One-pot synthetic route to polymer-silica assembled capsule encased with nonionic drug molecule

Preparation, Physicochemical Characterization, Antimicrobial Effects, Biocompatibility and Cytotoxicity of Co-Loaded Meropenem and Vancomycin in Mesoporous Silica Nanoparticles

Mesoporous silica nanoparticles (MSNPs) have been reported as an effective system to co-deliver a variety of different agents to enhance efficiency and improve biocompatibility. This study was aimed at the preparation, physicochemical characterization, antimicrobial effects, biocompatibility, and cytotoxicity of vancomycin and meropenem co-loaded in the mesoporous silica nanoparticles (Van/Mrp-MSNPs). The prepared nanoparticles were explored for their physicochemical features, antibacterial and antibiofilm effects, biocompatibility, and cytotoxicity. The minimum inhibitory concentrations (MICs) of the Van/Mrp-MSNPs (0.12-1 µg/mL) against Staphylococcus aureus isolates were observed to be lower than those of the same concentrations of vancomycin and meropenem. The minimum biofilm inhibitory concentration (MBIC) range of the Van/Mrp-MSNPs was 8-64 μg/mL, which was lower than the meropenem and vancomycin MBICs. The bacterial adherence was not significantly decreased upon exposure to levels lower than the MICs of the MSNPs and Van/Mrp-MSNPs. The viability of NIH/3T3 cells treated with serial concentrations of the MSNPs and Van/Mrp-MSNPs were 73-88% and 74-90%, respectively. The Van/Mrp-MSNPs displayed considerable inhibitory effects against MRSA, favorable biocompatibility, and low cytotoxicity. The Van/Mrp-MSNPs could be a potential system for the treatment of infections.

Antibacterial and biofilm-inhibitory effects of vancomycin-loaded mesoporous silica nanoparticles on methicillin-resistant staphylococcus aureus and gram-negative bacteria

The present study aimed to prepare and characterize vancomycin-loaded mesoporous silica nanoparticles (Van-MSNs) to detect inhibitory effects on the planktonic and biofilm forms of methicillin-resistant Staphylococcus aureus (MRSA) isolates, and study the biocompatibility and toxicity of Van-MSNs in vitro as well as antibacterial activity of Van-MSNs against Gram-negative bacteria. The inhibitory effects of Van-MSNs were investigated on MRSA using the determination of minimum inhibitory (MIC) and minimum biofilm-inhibitory concentrations (MBIC) as well as the effect on bacterial attachment. Biocompatibility was studied by examining the effect of Van-MSNs on the lysis and sedimentation rate of red blood cells (RBC). The interaction of Van-MSNs with human blood plasma was detected by the SDS-PAGE approach. The cytotoxic effect of the Van-MSNs on human bone marrow mesenchymal stem cells (hBM-MSCs) was evaluated by the MTT assay. The antibacterial effects of vancomycin and Van-MSNs on Gram-negative bacteria were also investigated using MIC determination using the broth microdilution method. Furthermore, bacteria outer membrane (OM) permeabilization was determined. Van-MSNs showed inhibitory effects on planktonic and biofilm forms of bacteria on all isolates at levels lower than MICs and MBICs of free vancomycin, but the antibiofilm effect of Van-MSNs was not significant. However, Van-MSNs did not affect bacterial attachment to surfaces. Van-loaded MSNs did not show a considerable effect on the lysis and sedimentation of RBC. A low interaction of Van-MSNs was detected with albumin (66.5 kDa). The hBM-MSCs viability in exposure to different levels of Van-MSNs was 91-100%. MICs of ≥ 128 µg/mL were observed for vancomycin against all Gram-negative bacteria. In contrast, Van-MSNs exhibited modest antibacterial activity inhibiting the tested Gram-negative bacterial strains, at concentrations of ≤ 16 µg/mL. Van-MSNs increased the OM permeability of bacteria that can increase the antimicrobial effect of vancomycin. According to our findings, Van-loaded MSNs have low cytotoxicity, desirable biocompatibility, and antibacterial effects and can be an option for the battle against planktonic MRSA.

Synthesis and Characterization of Polyethylenimine-Silica Nanocomposite Microparticles

A novel procedure for the synthesis of polyethylenimine (PEI)-silica nanocomposite particles with high adsorption capacities has been developed based on an emulsion templating concept. The exceptional chelating properties of PEI as the parent polymer for the particle core promote the binding abilities of the resulting composite for charged species. Further, the subsequent introduction of silica via the self-catalyzed hydrolysis of tetraethoxysilane facilitates production of robust composite particles with smooth surfaces, enabling potential use in multiphase environments. To enable tailored application in solid/liquid porous environments, the production of particles with reduced sizes was attempted by modulating the shear rates and surfactant concentrations during emulsification. The use of high-speed homogenization resulted in a substantial decrease in average particle size, while increasing surfactant loading only had a limited effect. All types of nanocomposites produced demonstrated excellent binding capacities for copper ions as a test solute. The maximum binding capacities of the PEI-silica nanocomposites of 210-250 mg/g are comparable to or exceed those of other copper binding materials, opening up great application potential in resources, chemical processing, and remediation industries.

Silica capsules enclosing P123 triblock copolymer micelles for flurbiprofen storage and release

Flurbiprofen was incorporated in 200-400 nm silica capsules filled with Pluronic P123 polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer. The assembly process of the capsules and the molecular organization of drug molecule, surfactant and silica were investigated using SAXS, TGA, SEM, DLS, DSC, ¹³C single-pulse, CPMAS and ¹H-¹H two-dimensional NMR. Flurbiprofen molecules are molecularly dispersed inside polypropylene cores of P123 surfactant micelles occluded in a 20-30 nm thick silica shell. Flurbiprofen molecules in polypropylene cores of P123 micelles exhibit high mobility and are easily released after introduction in simulated gastrointestinal fluid and the solubility limit is reached within minutes. Release rates are favored at high pH due to acid dissociation of the carboxylic acid group of the flurbiprofen molecule. The molecular environment of flurbiprofen in these P123 filled silica capsules is different from ordered mesoporous silica materials synthesized using P123 as sacrificial template having the drug molecules adsorbed on the silica surface of pore walls. These findings uncover a new concept of storage and release of hydrophobic bioactive molecules.

Ordered mesoporous silicates as matrices for controlled release of drugs

Interest in and thereby also development of ordered mesoporous silicates as drug delivery devices have grown immensely over the past few years. On hand selected cases from the literature, the power of such systems as delivery devices has been established. Specifically, it is shown how it is possible to enhance the release kinetics of poorly soluble drugs by embedding them in mesoporous silicates. Further critical factors governing the structure and release of the model drug itraconazole incorporated in an SBA-15 matrix are briefly reviewed. The possibility of functionalizing the surface of mesoporous matrices also under harsher conditions offers a broad platform for the design of stimuli-responsive drug release, including pH responsive systems and systems which respond to the presence of specific ions, reducing agents, magnetic field or UV light, whose efficiency and biocompatibility has been established in vitro.

Incorporation of antimicrobial compounds in mesoporous silica film monolith

Incorporation of the antimicrobial peptide LL-37 (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES), as well as low molecular weight antimicrobial chlorhexidine, into mesoporous silica was obtained using an EISA one-pot synthesis method. FTIR confirmed efficient encapsulation of both LL-37 and chlorhexidine into mesoporous silica, while XRD and TEM showed that antimicrobial agent incorporation can be achieved without greatly affecting the structure of the mesoporous silica. The modified mesoporous silica released LL-37 and chlorhexidine slowly, reaching maximum release after about 200 h. The release rate could also be controlled through incorporation of SH groups in the pore walls, adding to pore hydrophobicity and reducing the release rate by about 50% compared to the unmodified mesoporous silica. Mesoporous silica containing either LL-37 or chlorhexidine displayed potent bactericidal properties against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. While chlorhexidine-loaded mesoporous silica displayed an accompanying high toxicity, as judged from hemolysis, LDH release, and MTT assay, the corresponding material containing LL-37 showed very low toxicity by all these assays, comparable to that observed for mesoporous silica in the absence of antibacterial drug, as well as to the negative controls in the respective assays. Mesoporous silica containing LL-37 therefore holds potential as an implantable material or a surface coating for such materials, as it combines potent bactericidal action with low toxicity, important features for controlling implant-related infections, e.g., for multi-resistant pathogens or for cases where access to the infection site of systemically administered antibiotics is limited due to collagen capsule formation or other factors.

The biocompatibility of mesoporous silicates

Micro- and nano-mesoporous silicate particles are considered potential drug delivery systems because of their ordered pore structures, large surface areas and the ease with which they can be chemically modified. However, few cytotoxicity or biocompatibility studies have been reported, especially when silicates are administered in the quantities necessary to deliver low-potency drugs. The biocompatibility of mesoporous silicates of particle sizes approximately 150 nm, approximately 800 nm and approximately 4 microm and pore sizes of 3 nm, 7 nm and 16 nm, respectively, is examined here. In vitro, mesoporous silicates showed a significant degree of toxicity at high concentrations with mesothelial cells. Following subcutaneous injection of silicates in rats, the amount of residual material decreased progressively over 3 months, with good biocompatibility on histology at all time points. In contrast, intra-peritoneal and intra-venous injections in mice resulted in death or euthanasia. No toxicity was seen with subcutaneous injection of the same particles in mice. Microscopic analysis of the lung tissue of the mice indicated that death may be due to thrombosis. Although local tissue reaction to mesoporous silicates was benign, they caused severe systemic toxicity. This toxicity might be mitigated by modification of the materials.

Temperature-controlled photooxygenation with polymer nanocapsules encapsulating an organic photosensitizer

A cross-linked poly- N-isopropylacrylamide (polyNIPAM) nanocapsule, TH@PC, containing thionine (TH), an organic photosensitizer, has been synthesized. This capsulated polymeric photosensitizer promotes a singlet oxygen oxygenation ( (1)O 2) accurately controlled by temperature: it shows high oxygenation activity at low temperature, but shows activity decrease with a rise in temperature, resulting in almost zero activity at >40 degrees C. The clear on-off activity control is driven by a heat-induced structure change of the capsule from the swollen single capsule to contracted state, and then to aggregate, behaving as an intelligent (1)O 2 filter. At low temperature, the capsule exists as the swollen single capsule, which allows (1)O 2 diffusion to bulk water, resulting in high oxygenation activity. A rise in temperature leads to contraction of the capsule, reducing the mesh size of the capsule wall. This suppresses (1)O 2 diffusion to bulk water and shows decreased activity. Intercapsule aggregation at >30 degrees C further suppresses (1)O 2 diffusion and shows almost no activity. The capsule promotes reversible activity control regardless of the heating/cooling process and can be reused with a simple recovery process.