Supramolecular systems for bioapplications:recent research progress in China

Supramolecular systems feature dynamic,reversible and stimuli-responsive characteristics,which are not easily achieved by molecular entities.The last decade has witnessed tremendous advances in the investigations of supramolecular systems for various bioapplications,which include drug delivery,anticancer therapy,antibacterial therapy,photodynamic therapy,photothermal therapy,combination therapy,antidotes for residual drugs or toxins,and bioimaging and biosensing.Host-guest chemistry has played a key role in the development of such bioactive supramolecular systems,and natural macrocycles(such as cyclodextrins),synthetic macrocycles(such as calixarenes,cucurbit[n]urils,and pillararenes),and porous framework polymers(such as supramolecular organic frameworks and flexible organic frameworks)have been most successfully used as hosts to build different kinds of host-guest systems for attaining designed biofunctions.The self-assembly of rationally designed amphiphilic molecules,macromolecules and polymers represent another important approach for the construction of supramolecular architectures with advanced biofunctions.In this review,we summarize the important contributions made by Chinese researchers in this field,with emphasis on those reported in the past five years.

J-aggregation of photosensitizers leads to an ultrahigh drug-loading system for targeted delivery

Drug loading capacity is very important in the construction of targeted drug delivery systems(TDDSs)for the improvement of drug delivery efficiency.However,the drug-loading capacity of most nanomaterials is non-idealistic,and developing the high drug-loading TDDSs is still a critical challenge.In this work,an ultrahigh loading system(denoted as HMPB_(2))was prepared via J-aggregation of an aza-boron dipyrromethene derivative(Bod)by using hollow MnO_(2)modified with glucosamine pillar[5]arene as a carrier,which was demonstrated to have typical J-aggregate absorption of Bod,specific cancer cells targeting ability,negligible dark cytotoxicity,and potent phototoxicity.This work provides a successful example to construct an ultrahigh drug-loading system via J-aggregation for targeted delivery.

pH- and H_(2)O_(2)-sensitive drug delivery system based on sodium xanthate:Dual-responsive supramolecular vesicles from one functional group

Nano-drug delivery systems with multiple stimulus-responsive capabilities have superior response performance and efficient drug release.Nevertheless,it is sophisticated to construct multiple stimulus-responsive systems where the two or more functional groups need to be introduced simultaneously.Xanthate,one functional group with pH and H2O2 stimulus responsiveness,has significant potential applications for building dual-responsive drug delivery system.Herein,we present a novel dual stimuli-responsive supramolecular drug delivery system by using sodium xanthate derivative(SXD)as guest molecule and quaternary ammonium capped pillar[5]arene(QAP5)as host molecule through host-guest interaction on the basis of electrostatic interaction.The amphiphile QAP5⊃SXD could self-assemble into vesicles to efficiently load the anti-cancer drug DOX.The experimental results showed that QAP5⊃SXD nanoparticles could achieve efficient drug delivery and controlled release in the tumor microenvironment.Cytotoxicity experiments proved that DOX@QAP5⊃SXD nanoparticles could significantly improve the anticancer efficiency of free DOX on cancer cells.The present study provides an efficient strategy to develop supramolecular nanocarriers with dual-responsiveness in one functional group for controlled drug release.

Design, Analysis and Experimental Performance of a Bionic Piezoelectric Rotary Actuator

This study presents a piezoelectric rotary actuator which is equipped with a bionic driving mechanism imitating the cen- tipede foot. The configuration and the operational principle are introduced in detail. The movement model is established to analyze the motion of the actuator. We establish a set of experimental system and corresponding experiments are conducted to evaluate the characteristics of the prototype. The results indicate that the prototype can be operated stably step by step and all steps have high reproducibility. The driving resolutions in forward and backward motions are 2.31 grad and 1.83 μrad, respectively. The prototype can also output a relatively accurate circular motion and the maximum output torques in forward and backward directions are 76.4 Nmm and 70.6 Nmm, respectively. Under driving frequency of 1 Hz, the maximum angular velocities in forward and backward directions are 1029.3 grad·s^-1 and 1165 μrad·s^-1 when the driving voltage is 120 V. Under driving voltage of 60 V, the angular velocities in forward and backward motions can be up to 235100 grad·s^-1 and 153650 μrad·s^-1 when the driving frequency is 1024 Hz. We can obtain the satisfactory angular velocity by choosing a proper driving voltage and frequency for the actuator.

Facile fabrication of branched-chain carbohydrate chips for studying carbohydrate-protein interactions by QCM biosensor

A novel approach for fabricating branched-chain （BC） carbohydrate chips to study carbohydrate-protein interactions using Quartz Crystal Microbalance （QCM） biosensor was developed. This approach utilizes functional alkynyl-branch molecule modified chip surfaces, which through the terminal alkynyl group for covalent linking of unprotected azide-carbohydrates. The unprotected azide-carbohydrates were syhthesized in one-step using 2-azido-l,B-dimethylqmidazolinium as catalyst, avoiding complex chemical modifications. Additionally, the branch surface modified with the carbohydrates not only supplies more specific binding site but also reveals significant cluster effect. To exemplify the sugar cluster effect on BC carbohydrate chips, BC Galactose and Mannose chips prepared in this work were used to determine carbohydrate-lectin interactions using QCM biosensor. The results clearly showed that BC chip significantly improves the detection sensitivity compared with the straight-chain （SC） chip. More importantly, the BC galactose chip sensitivity was enhanced 40% compared with the SC galactose chip.

Virtual special issue:Supramolecular/macrocyclic chemistry

Welcome to this virtual special issue, which focuses on supramolecular/macrocyclic Chemistry. The beginnings of supramolecular chemistry can be traced back to 1967 with the identification of crown ethers by Pedersen [1], and being acknowledgement by the 1987 Nobel Prize to Lehn, Cram, and Pedersen for their leading discoveries in the host-guest systems [2]. Since these