Revisiting PFA-mediated tissue fixation chemistry: FixEL enables trapping of small molecules in the brain to visualize their distribution dynamics

Various small molecules have been used as functional probes for tissue imaging in medical diagnosis and pharmaceutical drugs for disease treatment. The spatial distribution, target selectivity, and diffusion/extrusion kinetics of small molecules in structurally complicated specimens are critical for function. However, robust methods for precisely evaluating these parameters in the brain have been limited. Herein we report a new method termed "Fixation-driven chemical crosslinking of exogenous ligands (FixEL)" which traps and images exogenously administered molecules-of-interest (MOI) in complex tissues. This method relies on proteins-MOI interactions, and chemical crosslinking of amine-tethered MOI with paraformaldehyde used for perfusion fixation. FixEL is used to obtain images of the distribution of the small molecules and their dynamics, which addresses selective/nonselective binding to proteins, time-dependent localization changes, and diffusion/retention kinetics of MOI such as PET tracer derivatives or drug-like small molecules. Clear imaging of a nanobody distributed in the whole brain was also achieved with high spatial resolution using 2D/3D mode.

Optimization of Cellulose-Based Hydrogel Synthesis Using Response Surface Methodology

Synthesis parameters have a significant effect on the properties of cellulose hydrogel. This study aimed to investigate the effects of synthesis parameters, e.g., the cellulose and crosslinkers concentration, on the hydrogels' swelling ratio under both heating and freezing gelation conditions, respectively. Cellulose hydrogels were prepared from wastepaper by the chemical crosslinking method by using epichlorohydrin ECH as a crosslinker. The effects of the synthesis parameters were compared and optimized by response surface methodology (RSM). Synthesized cellulose-based hydrogels under optimized conditions demonstrated an excellent swelling ratio of around 2800%. The optimum swelling ratio of 2467.72% was achieved from the experiment under the heating gelation condition. Thus the synthesized cellulose hydrogels are promising water-saving materials or controlled-release fertilizer carriers for sustainable horticultural and agricultural applications.

Fabrication and Characterization of Ta–GelMA–BG Scaffolds by Chemical Crosslinking Processing for Promotion Osteointegration

The repair of bone defects in load-bearing positions still faces great challenges. Tantalum (Ta) has attempted to repair bone defects based on the excellent mechanical properties. However, the osseointegration of Ta needs to be improved due to the lack of osteoinduction. Herein, tantalum–gelatin–methacryloyl–bioactive glass (Ta–GelMA–BG) scaffolds were successfully fabricated by loading BG in 3D-printed Ta scaffolds through a chemical crosslinking method. The results showed that the composite scaffolds have the ability to promote cell adhesion and proliferation. The incorporation of BG resulted in a significant increase in apatite-forming and osteogenesis differentiation abilities. In vivo results indicated that the Ta–GelMA–BG scaffolds significantly enhanced the osteointegration at the early stage after implantation. Overall, the Ta–GelMA–BG scaffolds are a promising platform for the load bearing bone regeneration field.

Sustainable Cationic Cellulose for Highly Efficient Flocculation of Suspended Particles

Sustainable, cationic cellulose bio-flocculants with various amino group contents were successfully prepared by a feasible chemical crosslinking with polyethyleneimine (PEI). The flocculation performances of diverse PEI-grafting cellulose (CE-PEI)were evaluated topurify sewage sludge treatment. Further, the preparation conditions and flocculation mechanismof CE-PEI were investigated. Benefiting from the high surface positive charges and the supramolecular structure of PEI, the results indicate that CE-PEI could remove the turbid Kaolin suspension effectively. The efficiency of CE-PEI for removing the turbid in Kaolin suspension is 98.2%.Flocculation kinetic results indicated that charge neutralization was the dominant mechanism for the flocculation process. And then, the small Kaolin particles agglomerate together to form large flocs by the function of adsorbing, gathering, and enwrapping. Thus, this work not only exploits a promising application of cellulose as a bio-flocculantbut also provides a feasible approach to efficiently purify high turbidity wastewater.

Crosslinking of Gelatin in Bicomponent Electrospun Fibers

Four chemical crosslinking methods were used in order to prevent gelatin leaching in an aqueous environment, from bicomponent polycaprolactone/gelatin (PCL/Gt) nanofibers electrospun from an alternative solvent system. A range of different concentrations and reaction times were employed to compare genipin, 1-(3-dimethylaminopropyl)-N’-ethylcarbodimide hydrochloride/N-hydroxysuccinimide (EDC/NHS), 1,4-butanediol diglycidyl ether (BDDGE), and transglutaminase. The objective was to optimize and find the most effective method in terms of reaction time and solution concentration, that at the same time provides satisfactory gelatin crosslinking degree and ensures good morphology of the fibers, even after 24 h in aqueous medium in 37 °C. The series of experiments demonstrated that, out of the four compared crosslinking methods, EDC/NHS was able to yield satisfactory results with the lowest concentrations and the shortest reaction times.