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Currently the standard surgical treatment for bladder defects is augmentation cystoplasty with autologous tissues, which has many side effects. Biomaterials such as small intestine submucosa (SIS) can provide an alternative scaffold for the repair as bladder patches. Previous studies have shown that SIS could enhance the capacity and compliance of the bladder, but its application is hindered by issues like limited smooth muscle regeneration and stone formation since the fast degradation and poor mechanical properties of the SIS. Procyanidins (PC), a natural bio-crosslinking agent, has shown anti-calcification, anti-inflammatory and anti-oxidation properties. More importantly, PC and SIS can crosslink through hydrogen bonds, which may endow the material with enhanced mechanical property and stabilized functionalities. In this study, various concentrations of PC-crosslinked SIS (PC-SIS) were prepared to repair the full-thickness bladder defects, with an aim to reduce complications and enhance bladder functions. In vitro assays showed that the crosslinking has conferred the biomaterial with superior mechanical property and anti-calcification property, ability to promote smooth muscle cell adhesion and upregulate functional genes expression. Using a rabbit model with bladder defects, we demonstrated that the PC-SIS scaffold can rapidly promote in situ tissue regrowth and regeneration, in particular smooth muscle remodeling and improvement of urinary functions. The PC-SIS scaffold has therefore provided a promising material for the reconstruction of a functional bladder.

The use of various types of calcium phosphate has been reported in the preparation of repairing materials for bone defects. However, the physicochemical and biological properties among them might be vastly different. In this study, we prepared two types of calcium phosphates, nano-hydroxyapatite (nHA) and natural bone ceramic (NBC), into 3D scaffolds by mixing with type I collagen (CoL), resulting in the nHA/CoL and NBC/CoL scaffolds. We then evaluated and compared the physicochemical and biological properties of these two calcium phosphates and their composite scaffold with CoL. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD) and compressive tests were used to, respectively, characterize the morphology, composition, distribution and the effect of nHA and NBC to collagen. Next, we examined the biological properties of the scaffolds using cytotoxicity testing, flow cytometry, immunofluorescence staining, biocompatibility testing, CCK-8 assays and RT-PCR. The results reflected that the Ca2+ released from nHA and NBC could bind chemically with collagen and affect its physicochemical properties, including the infrared absorption spectrum and compression modulus, among others. Furthermore, the two kinds of scaffolds could promote the expression of osteo-relative genes, but showed different gene induction properties. In short, NBC/CoL could promote the expression of early osteogenic genes, while nHA/CoL could upregulate late osteogenic genes. Conclusively, these two composite scaffolds could provide MC3T3-E1 cells with a biomimetic surface for adhesion, proliferation and the formation of mineralized extracellular matrices. Moreover, nHA/CoL and NBC/CoL had different effects on the period and extent of MC3T3-E1 cell mineralization.