Self-assembled polyelectrolyte nanoparticles as fluorophore-free contrast agents for multicolor optical imaging

Accurate detection of enzymatic degradation processes of gelatin-alginate microcapsule by 1H NMR spectroscopy: Probing biodegradation mechanism and kinetics

With an increase in the severity of environmental pollution caused by microbeads, the development of biodegradable microcapsules that can be applied in diverse fields has attracted significant attention. The degradation processes are directly related to biodegradable microcapsule creation with high stability and persistence. In this study, biodegradable microcapsules are synthesized via a complex coacervation approach using gelatin and alginate as the capsule main wall materials; additionally, enzyme-induced decomposition mechanisms are proposed by observing spectral changes in proton nuclear magnetic resonance (¹H NMR) analyses. Additional analytical techniques confirm the chemical structure, morphology, and size distribution of the synthesized capsules; these uniform spherical microcapsules are 20-30 μm in size and possess a smooth surface. In addition to characterization, the microcapsules were exposed to targeted enzymes to investigate enzymatic effects using short-term and long-term degradation kinetics. Close inspection reveals that determination of the degradation rate constant of the major components in the capsule is feasible, and suggests two types of 4-stage degradation mechanisms that are enzyme-specific. These investigations demonstrate that capsule degradation can be explored in detail using ¹H NMR spectroscopy to provide a viable strategy for monitoring degradation properties in the development of new biodegradable polymers.

A fluorescence immunoassay for a rapid detection of Listeria monocytogenes on working surfaces

Listeria monocytogenes is a foodborne pathogen responsible for human listeriosis. The increasing incidence of listeriosis induced governments and food manufacturing enterprises to act to diminish the problem. Several methods for the detection of Listeria monocytogenes in food industries were developed. However, they are time-consuming and require the use of specialized equipment. To reduce the detection time of Listeria monocytogenes in food, in this work we developed a fluorescence sandwich immunoassay based on the use of an innovative chitosan-cellulose nanocrystal (CNC) membrane that improves the antigen capture during bacterial growth. The combined use of CNC film for the capture of p60 protein-specific antigen together with the use of fluorescence detection reduced the time of analysis from 24 to 12 h with a limit of detection (LOD) of the assay of 10² CFU/mL (2 Log). In addition, the use of monoclonal anti-PepD covalently immobilized to a CNC membrane assured a high specificity of the assay. Interestingly, the obtained results show no cross-reactivity with the five most diffused pathogen bacteria strains tested.

Fast DNA Extraction with Polyacrylamide Microspheres for Polymerase Chain Reaction Detection

The fast and cost-effective DNA extraction is critical for all DNA-based detections. Here, we fabricated a new kind of polyacrylamide microsphere (PAMMP) in various sizes with two methods, spot polymerization (large size but low yield) and modified inverse microemulsion polymerization (small size but high yield). The fabricated PAMMPs have strong autofluorescence (fPAMMPs), including both visible fluorescence (VF) and near-infrared fluorescence (NIRF), which can remain very stable in various stringent conditions including strong acid and alkali and high temperature. The fabricated fPAMMPs were also highly positively charged, which could be used to effectively capture various biomolecules such as IRDye 800-labeled streptavidin and DNA. We thus developed a new method for rapid extraction (3-5 min) of DNA from various samples including bacteria, mammalian cells, plant and animal solid tissues, and human blood plasma using fPAMMPs. Moreover, the DNA captured on fPAMMPs (fPAMMP@DNA) could be effectively detected by both normal and quantitative PCR amplifications. Finally, we showed that NaBH₄ treatment removed autofluorescence in fPAMMPs (PAMMPs), which could also be applied to DNA extraction and PCR detection. In conclusion, we here fabricated new kinds of fPAMMPs and PAMMPs, developed a new rapid DNA extraction method, and demonstrated their useful applications in PCR detection.

Optimization of Glutaraldehyde Vapor Treatment for Electrospun Collagen/Silk Tissue Engineering Scaffolds

Freestanding fibrous matrices with proper protein composition and desirable mechanical properties, stability, and biocompatibility are in high demand for tissue engineering. Electrospun (E-spun) collagen-silk composite fibers are promising tissue engineering scaffolds. However, as-spun fibers are mechanically weak and unstable. In this work, we applied glutaraldehyde (GA) vapor treatment to improve the fiber performance, and the effect on the properties of E-spun collagen-silk fibers was studied systematically. GA treatment was found to affect collagen and silk distinctively. Whereas GA chemically links collagen peptides, it induces conformational transitions to enrich β-sheets in silk. The combined effects impose a control of the mechanical properties, stability, and degradability of the composite fibers, which are dependent on the extent of GA treatment. In addition, a mild treatment of the fibers did not diminish cell proliferation and viability. However, overly treated fibers demonstrated reduced cell-matrix adhesion. The understanding of GA treatment effects on collagen, silk, and the composite fibers enables effective control and fine tuning of the fiber properties to warrant their diverse in vitro and in vivo applications.

Autofluorescent gelatin nanoparticles as imaging probes to monitor matrix metalloproteinase metabolism of cancer cells

In this paper, autofluorescent gelatin nanoparticles were synthesized as matrix metalloproteinase (MMP) responsive probes for cancer cell imaging. A modified two-step desolvation method was employed to generate these nanoparticles whose size was controllable and had stable autofluorescence. As glutaraldehyde was introduced as the crosslinking agent, the generation of Schiff base (CN) and double carbon bond (CC) between glutaraldehyde and gelatin endowed these gelatin nanoparticles distinct autofluorescence. Considering MMPs were usually overexpressed on the surface of cancer cells and they had degradation ability toward gelatin, we utilized these nanoparticles as imaging probes to responsively monitor the MMP metabolism of cancer cells according to the luminance change. As fluorescent probes, these nanoparticles had facile synthesis procedure and good biocompatibility, and provided a smart strategy to monitor cancer cell behaviors. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2854-2860, 2016.