Light-Regulated Natural Fluorescence of the PCC 6803@ZIF-8 Composite as an Encoded Microsphere for the Detection of Multiple Biomarkers

Ultrarobust stable ABTS radical cation prepared using Spore@Cu-TMA biocomposites for antioxidant capacity assay

Herein, spore@Cu-trimesic acid (TMA) biocomposites were prepared by self-assembling Cu-based metal-organic framework on the surface of Bacillus velezensis spores. The laccase-like activity of spore@Cu-TMA biocomposites was enhanced by 14.9 times compared with that of pure spores due to the reaction of Cu2+ ions with laccase on the spore surface and the microporous structure of Cu-TMA shell promoting material transport and increasing substrate accessibility. Spore@Cu-TMA rapidly oxidized and transformed 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) into ABTS●+ without using H2O2. Under optimum conditions, the ABTS●+ could be stored for 21 days at 4 °C and 7 days at 37 °C without the addition of any stabilizers, allowing for the large-scale preparation and long-term storage of ABTS●+. The ultrarobust stable ABTS●+ obtained with the use of Cu-TMA could effectively reduce the "back reaction" by preventing the leaching of the metabolites released by the spores. On the basis of these findings, a rapid, low-cost, and eco-friendly colorimetric platform was successfully developed for the detection of antioxidant capacity. Determination of antioxidant capacity for several antioxidants such as caffeic acid, glutathione, and Trolox revealed their corresponding limits of detection at 4.83, 8.89, and 7.39 nM, respectively, with linear ranges of 0.01-130, 0.01-140, and 0.01-180 μM, respectively. This study provides a facile way to prepare ultrarobust stable ABTS●+ and presents a potential application of spore@Cu-TMA biocomposites in food detection and bioanalysis.

Microorganisms@aMIL-125 (Ti): An Amorphous Metal-Organic Framework Induced by Microorganisms and Their Applications

Amorphous metal-organic framework (aMOF)-based materials have attracted considerable attention as an emerging class of nanomaterials. Herein, novel microorganisms@aMIL-125 (Ti) composites including yeast@aMIL-125 (Ti), PCC 6803@aMIL-125 (Ti), and Escherichia coli@aMIL-125 (Ti) composites were respectively synthesized by self-assembling aMOFs on the microorganisms' surface. The functional groups on the microorganisms' surface induced structural defects and participated in the formation of aMIL-125 (Ti) composites. Finally, the application of microorganisms@aMIL-125 (Ti) composites for the removal of glyphosate from aqueous solution was selected as a model reaction to illustrate their potential for environmental protection. The present method is not only economical but also has other advantages including ease of operation, environmentally friendly assay, and high adsorption. The maximum adsorption capacity of aMIL-125 (Ti) was 1096.25 mg g^-1, which was 1.74 times that of crystalline MIL-125 (Ti). Therefore, the microorganisms@aMOFs composites will have broad application prospects in energy storage, drug delivery, catalysis, adsorbing toxic substances, sensing, encapsulating and delivering enzymes, and in other fields.

Biomimetic Assembly of Spore@ZIF-8 Microspheres for Vaccination

Vaccines have been one of the most powerful weapons to defend against infectious diseases for a long time now. Subunit vaccines are of increasing importance because of their safety and effectiveness. In this work, a Bacillus amyloliquefaciens spore@zeolitic imidazolate framework-8 (ZIF-8) vaccine platform is constructed. The ovalbumin (OVA) is encapsulated in the ZIF-8 shells as a model antigen to form a spore@OVA@ZIF-8 (SOZ) composite. The assembly of ZIF-8 improves the loading content of OVA on the spores and provides OVA with long-term protection. The SOZ composite enhances the immunization efficacy in multiple ways, such as facilitation of antigen uptake and lysosome escape, stimulation of dendritic cells to mature and secrete cytokines, boosting of antibody production and formation of an antigen depot. This platform shows several advantages including easy preparation, cost-effectiveness, long life, convenience of transportation and storage, and no need for the cold chain. These findings may have promising implications for the rational design of safe and effective spore-based composite vaccine platforms.