All-Aqueous-Processed Injectable In Situ Forming Macroporous Silk Gel Scaffolds for Minimally Invasive Intracranial and Osteological Therapies

Hydrogels are widely utilized in regenerative medicine for drug delivery and tissue repair due to their superior biocompatibility and high similarity to the extracellular matrix. For minimally invasive therapies, in situ forming gel scaffolds are desirable, but technical challenges remain to be overcome to achieve the balance between tissue-like strength and cell-sized porosity, especially for intracranial and osteological therapies. Here, a new method-inspired by the liquid crystalline spinning process in natural silk fibers-is reported for preparing injectable silk gel scaffolds with favorable preclinical efficacy and unique characteristics including 1) in situ gelling for minimally invasive surgeries, 2) controllable porosity for efficient cellular infiltration and desirable degradation, 3) resilient and tunable mechanical properties that are compatible with the modulus regime of native soft tissues, and 4) all-aqueous processing that avoids toxic solvents and enables facile loading of bioactive agents. Moreover, hierarchically structured heterogeneous silk gel scaffolds with variable porosity and bioactive agent gradients within 3D matrices can be achieved for sustained drug release and guided tissue regeneration. Preclinical efficacy studies in rodent models show efficient bacterium and glioma inhibition and positive effects on bone regeneration and vascularization.

Antibacterial-nanocomposite bone filler based on silver nanoparticles and polysaccharides

Injectable bone fillers represent an attractive strategy for the treatment of bone defects. These injectable materials should be biocompatible, capable of supporting cell growth and possibly able to exert antibacterial effects. In this work, nanocomposite microbeads based on alginate, chitlac, hydroxyapatite and silver nanoparticles were prepared and characterized. The dried microbeads displayed a rapid swelling in contact with simulated body fluid and maintained their integrity for more than 30 days. The evaluation of silver leakage from the microbeads showed that the antibacterial metal is slowly released in saline solution, with less than 6% of silver released after 1 week. Antibacterial tests proved that the microbeads displayed bactericidal effects toward Staphylococcus aureus, Pseudomonas aeruginosa and Staphylococcus epidermidis, and were also able to damage pre-formed bacterial biofilms. On the other hand, the microbeads did not exert any cytotoxic effect towards osteoblast-like cells. After characterization of the microbeads bioactivity, a possible means to embed them in a fluid medium was explored in order to obtain an injectable paste. Upon suspension of the particles in alginate solution or alginate/hyaluronic acid mixtures, a homogenous and time-stable paste was obtained. Mechanical tests enabled to quantify the extrusion forces from surgical syringes, pointing out the proper injectability of the material. This novel antibacterial bone filler appears as a promising material for the treatment of bone defects, in particular when possible infections could compromise the bone-healing process. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of the oxygen affected layer in multilayered photopolymers

Photopolymerization is known to be limited in depth by light absorption.

B(12)-mediated, long wavelength photopolymerization of hydrogels

Medical hydrogel applications have expanded rapidly over the past decade. Implantation in patients by noninvasive injection is preferred, but this requires hydrogel solidification from a low viscosity solution to occur in vivo via an applied stimuli. Transdermal photo-cross-linking of acrylated biopolymers with photoinitiators and lights offers a mild, spatiotemporally controlled solidification trigger. However, the current short wavelength initiators limit curing depth and efficacy because they do not absorb within the optical window of tissue (600-900 nm). As a solution to the current wavelength limitations, we report the development of a red light responsive initiator capable of polymerizing a range of acrylated monomers. Photoactivation occurs within a range of skin type models containing high biochromophore concentrations.

High strength biocompatible PEG single-network hydrogels

A single-chain PEG hydrogel with extremely high strength was prepared via precise design and control over the molecular topology of the polymeric network.