Gelatinase-responsive photonic crystal membrane for pathogenic bacteria detection and application in vitro health diagnosis.

Selective identification and rapid detection for multiple pathogenic bacteria are important to prevent bacterial infection. Herein, gelatinase-responsive photonic crystal membrane (PCM) is reported as rapid, selective and direct detection platform for multiple pathogenic bacteria. PCMs exhibit angle-independent structural color, and reflection spectra has negligible change after irradiation and storage under different temperature. The ultra-thin response layer makes shorter detection time (30 min) than the reported gelatin-based photonic crystal detection platform (10-12 h). There is obvious positive correlation between reflection spectra change and gelatinase concentration, even if the gelatinase was as low as 4.8 pM. PCM has high stability against multiple interferers, which are beneficial to improve the detection accuracy and reliability. PCM also show "selective" ability to identify typical pathogens from atypical pathogens through specific response to gelatinase, and good selectivity gives PCM direct detection ability without pretreatment. PCM could detect the pathogens bacteria concentration range spanning 7 orders of magnitude from 10 to 107 CFU/mL, and the relative error between gold standard method and the new platform is less than 10%. Furthermore, PCM's in vitro health diagnosis ability was proved by detecting pathogenic bacteria in artificial wound fluid and urine. All the results show that PCM is well promising platform for selective identifying and rapid detecting pathogenic bacteria in vitro diagnosis.

Nanofiber-reinforced bulk hydrogel: preparation and structural, mechanical, and biological properties.

Alginate-based hydrogels are increasingly being used as biomaterials for tissue engineering, drug carriers, and wound dressing; however, their poor mechanical strength limits their applications. Nanofiber reinforcement is an effective method for increasing the mechanical strength of hydrogels. However, the macro preparation of nanofiber-reinforced hydrogels with a bulk structure is challenging. Herein, we describe the fabrication of nanofiber-reinforced bulk alginate hydrogel composites. The mechanical properties of hydrogels were significantly improved, and the reinforcement law of nanofiber was systematically studied. The maximum tensile stress (0.76 MPa) was obtained with 30% nanofiber content, which was 87% higher than that of pure alginate hydrogel. The compressive stress of the composite hydrogel exhibited "J-curve" behavior with gradually increasing nanofiber content, which indicated that the composited hydrogels were suitable as biomaterials. Furthermore, in 2 h, the hydrogels killed more than 90% of the bacteria that were present, and the bacteriostatic rate reached 100% after 12 h of treatment. More importantly, the sterile environment continued to be maintained, and the composited hydrogel also had satisfactory cytocompatibility and cell adhesion. Compared with pure alginate hydrogel, the roughness of the composited hydrogel surface was increased, which resulted in stronger cell adhesion. Therefore, the composite hydrogel demonstrated improved mechanical and biological properties, and exhibited the potential for clinical application.

Surface Functional Nanofiber Membrane for Ultrasensitive and Naked-Eye Visualization of Bacterial Concentration.

Bacterial contamination in water is a serious health risk to human beings, so it is very important to realize the point-of-care (POC) bacterial detection in water. However, the traditional bacterial detection methods are time-consuming, professional- and equipment-dependent, and do not meet the needs of POC detection. There is a pressing need to develop a platform for POC bacterial detection to defeat the increasing risk of bacterial infections. Herein, a surface functional nanofiber membrane (NFM) is prepared by layer-by-layer (LBL) self-assembly as a platform for POC detection of bacterial concentration; it is naked-eye visualization and ultrasensitive. The platform shows obvious bacterial responsiveness, which allows naked-eye visualization of bacterial concentration (102-106 CFU/mL) within 30 min and can quantitatively detect the bacterial concentration (101-106 CFU/mL) by fluorescence within 5 min. The platform not only exhibits high efficiency but also has a low threshold for bacterial concentration detection. Furthermore, the platform shows good consistency with traditional methods in the detection of bacteria in practical water samples, and has the potential for use in detecting bacterial concentrations in water supplies to protect human beings from health hazards. This work also provides useful reference for research on bacterial detection, taking advantage of the surface characteristics of bacteria and the high sensitivity of NFM.