Preparation of pH-responsive polyurethane nano micelles and their antibacterial application.

Considering the differences in pH between bacterial infection microenvironment and normal tissues, a series of pH-responsive drug-release amphiphilic polyurethane copolymers (DPU-g-PEG) have been prepared in this work. Fourier transform infrared (FT-IR) spectroscopy and 1H NMR was selected to detect the structure of the condensed polymers. The DPU-g-PEG amphiphilic copolymers could form stable micelles with a hydrophilic shell of polyethylene glycol (PEG) and a hydrophobic core of polylactic acid (PLA). We loaded a model drug called triclosan onto DPU-g-PEG micelles and studied how pH affects their particle size, Zeta potential, and drug release performance. The results revealed that when exposed to acidic conditions, the surface potential of DPU-g-PEG micelles changed, the micelles' particle size increased, and the drug release performance was significantly enhanced. These results suggested that the micelles prepared in this study can release more antibacterial substances at sites of bacterial infection. Meanwhile, we also investigated the impact of different ratios of soft and hard segments on the properties of micelles, and the results showed that the pH responsiveness of micelles was strongest when the ratio of soft segments (PLLA diol + PEG 2000): 1,6-hexamethylene diisocyanate (HDI): 2,6-Bis-(2-hydroxy-ethyl)-pyrrolo[3,4-f]isoindole-1,3,5,7-tetraone (DMA) = 1: 1.2: 0.2. Furthermore, the results of inhibition zone test, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) all confirmed the antibacterial activity of triclosan-load DPU-g-PEG micelles. In conclusion, the DPU-g-PEG micelles produced in this study have the potential to be used as intelligent drug delivery systems in the biomedical field.

Fast Response, High Spectral Rejection Ratio, Self-Filtered Ultranarrowband Photodetectors Based on Perovskite Single-Crystal Heterojunctions.

Narrowband photodetectors have wide application potential in high-resolution imaging and encrypted communication, due to their high-precision spectral resolution capability. In this work, we report a fast response, high spectral rejection ratio, and self-filtered ultranarrowband photodetector with a new mechanism, which introduces bulk recombination by doping Bi3+ and cooperates with surface recombination for further quenching photogenerated charges generated by short-wavelength-light excitation in perovskite single-crystal. A perovskite film focused on collecting charges is fabricated on the single crystal by a lattice-matched solution-processed epitaxial growth method. Due to the formation of PN heterojunctions, a narrowband photodetector in this mechanism has remarkable spectral selectivity and detection performance with an ultranarrow full width at half-maximum (FWHM) of 7.7 nm and a high spectral rejection ratio of 790, as well as a high specific detectivity up to 1.5 × 1010 Jones, a fast response speed with a rise time and fall time of ∼8 and 137 µs. The ultrafast and ultranarrow spectra response of self-filtered narrowband photodetector provides a new strategy in high-precision and high-resolution photoelectric detection.

[Empirical study of the transportation of pulmonary surfactant-super oxide dismutase liposome to lung tissue in rats].

OBJECTIVE: To study the feasibility of the transportation of pulmonary surfactant-super oxide dismutase (PS-SOD) liposome to lung tissue in rats. METHODS: 32 Wistar rats were randomly divided into 4 groups (8 rats in each group): normal saline group, PS group, SOD group, PS-SOD liposome group. Each group was further divided into two groups (4 rats in each group), and the rats were respectively killed 2 and 24 hours after the operation. While the biological activity of SOD in irrigating solution and tissue homogenate were detected, lung tissue were labeled with fluorescent and then observed under microscope and transmission electron microscope. RESULTS: PS-SOD liposome was corps rounds with monolayer lipid with stable surface tension and antioxidative activity. At the point of 2 hours after operation, while the SOD biological activity of irrigating solution in PS-SOD liposome group (32.87 +/- 5.47) and SOD group (33.14 +/- 5.61) were obviously higher than that in normal saline group (2.15 +/- 0.17, P < 0.01), there was no difference between them (P > 0.05). The mean fluorescence optical density in PS-SOD liposome group (0.109 +/- 0.018) was lower than that in normal saline group (0.144 +/- 0.052) and PS group (0.143 +/- 0.026, P < 0.01). 24 hours after operation, the SOD biological activity of irrigating solution in PS-SOD liposome group (11.54 +/- 1.42) was the highest (P < 0.01) and the mean fluorescence optical density in PS-SOD liposome group (0.112 +/- 0.018) was the lowest (P < 0.01). The SOD biological activity of tissue homogenate in PS-SOD liposome group (2 h: 16.83 +/- 2.69, 24 h: 15.70 +/- 2.75) was higher than that in normal saline group (2 h: 5.79 +/- 0.93, 24 h: 5.84 +/- 1.31) and in SOD group (2 h: 7.07 +/- 1.04, 24 h: 6.11 +/- 1.06, P < 0.01) both at the point of 2 and 24 hours after the operation. Lots of PS-SOD liposome was observed in type II alveolar epithelial cells under transmission electron microscope. CONCLUSION: Intrathecal administ ration of PS-SOD liposome enhanced the transportation of SOD into lung tissue and its antioxidative activity.