Youqian Xu

Oxidation and pH responsive nanoparticles based on ferrocene-modified chitosan oligosaccharide for 5-fluorouracil delivery

Stimuli-responsive nanoparticles based on biodegradable and biocompatible saccharides are potentially superior carriers under different physical conditions. In this study, we present a detailed investigation on the oxidation and pH responses of ferrocene-modified chitosan oligosaccharide (FcCOS) nanoparticles for 5-Fluorouracil (5-FU) Delivery. The dispersion of FcCOS nanoparticles depends strongly on pH change. NaClO, H2O2 and oxygen, as oxidant models, in a weak acid solution displayed varying accelerations as the disassembly progressed. 5-FU, as a drug model, is efficiently uploaded in FcCOS nanoparticle (approximately 238 nm). The in vitro release of 5-FU from FcCOS nanoparticles studies show that the accumulative release increased with the decrease of pH under bubbled N2. Interestingly, the sample under bubbled air has a higher accumulative release up to 59.64% at pH 3.8, compared with samples under bubbled N2 just 49.02%. The results suggested that FcCOS nanoparticles disassembled faster and the release of drug molecules was accelerated because of the synergistic effect of oxidative agent and low pH. Thus, FcCOS can be developed as an effective pH and oxidation dual-responsive carrier to enhance drug efficacy for cancer treatment.

Enhanced Photophosphorylation of a Chloroplast-Entrapping Long-Lived Photoacid

Enhancing solar energy conversion efficiency is very important for developing renewable energy, protecting the environment, and producing agricultural products. Efficient enhancement of photophosphorylation is demonstrated by coupling artificial photoacid generators (PAGs) with chloroplasts. The encapsulation of small molecular long-lived PAGs in the thylakoid lumen is improved greatly by ultrasonication. Under visible-light irradiation, a fast intramolecular photoreaction of the PAG occurs and produces many protons, remarkably enhancing the proton gradient in situ. Consequently, compared to pure chloroplasts, the assembled natural-artificial hybrid demonstrates approximately 3.9 times greater adenosine triphosphate (ATP) production. This work will provide new opportunities for constructing enhanced solar energy conversion systems.

A self-healing and multi-responsive hydrogel based on biodegradable ferrocene-modified chitosan

Here, we present a novel and facile method for constructing a self-healing hydrogel capable of responding to multiple external stimuli via the self-assembly of biodegradable ferrocene-modified chitosan (FcCS) in an acid aqueous solution at a low concentration of 10 mg mL−1. The hydrogel can re-adhere between cut surfaces and self-heal to its original shape and property after being cut, demonstrating an excellent self-healing property, which is also quantitatively proved by rheological measurements. The hydrogel also presents stimuli-responses towards pH, redox, and different ions such as Cd2+, Cr3+, Pb2+, and Cu2+. In addition, the encapsulation and controlled release of doxorubicin hydrochloride (DOX·HCl) in buffer solutions with different pH values were successfully carried out, which suggests that the accumulative release of DOX·HCl increases as the pH value decreases. All these results indicate that this hydrogel is a promising functional and biomedical material.

Compartmentalized Assembly of Motor Protein Reconstituted on Protocell Membrane toward Highly Efficient Photophosphorylation

Molecule assembly and functionalization of protocells have achieved a great success. However, the yield efficiency of photophosphorylation in the present cell-like systems is limited. Herein, inspired by natural photobacteria, we construct a protocell membrane reconstituting motor protein for highly efficient light-mediated adenosine triphosphate (ATP) synthesis through a layer-by-layer technique. The assembled membrane, compartmentally integrating photoacid generator, proton conductor, and ATP synthase, possesses excellent transparency, fast proton production, and quick proton transportation. Remarkably, these favorable features permit the formation of a large proton gradient in a confined region to drive ATP synthase to produce ATP with high efficiency (873 ATP s-1). It is the highest among the existing artificial photophosphorylation systems. Such a biomimetic system provides a bioenergy-supplying scenario for early photosynthetic life and holds promise in remotely controlled ATP-consumed biosensors, biocatalysts, and biodevices.

Hierarchical self-assembly of protoporphyrin IX-bridged Janus particles into photoresponsive vesicles

Control over the building blocks in supramolecule by hierarchical self-assembly techniques provides a flexible strategy in nanotechnology and material science. In this study, a protoporphyrin IX (PPIX)-bridged Janus particle, as an amphiphilic building block, is driven by host–guest recognition between di-β-cyclodextrin-modified PPIX (PPIX-2CD) and azobenzene (AZO)-focused hydrophobic/hydrophilic hyperbranched polymers. The supramolecular Janus particles were hierarchically constructed into photoresponsive vesicles, which disassembled under the irradiation of ultraviolet (UV) light because of the trans- to cis-isomerization of the AZO groups. Results show that the PPIX-inserted vesicles exhibited excellent photostability against intense infrared radiation and good singlet oxygen producing ability.

Stimuli-Responsive Dipeptide–Protein Hydrogels through Schiff Base Coassembly

Different from the conventional irreversible covalent conjugations, a simple and efficient dynamic Schiff base covalent assembly is developed to construct the stable and smart dipeptide-protein hydrogels under mild conditions. Diphenylalanine-hemoglobin hydrogel is chosen to investigate the gelation formation process and mechanism. It is found that such assembled dipeptide-protein hydrogels are sensitive to pH variation, and simultaneously the proteins can be released without changing the native secondary structures from the gels. Furthermore, these adaptive hydrogels can encapsulate a series of small molecules, multicomponent proteins, and functional nanoparticles. These versatile hydrogels may find a great potential in bioapplications.

Optically Matched Semiconductor Quantum Dots Improve Photophosphorylation Performed by Chloroplasts

A natural-artificial hybrid system was constructed to enhance photophosphorylation. The system comprises chloroplasts modified with optically matched quantum dots (chloroplast-QD) with a large Stokes shift. The QDs possess a unique optical property and transform ultraviolet light into available and highly effective red light for use by chloroplasts. This favorable feature enables photosystem II contained within the hybrid system to split more water and produce more protons than chloroplasts would otherwise do on their own. Consequently, a larger proton gradient is generated and photophosphorylation is improved. At optimal efficiency activity increased by up to 2.3 times compared to pristine chloroplasts. Importantly, the degree of overlap between emission of the QDs and absorption of chloroplasts exerts a strong influence on the photophosphorylation efficiency. The chloroplast-QD hybrid presents an efficient solar energy conversion route, which involves a rational combination of a natural system and an artificial light-harvesting nanomaterial.

Supramolecular Assembly of Photosystem II and Adenosine Triphosphate Synthase in Artificially Designed Honeycomb Multilayers for Photophosphorylation

Plant thylakoids have a typical stacking structure, which is the site of photosynthesis, including light-harvesting, water-splitting, and adenosine triphosphate (ATP) production. This stacking structure plays a key role in exchange of substances with extremely high efficiency and minimum energy consumption through photosynthesis. Herein we report an artificially designed honeycomb multilayer for photophosphorylation. To mimic the natural thylakoid stacking structure, the multilayered photosystem II (PSII)-ATP synthase-liposome system is fabricated via layer-by-layer (LbL) assembly, allowing the three-dimensional distributions of PSII and ATP synthase. Under light illumination, PSII splits water into protons and generates a proton gradient for ATP synthase to produce ATP. Moreover, it is found that the ATP production is extremely associated with the numbers of PSII layers. With such a multilayer structure assembled via LbL, one can better understand the mechanism of PSII and ATP synthase integrated in one system, mimicking the photosynthetic grana structure. On the other hand, such an assembled system can be considered to improve the photophosphorylation.