Toxin-Enabled "On-Demand" Liposomes for Enhanced Phototherapy to Treat and Protect against Methicillin-Resistant Staphylococcus aureus Infection.

An effective therapeutic strategy against methicillin-resistant Staphylococcus aureus (MRSA) that does not promote further drug resistance is highly desirable. While phototherapies have demonstrated considerable promise, their application toward bacterial infections can be limited by negative off-target effects to healthy cells. Here, a smart targeted nanoformulation consisting of a liquid perfluorocarbon core stabilized by a lipid membrane coating is developed. Using vancomycin as a targeting agent, the platform is capable of specifically delivering an encapsulated photosensitizer along with oxygen to sites of MRSA infection, where high concentrations of pore-forming toxins trigger on-demand payload release. Upon subsequent near-infrared irradiation, local increases in temperature and reactive oxygen species effectively kill the bacteria. Additionally, the secreted toxins that are captured by the nanoformulation can be processed by resident immune cells to promote multiantigenic immunity that protects against secondary MRSA infections. Overall, the reported approach for the on-demand release of phototherapeutic agents into sites of infection could be applied against a wide range of high-priority pathogens.

Bioglass could increase cell membrane fluidity with ion products to develop its bioactivity.

OBJECTIVES: Silicate bioactive glass (BG) has been widely demonstrated to stimulate both of the hard and soft tissue regeneration, in which ion products released from BG play important roles. However, the mechanism by which ion products act on cells on cells is unclear. MATERIALS AND METHODS: Human umbilical vein endothelial cells and human bone marrow stromal cells were used in this study. Fluorescence recovery after photobleaching and generalized polarization was used to characterize changes in cell membrane fluidity. Migration, differentiation and apoptosis experiments were carried out. RNA and protein chip were detected. The signal cascade is simulated to evaluate the effect of increased cell membrane fluidity on signal transduction. RESULTS: We have demonstrated that ion products released from BG could effectively enhance cell membrane fluidity in a direct and physical way, and Si ions may play a major role. Bioactivities of BG ion products on cells, such as migration and differentiation, were regulated by membrane fluidity. Furthermore, we have proved that BG ion products could promote apoptosis of injured cells based on our conclusion that BG ion products increased membrane fluidity. CONCLUSIONS: This study proved that BG ion products could develop its bioactivity on cells by directly enhancing cell membrane fluidity and subsequently affected cell behaviours, which may provide an explanation for the general bioactivities of silicate material.

Novel double-layer Silastic testicular prosthesis with controlled release of testosterone in vitro, and its effects on castrated rats.

Testicular prostheses have been used to deal with anorchia for nearly 80 years. Here, we evaluated a novel testicular prosthesis that can controllably release hormones to maintain physiological levels of testosterone in vivo for a long time. Silastic testicular prostheses with controlled release of testosterone (STPT) with different dosages of testosterone undecanoate (TU) were prepared and implanted into castrated Sprague-Dawley rats. TU oil was applied by oral administration to a separate group of castrated rats. Castrated untreated and sham-operated groups were used as controls. Serum samples from every group were collected to measure the levels of testosterone (T), follicle-stimulating hormone and luteinizing hormone (LH). Maximum intracavernous penile pressure (ICPmax) was recorded. The prostates and seminal vesicles were weighed and subjected to histology, and a terminal dexynucleotidyl transferase-mediated UTP nick end labeling (TUNEL) assay was used to evaluate apoptosis. Our results revealed that the weights of these tissues and the levels of T and LH showed significant statistical differences in the oral administration and TU replacement groups compared with the castrated group (P < 0.05). Compared with the sham-operated group, the ICPmax, histology and TUNEL staining for apoptosis, showed no significant differences in the hormone replacement groups implanted with medium and high doses of STPT. Our results suggested that this new STPT could release TU stably through its double semi-permeable membranes with excellent biocompatibility. The study provides a new approach for testosterone replacement therapy.

A mesoporous silica nanoparticle--PEI--fusogenic peptide system for siRNA delivery in cancer therapy.

RNA interference (RNAi) is widely regarded as a promising technology for disease treatment, yet one major obstacle for its clinical application is the lack of efficient siRNA delivery vehicles. In this study, we described a magnetic mesoporous silica nanoparticles (M-MSNs)-based, polyelectrolyte (polyethylenimine, PEI) and fusogenic peptide (KALA)-functionalized siRNA delivery system (denoted as M-MSN_siRNA@PEI-KALA), which was highly effective for initiating target gene silencing both in vitro and in vivo. The construction of this delivery system began with the encapsulation of siRNA within the mesopores of M-MSNs, followed by the coating of PEI on the external surface of siRNA-loaded M-MSNs and the chemical conjugation of KALA peptides. The as-prepared delivery vehicles, with notable siRNA protective effect and negligible cytotoxicity, could be easily internalized into cells, readily escape from the endolysosomes and release the loaded siRNA into the cytoplasm. As a result, the knockdown of enhanced green fluorescent protein (EGFP) and vascular endothelial growth factor (VEGF) in tumor cells were observed, both with excellent RNAi efficiencies. In the following in vivo experiments, the intratumoral injection of M-MSN_VEGF siRNA@PEI-KALA significantly inhibited the tumor growth, possibly by the suppression of neovascularization in tumors. To sum up, we have established a highly effective MSNs-based delivery system, which has great potential to serve as therapeutic siRNA formulation for cancer treatment.

The packaging of siRNA within the mesoporous structure of silica nanoparticles.

Mesoporous silica nanoparticle (MSN) is a promising material for biomedical applications, such as delivering drugs or biological molecules (siRNA or DNA), to the target cells or tissues. With positive-charge functionalization on their surface, MSNs have already been used as vectors for siRNA delivery. Nevertheless, such siRNA packaging strategy avoids utilizing the mesopores and consequently hinders further modifications on the delivery vehicle surface. To solve these problems, we have successfully packaged siRNA into the mesopores of magnetic mesoporous silica nanoparticles (M-MSNs) under a strongly dehydrated solution condition. The siRNA-loaded M-MSNs were mixed with polyethyleneimine (PEI) to form a polymer layer on their external surface. The obtained aggregates were further treated by ultrasonication in acidic solution to prepare well dispersed siRNA delivery vehicles (M-MSN_siRNA@PEI). Such delivery vehicles, with effective siRNA protective effect and negligible cytotoxicity, could be internalized into cancer cells and release siRNA in the cytoplasm. In gene silencing experiments, these delivery vehicles mediated, with high efficiency, knockdown of both exogenous enhanced green fluorescent protein (EGFP) gene and endogenous B-cell lymphoma 2 (Bcl-2) gene. In summary, our siRNA packaging strategy extends the application potential of M-MSNs and the resulting siRNA delivery vehicles can be further tested for in vivo experiments.

Insights into the mechanism of magnetofection using MNPs-PEI/pDNA/free PEI magnetofectins.

Magnetofection is an efficient new physical gene transfection technology. Despite its effective gene delivery capability, till now relatively little work has been conducted on the mechanism of magnetofection, especially the intracellular fates of the components of magnetofectins and their effects on magnetofection. In this study, we investigated the mechanism of magnetofection using magnetofectins that were prepared via electrostatic self-assembly of the three components: polyethyleneimine (PEI)-coated magnetic nanoparticles (MNPs-PEI), plasmid DNA (pDNA) and PEI in the free form (free PEI). TEM observation and agarose gel electrophoresis assays have indicated MNPs play the role of driving magnetofectins to the cell surface without entering into the nucleus. Confocal microscopic tracking of fluorescence-labeled PEI has shown that the free PEI (green) can be found in the nucleus but almost all of the MNPs-PEI (red) are confined in the cytoplasm in COS-7 cells 30 min post-transfection or in SPC-A1 cells 90 min post-transfection, implying that the pDNA/PEI complex must separate from MNPs-PEI before entering into the nucleus. In addition, reporter gene assays showed the magnetofectins, in which the free PEI was absent, failed to transfect SPC-A1 or COS-7 cell lines; and there was an optimal ratio of the constituents of magnectofectins to achieve optimal transfection efficiency by balancing stable complex formation and facile release of PEI/pDNA from the complex. In summary, our findings further the knowledge of magnetofection and can be helpful for the design and preparation of gene delivery vehicles for effective magnetofection.