for making next generation smart materials.

Traditional luminescent polymers typically contain extended π–π conjugated structures that suffer from associated aggregation-caused quenching (ACQ) and high cytotoxicity issues. Therefore, there is a huge demand for stand-alone luminescent polymers that can circumvent these drawbacks and can be employed in diverse applications. In view of that, nonconventional luminescent polymers (NLPs) are being developed and studied extensively for their distinctive characteristics and potential applications in wide-ranging areas, and for an in-depth understanding of photophysical processes in science. These polymers do not contain classical chromophores, but often involve isolated benzene rings or only electron-rich moieties (e.g. amine, CO, –OH, ether, imide, and heteroatoms N, O, P, S, etc.). This review article highlights the recent progress in the field of NLPs, including their synthesis, underlying emission mechanisms, and applications in materials and biological sciences. Besides, it is identified to be the foremost review that extensively emphasizes on both the fluorescence and phosphorescence features of NLPs. Finally, some prospects have been suggested for further exploration in this flourishing field of research.

Since temperature is one of the most significant physiological parameters that dictate the cellular status of living organisms, accurate intracellular temperature measurement is crucial and a valuable biomarker for the diagnosis and treatment of diseases. Herein, we introduce the foremost example of a non-conjugated polymer as a next generation fluorescent thermometer which is capable of addressing the key shortcomings including toxicity and thermal-induced fluorescence quenching associated with π–π conjugated system-based thermometers developed so far. We revealed, for the first time, the unique photophysical and aggregation-induced emission (AIE) characteristics of well-known thermoresponsive poly(N-vinylcaprolactam) (PNVCL) devoid of any classical fluorophore entity. PNVCL underwent a coil to globular conformational transition in an aqueous medium and appeared to be fluorescent above its lower critical solution temperature (LCST) near body temperature (38 °C). Eventually, this intriguing aspect enabled higher cellular uptake of PNVCL at the LCST boundary. By virtue of the AIE effect, the thermo-induced aggregation phenomenon has been ingeniously utilized to apply PNVCL as a novel fluorescent thermometer for intracellular temperature determination.

Design and synthesis of pH responsive polymeric materials has become an important subject in academia as well as in industrial field in recent years due to their applications in diverse field including controlled drug delivery, biomedical applications, membrane science, sensors and actuators, oil recovery, colloid stabilization, etc. Efforts have been made to incorporate stimuli‐responsive biomolecules in synthetic polymers to develop pH responsive “smart” non‐biological hybrid macromolecules with high water solubility, enhanced biocompatibility, bio‐mimetic structure and properties. This review is focused on the recent advances in side‐chain amino acid‐based pH responsive polymers synthesis and potential application aspects of these macromolecular architectures in drug and gene delivery, and other fields. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41084.

Here we report the design and synthesis of polymers containing cholic acid pendant groups, a major bile acid synthesized in the liver from cholesterol. Random copolymers derived from 2-(methacryloyloxy)ethyl cholate (MAECA) with polyethylene glycol methyl ether methacrylate (PEGMA) and N,N-dimethylaminoethyl methacrylate (DMAEMA) have been synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. Compositions of co-monomers in the copolymers were determined by ¹H NMR spectroscopy, which were further used to determine reactivity ratios of the monomers using the extended Kelen–Tüdös method at high conversions. Copolymers from MAECA with PEGMA (P(MAECA-co-PEGMA)) series displayed lower critical solution temperatures (LCSTs) up to 23% MAECA content in the copolymer, which was studied by UV-visible spectroscopy. Both thermo- and pH-responsiveness were observed for the P(MAECA-co-DMAEMA) copolymers with an MAECA unit in the copolymer up to 11.8%. The critical aggregation concentration (CAC) of water soluble copolymers was determined by fluorescence spectroscopy. Self-assembly of random copolymers was investigated by ¹H NMR spectroscopy, dynamic light scattering (DLS), atomic force microscopy (AFM) and scanning electron microscopy (SEM), which indicated micellar structures in water from cholic acid based random copolymers. The polymeric aggregates were further explored for their drug encapsulation capabilities in aqueous medium using nile red as a hydrophobic model compound.