Highly resilient and fatigue-resistant poly(4-methyl-ε-caprolactone) porous scaffold fabricated via thiol-yne photo-crosslinking/salt-templating for soft tissue regeneration.

Elastomeric scaffolds, individually customized to mimic the structural and mechanical properties of natural tissues have been used for tissue regeneration. In this regard, polyester elastic scaffolds with tunable mechanical properties and exceptional biological properties have been reported to provide mechanical support and structural integrity for tissue repair. Herein, poly(4-methyl-ε-caprolactone) (PMCL) was first double-terminated by alkynylation (PMCL-DY) as a liquid precursor at room temperature. Subsequently, three-dimensional porous scaffolds with custom shapes were fabricated from PMCL-DY via thiol-yne photocrosslinking using a practical salt template method. By manipulating the Mn of the precursor, the modulus of compression of the scaffold was easily adjusted. As evidenced by the complete recovery from 90% compression, the rapid recovery rate of >500 mm min-1, the extremely low energy loss coefficient of <0.1, and the superior fatigue resistance, the PMCL20-DY porous scaffold was confirmed to harbor excellent elastic properties. In addition, the high resilience of the scaffold was confirmed to endow it with a minimally invasive application potential. In vitro testing revealed that the 3D porous scaffold was biocompatible with rat bone marrow stromal cells (BMSCs), inducing BMSCs to differentiate into chondrogenic cells. In addition, the elastic porous scaffold demonstrated good regenerative efficiency in a 12-week rabbit cartilage defect model. Thus, the novel polyester scaffold with adaptable mechanical properties may have extensive applications in soft tissue regeneration.

A biodegradable, flexible photonic patch for in vivo phototherapy.

Diagnostic and therapeutic illumination on internal organs and tissues with high controllability and adaptability in terms of spectrum, area, depth, and intensity remains a major challenge. Here, we present a flexible, biodegradable photonic device called iCarP with a micrometer scale air gap between a refractive polyester patch and the embedded removable tapered optical fiber. ICarP combines the advantages of light diffraction by the tapered optical fiber, dual refractions in the air gap, and reflection inside the patch to obtain a bulb-like illumination, guiding light towards target tissue. We show that iCarP achieves large area, high intensity, wide spectrum, continuous or pulsatile, deeply penetrating illumination without puncturing the target tissues and demonstrate that it supports phototherapies with different photosensitizers. We find that the photonic device is compatible with thoracoscopy-based minimally invasive implantation onto beating hearts. These initial results show that iCarP could be a safe, precise and widely applicable device suitable for internal organs and tissue illumination and associated diagnosis and therapy.

In Situ Forming and Reversibly Cross-Linkable Hydrogels Based on Copolypept(o)ides and Polysaccharides.

The emerging tide of hydrogels in biomedical fields drives them to possess good biocompatibility, tunable mechanical properties, and fast gelation process. Herein, a composite hydrogel containing copolypept(o)ides and functional polysaccharides was constructed through dynamic acylhydrazone linkages. First, a series of peptide-peptoid copolymers were synthesized by ring-opening polymerization of sarcosine (Sar) and l-glutamic acid γ-benzyl ester (BLG) N-carboxyanhydrides (NCAs). The benzyl groups of BLG units were substituted with hydrazide groups through ester-amide exchange aminolysis reaction. The statistical copolymer of poly(sarcosine-co-glutamate-hydrazide) (P(Sar-co-GH)) was chosen as an optimized precursor due to its excellent water solubility and gel-forming ability with aldehyde-modified sodium alginate (OSA). Moreover, cellulose nanocrystals (CNCs) were prepared as nanofillers to reinforce the P(Sar-co-GH)-OSA hydrogel. We demonstrated that the copolymer sequences and composition contents made a difference to the properties of the formed hydrogels by variation of the cross-linking density. The dynamic acylhydrazone bonds endowed hydrogels with pH responsiveness and reversible networks. The NIH/3T3 cells encapsulated in the hydrogels maintained high viability and proliferation abilities, indicating that the nanocomposite hydrogels could be explored to fabricate a customized responsive drug delivery system or cell scaffolds for tissue engineering.