Effect of Static Magnetic Field on α-Amylase Activity and Enzymatic Reaction

The effect of magnetic field on a-amylase was studied. Under the experimental conditions, a-amylase solution was treated by 0.15 T, 0.30 T and 0.45 T static magnetic fields for a known period of time, then the activity, kinetic parameters, and the secondary conformation were investigated. The results showed that there was a considerable effect of the magnetic exposure on the α-amylase. The activity was increased by 27%, 34.1%, 37.8% compared with the control. It was also found that both kinetic parameters Km and Vm could be decreased due to the increasing magnetic field, Km decreased from 2.20×10^2 to 0.87×10^2, whereas Vm decreased from 2.0×10^3 g/min to 1.1 ×10^3 g/min. At the same time, there were some irregular changes in a-amylase secondary conformation.

Effect of chirality on conformation and cellular uptake of poly(S-(o-nitrobenzyl)-L,D-cysteine) polypeptides

A series of poly（S-（o-nitrobenzyl）-L,D-cysteine） polypeptides with different chirality was synthesized and their molecular structures,secondary conformations,drug release and biological properties were thoroughly investigated.The chirality of the polypeptides had effect on secondary conformations and the cellular uptake behavior of the related nanoparticles.

Thermo-induced physically crosslinked polypeptide-based block copolymer hydrogels for biomedical applications

Stimuli-responsive synthetic polypeptide-containing block copolymers have received considerable attention in recent years.Especially,unique thermo-induced sol-gel phase transitions were observed for elaborately-designed amphiphilic diblock copolypeptides and a range of poly(ethylene glycol)(PEG)-polypeptide block copolymers.The thermo-induced gelation mechanisms involve the evolution of secondary conformation,enhanced intramolecular interactions,as well as reduced hydration and increased chain entanglement of PEG blocks.The physical parameters,including polymer concentrations,sol-gel transition temperatures and storage moduli,were investigated.The polypeptide hydrogels exhibited good biocompatibility in vitro and in vivo,and displayed biodegradation periods ranging from 1 to 5 weeks.The unique thermo-induced sol-gel phase transitions offer the feasibility of minimal-invasive injection of the precursor aqueous solutions into body,followed by in situ hydrogel formation driven by physiological temperature.These advantages make polypeptide hydrogels interesting candidates for diverse biomedical applications,especially as injectable scaffolds for 3D cell culture and tissue regeneration as well as depots for local drug delivery.This review focuses on recent advances in the design and preparation of injectable,thermo-induced physically crosslinked polypeptide hydrogels.The influence of composition,secondary structure and chirality of polypeptide segments on the physical properties and biodegradation of the hydrogels are emphasized.Moreover,the studies on biomedical applications of the hydrogels are intensively discussed.Finally,the major challenges in the further development of polypeptide hydrogels for practical applications are proposed.

Drug-induced hierarchical self-assembly of poly(amino acid)for efficient intracellular drug delivery

As a potent anticancer drug,gambogic acid(GA)suffers from its poor water solubility and low chemical stability and shows a limited clinical outcome.To address this problem,we report here a simple and effective strategy to immobilize and deliver GA using a reducible diblock poly(amino acid)as a model.The electrostatic interaction between GA and polymer enables a high drug loading content up to 53.6%.Moreover,the drug complexation induces a micelle-to-vesicle transformation,combined with a conformation tra nsition from random coil to a-helix.The hierarchically assembled drug nanocomplexes can serve as a smart carrier for efficient cell internalization and triggered release of multiple drugs under intracellular acidic and reductive conditions,resulting in a synergistic antitumor efficacy in vitro.This work provides a new insight into the drug-carrier interaction and a facile nanoplatform for drug delivery applications.