One of the leading causes for the failure of dental composite restorations is secondary caries. Effectively inhibiting cariogenic biofilms and reducing secondary caries could extend the service life of composite restorations. Dental composites releasing antibacterial agents such as chlorhexidine (CHX) have shown biofilm-inhibitory efficacy, but they usually have poor physical and mechanical properties. Herein, we present a study of a new method to encapsulate and release CHX from dental composite using mesoporous silica nanoparticles (MSNs). SBA-15 MSNs were synthesized according to a reported procedure. CHX (62.9 wt%) was encapsulated into dried MSN from 0.3 M CHX ethanol solution. The dental composites containing 0% (control), 3%, 5%, and 6.3% CHX or the same amounts of CHX entrapped in MSN (denoted as CHX@MSN) were fabricated with methacrylate monomers and silanized glass fillers (CHX or CHX@MSN + glass filler particle = 70 wt%). The monomer mixture consisted of bisphenol A glycidyl methacrylate (BisGMA), hexanediol dimethacrylate (HDDMA), ethoxylated bisphenol A dimethacrylate (EBPADMA), and urethane dimethacrylates (UEDMA) at a weight ratio of 40:30:20:10. The composites were tested for CHX release and recharge, flexural strength and modulus (at 24 hr and 1 mo), surface roughness, in vitro wear, and antibacterial activity against Streptococcus mutans and Lactobacillus casei (in both planktonic growth and biofilm formation). The results showed that the composites with CHX@MSN largely retained mechanical properties and smooth surfaces and showed controlled release of CHX over a long time. In contrast, the composites with directly mixed CHX showed reduced mechanical properties, rough surfaces, and burst release of CHX in a short time. The composites with CHX either directly mixed or in MSN showed strong inhibition to S. mutans and L. casei. This research has demonstrated the successful application of MSNs as a novel nanotechnology in dental materials to inhibit oral biofilm without sacrificing materials' mechanical properties and surface integrity.

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We consider heterogeneously interacting diffusive particle systems and their large population limit. The interaction is of mean field type with weights characterized by an underlying graphon. A law of large numbers result is established as the system size increases and the underlying graphons converge. The limit is given by a graphon mean field system consisting of independent but heterogeneous nonlinear diffusions whose probability distributions are fully coupled. Well-posedness, continuity and stability of such systems are provided. We also consider a not-so-dense analogue of the finite particle system, obtained by percolation with vanishing rates and suitable scaling of interactions. A law of large numbers result is proved for the convergence of such systems to the corresponding graphon mean field system.

Background Previous studies revealed that urine-derived stem cells (USCs) could promote myogenesis after the impairment of the sphincter muscles. However, the effects of exosomes secreted by USCs (USCs-Exo) were not elucidated. Exosomes are nanosized membrane vesicles secreted by the cells. They have been proved to be effective in protecting against tissue injury and therapeutic in tissue repair. USCs are ideal sources of exosomes because of the noninvasive obtaining method and self-renewal abilitiy. This study aimed to show the therapeutic effects of USCs-Exo on improving stress urinary incontinence (SUI). Methods Rat SUI models were established in this study using vaginal balloon inflation, and urodynamic and histological examination were carried out after exosome application. The proliferation and differentiation of muscle satellite cells (SCs) were evaluated using EdU, Cell Counting Kit 8, immunofluorescence staining, and Western blot analysis. mRNAs and proteins related to the activation of SCs were detected by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis. Results After exosome injection, the urodynamic parameters significantly improved and the injured muscle tissue recovered well. The activation, proliferation, and differentiation of SCs were promoted. The phosphorylation of extracellular-regulated protein kinases (ERK) was enhanced. When ERK was inhibited, the promoting effect of USCs-Exo treatment disappeared. Conclusion The findings of this study elucidated the functional roles of USCs-Exo in satellite cell ERK phosphorylation and identified a novel agent for skeletal muscle regeneration, providing a basis for further exploring a cell-free correction for SUI. Electronic supplementary material The online version of this article (10.1186/s13287-019-1182-4) contains supplementary material, which is available to authorized users.