Biocatalytic Synthesis Using Self-Assembled Polymeric Nano- and Microreactors.

Biocatalysis is increasingly being explored for the sustainable development of green industry. Though enzymes show great industrial potential with their high efficiency, specificity, and selectivity, they suffer from poor usability and stability under abiological conditions. To solve these problems, researchers have fabricated nano- and micro-sized biocatalytic reactors based on the self-assembly of various polymers, leading to highly stable, functional, and reusable biocatalytic systems. This Review highlights recent progress in self-assembled polymeric nano- and microreactors for biocatalytic synthesis, including polymersomes, reverse micelles, polymer emulsions, Pickering emulsions, and static emulsions. We categorize these reactors into monophasic and biphasic systems and discuss their structural characteristics and latest successes with representative examples. We also consider the challenges and potential solutions associated with the future development of this field.

Supramolecular Gel Based on Crown-Ether-Appended Dynamic Covalent Macrocycles.

A new type of dynamic covalent macrocycle with self-promoted supramolecular gelation behavior is developed. Under oxidative conditions, the dithiol compound containing a diamide alkyl linker with an odd number (7) of carbon chain and an appended crown ether shows a remarkable gelation ability in acetonitrile, without any template molecules. Due to the existence of crown ethers and disulfide bonds, the obtained gel shows a multiple stimuli-responsiveness behavior. The mechanical properties and reversibility of the gel are investigated. Computational modeling suggests that the peripheral chain for diamide hydrogen bonding is responsible for the gelation process.

Effect of Low-Frequency Pulsed Ultrasound on Drug Delivery, Antibacterial Efficacy, and Bone Cement Degradation in Vancomycin-Loaded Calcium Phosphate Cement.

BACKGROUND Calcium phosphate cement (CPC) has been applied as a biodegradable antibiotic carrier in osteomyelitis. However, the drug delivery, antibacterial efficacy, and degradation rate of CPC are insufficient and require further improvement in clinical application. MATERIAL AND METHODS Vancomycin-loaded CPC columns were prepared, and eluted in simulated body fluid. The drug delivery was assessed in the ultrasound group and control group by fluorescence polarization immunoassay. The antibacterial efficacy of vancomycin in the ultrasound group and control groups was investigated by standard plate count method. Low-frequency pulsed ultrasound (46.5 kHz, 900 mW/cm²) was used to produce a sinusoidal wave in the ultrasound groups. The percentage of residual weight was evaluated to assess the degradation of CPC. RESULTS The concentration and cumulatively released percentage of vancomycin in the ultrasound group were higher than that in the control group at each time point (p<0.05). The duration of vancomycin concentration over the level of minimum inhibitory concentration was significantly prolonged in the ultrasound group (p<0.05). Antibacterial efficacy of vancomycin in the ultrasound group was significantly greater than that in the control group with same concentration of vancomycin (p<0.05). The percentage of residual weight in the ultrasound group was significantly less than that in the control group (p<0.05). CONCLUSIONS Low-frequency pulsed ultrasound can enhance vancomycin release, prolong the duration of vancomycin concentration at high levels, and accelerate the degradation rate of vancomycin-loaded CPC.

Water-actuated reversible shape-memory polydimethylsiloxane for potential biomedical applications.

Shape memory polymers (SMPs) show great potential in biomedical fields. However, most of the SMPs are not suitable for use in the human body due to their deleteriousness and harsh actuation conditions. It is important to diversify SMPs that could be actuated in the human body environment. Herein, we construct a reversible shape-memory polydimethylsiloxane (RSMPDMS) based on a feasible strategy by deposing the PDMS-salt layer with dynamic micro-creases on the pure PDMS layer. Testing results reveal that it equips with self-expanding, bio-compatibility, drug storage-release and good mechanical toughness. The RSMPDMS could be variously shaped, such as ring, coil, and spiral. The prepared samples present efficient deformation-recovery with high mechanical stability during water absorption-desorption cycles. Moreover, the RSMPDMS is confirmed biocompatible by cell viability analysis and cell fluorescent labeling method, accompanied with efficient drug storage-release. The novel-designed RSMPDMS may contribute to the development of new shape memory biomedical materials.

Low-intensity pulsed ultrasound enhances antibiotic release of gentamicin-loaded, self-setting calcium phosphate cement.

Objective This study aimed to investigate the effect of low-intensity pulsed ultrasound on antibiotic release from gentamicin-loaded, self-setting calcium phosphate cement. Methods A gentamicin-loaded calcium phosphate cement cylinder was eluted in stimulated body fluid. Low-intensity pulsed ultrasound (46.5 kHz, 200 mW/cm2) was used to produce a sinusoidal wave in the experimental group. Non-gentamicin calcium phosphate cement was used in the control group. Results The transient concentration and cumulatively released percentage of gentamicin in the ultrasound group were higher than those in control group at every time point. The duration of gentamicin concentrations over the level of the minimum inhibitory concentration was significantly prolonged in the ultrasound group compared with the control group. Antibacterial efficacy of gentamicin in the ultrasound group was significantly better than that in the control group with the same concentration of gentamicin. Conclusion Low-intensity pulsed ultrasound enhances antibiotic release, providing sustained antibiotic release at high concentrations. This increases the antibacterial effect of gentamicin.