The role and mechanism of tight junctions in the regulation of salivary gland secretion.

Tight junctions (TJs) are cell-cell interactions that localize at the most apical portion of epithelial/endothelial cells. One of the predominant functions of TJs is to regulate material transport through paracellular pathway, which serves as a selective barrier. In recent years, the expression and function of TJs in salivary glands has attracted great interest. The characteristics of multiple salivary gland TJ proteins have been identified. During salivation, the activation of muscarinic acetylcholine receptor and transient receptor potential vanilloid subtype 1, as well as other stimuli, promote the opening of acinar TJs by inducing internalization of TJs, thereby contributing to increased paracellular permeability. Besides, endothelial TJs are also redistributed with leakage of blood vessels in cholinergic-stimulated submandibular glands. Furthermore, under pathological conditions, such as Sjögren's syndrome, diabetes mellitus, immunoglobulin G4-related sialadenitis, and autotransplantation, the integrity and barrier function of TJ complex are impaired and may contribute to hyposalivation. Moreover, in submandibular glands of Sjögren's syndrome mouse model and patients, the endothelial barrier is disrupted and involved in hyposecretion and lymphocytic infiltration. These findings enrich our understanding of the secretory mechanisms that link the importance of epithelial and endothelial TJ functions to salivation under both physiological and pathophysiological conditions.

pH-responsive controlled-release system based on mesoporous bioglass materials capped with mineralized hydroxyapatite.

A controlled release system with pH-responsive ability has been presented. Mesoporous bioglass (MBG) was used as the drug carrier and a spontaneous mineralization method was adopted to cap the pores of the carrier with hydroxyapatite (HAp) and to restrict the drug release. It is a simple and green method to realize the ingenious pH-sensitive controlled release. The model drug, metformin hydrochloride (MH), was loaded simultaneously with the mineralization process. Due to the degradation of HAp at acid environments, the system shows well pH-sensitive drug release ability. The release kinetics can be easily adjusted by the mineralization time and the ion concentration of media. The system is recommended as a promising candidate as a pH-sensitive vehicle for drug controlled release to low pH tissues, such as inflammatory sites and tumors.

Hierarchical porous bioactive glasses/PLGA-magnetic SBA-15 for dual-drug release.

The hierarchical porous bioglass combined with magnetic SBA-15 was synthesized. The bioactive glass materials possess a hierarchical porous structure with the macroporous (50µm) and the mesoporous (3.86nm) structures derived from the plant template (cattail stem) and triblock polyethylene oxide-propylene oxide block copolymer (P123), respectively. Magnetic SBA-15 was synthesized by adopting the post assembly method using Fe(NO3)3 as iron source and ethylene glycol as reduction. After coating PLGA, PLGA-IBU-magnetic SBA-15 also possessed super-paramagnetism and the corresponding saturation magnetizations (Ms) could reach 2.6emug(-1). Metformin HCl (MH) and ibuprofen (IBU) were used as model drugs, and the drug release kinetics was studied. MH and IBU could release 60% and 85% from the sample respectively. The system shows excellent dual-drug controlled delivery performance and good bioactivity in vitro that leads to good potential application on bone regeneration.

Synthesis of hierarchical porous bioactive glasses for bone tissue regeneration.

A novel hierarchical porous bioactive glasses were synthesised with cattail stem and triblock polyethylene oxide-propylene oxide block copolymer (P123) as macroporous template and mesoporous template, respectively. The structural and textural properties of materials were characterised by X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, nitrogen adsorption-desorption, energy dispersive spectrometer and vibrating sample magnetometer technique. The results reveal the bioglasses possess multilevel porous structure with the macroporous size about 50 µm and the mesopore with the diameter of 3.86 nm. Furthermore, metformin HCl was used as the model drug. The drug release kinetics and hydroxyapatite (HAP, (Ca10(PO4)6(OH)2)) inducing-growth ability of the composites were studied, respectively. The system exhibits the fast HAP inducing-growth ability and long-term drug delivery, making them a good candidate for bone tissue regeneration.