Design strategies for composite matrix and multifunctional polymeric scaffolds with enhanced bioactivity for bone tissue engineering

Over the past few decades, various bioactive material-based scaffolds were investigated and researchers across the globe are actively involved in establishing a potential state-of-the-art for bone tissue engineering applications, wherein several disciplines like clinical medicine, materials science, and biotechnology are involved. The present review article's main aim is to focus on repairing and restoring bone tissue defects by enhancing the bioactivity of fabricated bone tissue scaffolds and providing a suitable microenvironment for the bone cells to fasten the healing process. It deals with the various surface modification strategies and smart composite materials development that are involved in the treatment of bone tissue defects. Orthopaedic researchers and clinicians constantly focus on developing strategies that can naturally imitate not only the bone tissue architecture but also its functional properties to modulate cellular behaviour to facilitate bridging, callus formation and osteogenesis at critical bone defects. This review summarizes the currently available polymeric composite matrices and the methods to improve their bioactivity for bone tissue regeneration effectively.

Carbene modification and reversible crosslinking of silver nanoparticles for controlled antibacterial activity

Silver nanoparticles (Ag NPs) system capable of exhibiting different particle size at different temperature was developed, which depended on the extent of Diels-Alder (DA) reaction of bismaleimide with furan. Thus, Ag NPs were functionalized on the surface by a furyl-substituted carbene through an insertion reaction. Subsequent reversible DA crosslinking achieved a controlled aggregation with different particle size, which gives a series of different antibacterial activity. These Ag NPs were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), and Nanoparticle Size Analyzer. The aggregation of the Ag NPs could be reliably adjusted by varying the temperature of DA/reverse-DA reaction. The antibacterial activity was assessed using the inhibition zone method against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), which decreased first and then increased in agreement with the size evolution of Ag NPs. This approach opens a new horizon for the carbene chemistry to modify silver nanoparticles with variable size and give controlled antibacterial activity.

Photochromic Materials by Postpolymerisation Surface Modification

Photochromic materials are available by a postpolymerization surface modification of diverse polymers in a multistep sequential process mediated, first, by carbene insertion chemistry, second, by diazonium coupling with a tethered precursor, and finally by coupling to a spiropyran. This three-step sequence is efficient, and surface loading densities of 10¹³ molecules cm^-2 are typically achievable, leading to materials with observable photochromic and wettability behavior, which operate over multiple cycles without significant photobleaching or loss of efficacy. Materials suitable for application in this process include both reactive, but also lower surface energy polymers. Although the process is particularly efficient for high surface area materials, surface modification onto lower surface area substrates, while being intrinsically less efficient, is nonetheless sufficiently effective that changes in macroscopic photochromic properties are readily observable.

Preparation, Post-Modification, and Antibacterial Application of Gelatin Electrospun Membranes

Two bis(diaryldiazomethane)s substituted with amino groups are synthesized and used for the surface modification of membranes electrospun from gelatin. These membranes are then reacted with tolylene-2,4-diisocyanate to give urea-functionalized materials, so that hydrogen peroxide can be reversibly bound onto their surface. These membranes are characterized by scanning electron microscopy, XPS, differential scanning calorimeter, and tensile test to show their surface properties and bulk properties. The surface modification with amino-substituted diazomethanes and the subsequent cross-linking reaction with diisocyanates contribute to high loadings of hydrogen peroxide, and greatly increase the antibacterial activity of gelatin-derived membranes, which open a new horizon in the preparation of high loading antiseptic/antibacterial biomacromolecular surfaces and interfaces.

Electrospun Gelatin Membrane Cross-Linked by a Bis(diarylcarbene) for Oil/Water Separation: A New Strategy To Prepare Porous Organic Polymers

Porous organic polymers (POPs) as absorbing materials have attracted increasing attention. Here, we report a new approach to prepare these polymers for selective oil absorption from oil/water mixtures. Perfluoroalkylbis(diaryldiazomethane) was synthesized and used to modify the surface of an electrospun gelatin membrane by a carbene insertion reaction, not only to immobilize the porous network morphology by cross-linking but also to introduce perfluoroalkyl groups for oil/water separation. The membrane was characterized to show its surface and bulk properties, as well as its performance for absorption capacity, selectivity, and renewability. This approach offers a new horizon in the preparation of POPs for oil/water separation.