pH-Controlled drug release from mesoporous silica tablets coated with hydroxypropyl methylcellulose phthalate

A simple pH-controlled drug release system was successfully prepared by coating pH-sensitive polymer hydroxypropyl methylcellulose phthalate (HPMCP) on drug-loaded mesoporous SBA-15 tablet. Using famotidine (Famo) as a model drug, the effects of coating times and drying temperature on drug release were studied in detail to optimize the drug release system. In simulated gastric fluid (SGF, pH 1.2), it took only 2 h for Famo to be completely released from mesoporous silica tablet without HPMCP coating. Also in SGF, with the increase of coating times and drying temperature, the release of Famo was greatly delayed by HPMCP coating. For the tablet with twice coating of HPMCP and dried at 80 °C, only 4.0 wt.% of Famo could be released within 4 h. However, in simulated intestinal fluid (SIF, pH 7.4), HPMCP coating did not show obvious effect on the release of Famo.     

Dual-pH-sensitive mesoporous silica nanoparticle-based drug delivery system for tumor-triggered intracellular drug release

Reducing the side effects and improving the drug utilization are important work in anti-cancer drug delivery. In this paper, a novel dual-pH-sensitive drug delivery system was reported. Mesoporous silica nanoparticle (MSN) was applied to load anti-cancer drug doxorubicin hydrochloride (DOX) and was covered by mono-6-deoxy-6-EDA-β-cyclodextrine (β-CD-NH₂) to block the pores through pH-sensitive boronate ester bond. And the carriers were then coated with methoxy poly(ethylene glycol) (mPEG) through another pH-sensitive benzoic imine bond. mPEG leaving studies, in vitro cellular uptake studies and the flow cytometry analysis, proved that carriers was “stealthy” at pH 7.4, but could be “activated” for cytophagy by cancer cells in weakly acidic tumor tissues (pH 6.5) due to the departure of mPEG. β-CD-NH₂ leaving studies, the in vitro drug release studies and the in vitro cytotoxicity studies proved that boronate ester bond linking MSN and β-CD-NH₂ was stable at both pH 7.4 and 6.5, but could be hydrolyzed intracellular to release DOX for cellular apoptosis due to the lower pH (5.0). In summary, the novel dual-pH-sensitive drug delivery system fabricated with a dynamic protection strategy should have great application potential in anti-cancer drug delivery fields.     

Study of mesoporous silica/magnetite systems in drug controlled release

Ordered mesoporous materials like SBA-15 have a network of channels and pores with well-defined size in the nanoscale range. This particular silica matrix pore architecture makes them suitable for hosting a broad variety of compounds in very promising materials in a range of applications, including drug release magnetic carriers. In this work, magnetic nanoparticles embedded into mesoporous silica were prepared in two steps: first, magnetite was synthesized by oxidation-precipitation method, and next, the magnetic nanoparticles were coated with mesoporous silica by using nonionic block copolymer surfactants as structure-directing agents. The materials were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), N(2) adsorption, and scanning electron microscopy (SEM). The influence of magnetic nanoparticles on drug release kinetics was studied with cisplatin, carboplatin, and atenolol under in vitro conditions in the absence and in the presence of an external magnetic field (0.25 T) by using NdFeB permanent magnet. The constant external magnetic field did not affect drug release significantly. The low-frequency alternating magnetic field had a large influence on the cisplatin release profile.     

Thermo-sensitive poly(N-isopropylacrylamide)/ mesoporous silica nanocomposites as controlled delivery carriers: loading and release behaviors for drug ibuprofen

Thermo-sensitive nanocomposites based on mesoporous silica SBA-15 and poly(N-isopropylacrylamide) (PNIPAAm) have been synthesized via in situ radical polymerization in mesopores. The resultant materials were used as carriers to construct temperature-responsive controlled drug delivery systems. Loading of model drug ibuprofen (IBU) was ascertained by IR and UV-vis/DRS spectroscopy, and the mesostructure and pore properties of the delivery system were characterized by small-angle XRD and N2 adsorption-desorption experiment. Study on drug uptake indicated that higher polymer content in the composite, higher IBU concentration in loading solution and lower loading temperature below the lower critical solution temperature (LCST) could increase the loading amount of IBU by means of interaction between IBU and polymer and trap effect of the polymer chains in pores. Different from the uptake of IBU, however, the release of drug followed a positive temperature-responsive manner, that is, the release was accelerated upon heating above the LCST, while decelerated and lasted for a longer period of time below the LCST. This feature allows the material to function as a reversible fast/slow transition switch or rate regulator responsive to environmental temperature and to be potentially interesting in controlled delivery and other smart application fields.     

Fabrication of nano silica dispersed permalloy composite coating

In aqueous solution, the agglomeration of silica nanopowder is a major problem which causes poor uniformity of electroplated surfaces. Silica surface is susceptible to moisture due to the hydroxyl group on its surface which causes the silica nanopowder to become agglomerated. In this study, silica nanoparticle dispersion in the electroplated layer is reported. From zeta potential analysis, silica nanopowder has a negatively charged surface in an alkaline bath. Silica nanopowder is less agglomerated in an alkaline bath than in an acidic bath due to the surface charge. Additives change the surface morphologies of the electroplated layer as well as the silica nanopowder contents. Comparing an alkaline bath and an acidic bath, the advantage of an additive to the electroplated layer is only observed in an alkaline bath. Types of sonicators and sonication periods are also surveyed for silica nanopowder dispersion. Sonication time can be reduced by a horn-type sonicator, and longer sonication time guaranteed better silica nanopowder dispersion.     

Facilitating drug release in mesoporous silica coated upconversion nanoparticles by photoacid assistance upon near-infrared irradiation

Near-infrared (NIR) light-triggered pH-manipulation has been realized by utilizing upconversion nanoparticle assisted ring-closing reactions of the conventional photoacid merocyanine (MC). This pH manipulation behavior was then used to regulate the switch of an acid-labile cap for facilitating drug release on the basis of mesoporous silica coated upconversion nanoparticles, in which the drug release rate and amount and the cell killing ability have been greatly improved upon NIR light irradiation due to the locally high concentration of H⁺ within pore channels that is generated by upconversion assisted MC. This proof of concept may provide a way to utilize NIR light to regulate pH change for new drug delivery system designs and applications in biomedical field.     

Single-step coating of mesoporous silica on cetyltrimethyl ammonium bromide-capped nanoparticles

A generalized, single-step synthesis procedure to coat individual cetyltrimethyl ammonium bromide- (CTAB) capped nanoparticles with a thin layer of mesoporous silica is outlined. This coating method was demonstrated on CTAB-capped Au nanorods and CTAB-transferred CdSe/ZnS quantum dots with silica coatings approximately 15 nm thick containing pores approximately 4 nm in diameter. This porous silica coating can serve as a platform for further surface modification to facilitate the rapid translation of nanoparticles to a wide range of end applications.     

Preparation of mesoporous Co-B catalyst via self-assembled triblock copolymer templates

Mesoporous Co-B with worm-like morphology was firstly prepared via reduction of cobalt acetate by potassium borohydride in the presence of triblock copolymer templates. The as-prepared mesoporous Co-B was characterized by Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption-desorption. During the hydrolysis of KBH₄, the mesoporous Co-B exhibited much higher catalytic activity than the regular Co-B. It is attributed to the larger specific surface area (163.77 m²/g) and mesoporous channels. The average H₂ generation rate of the mesoporous Co-B was 3523 mL/min g catalyst in 1.3 wt% NaOH + 13 wt.% KBH₄ solution at 286 K, which may give a successive H₂ supply for a 571 W polymer electrolyte membrane fuel cell (PEMFC) at 100% H₂ utilization. Furthermore, the as-prepared mesoporous Co-B with high specific surface area is expected to find applications in many catalytic hydrogenation reactions.     

Fabrication of refining mesoporous silica nanofibers via electrospinning

Refining mesoporous silica nanofibers were fabricated by electrospinning method. A triblock copolymer (Pluronic, P123, H(C₂H₅O)₂₀(C₃H₇O)₇₀(C₂H₅O)OH) was used as the structure direction agent and polyvinyl pyrrolidone (PVP) was employed to prepare refining nanofibers. SEM images showed that the refining fibers had an average diameter about 200-300 nm with smooth surface. FT-IR spectrum and TGA curve proved that P123 and PVP were removed from the fibers after a thermal treatment. It was found that the obtained silica nanofibers had mesoporous structure. The pore structures were characterized by XRD and the N₂ adsorption-desorption isotherm.     

Carbon nanomaterials as drug carriers: Real time drug release investigation

The use of carbon nanomaterials in biomedical applications and the cytotoxicity of these materials have been areas of great interest during the last decade. In vitro drug load and release, as well as in vivo animal tests, have been carried out using carbon nanomaterials. However, no comparison studies on the drug load and the release of different carbon nanomaterials have been reported. Here, we report on a real time investigation of the drug release of carbon black (CB) nanoparticles, carbon nanotubes (CNTs) and graphene oxide (GO), using rhodamine B (RB) as a model of drug. The binding of RB to the nanomaterials were characterized by FTIR and UV–vis. The mass loading capacities of these nanomaterials were also studied, showing that GO had the highest capacity. The real time drug release experiment indicated different accumulative release modes of these nanomaterials at different pH values, due to their different binding modes with RB, which is also discussed as being the reason for the mechanism differences. Moreover, the comparison of the drug release capacity of CNT–RB and f-CNT–RB (functionalized-CNT–RB) indicated an influence of hydrogen bonds in both drug loading and release, as the hydrogen bonds increased the loading capacity of the carbon nanotube after acid treatment and changed the drug release mechanism at pH 7.4. Thus, here we identified the drug release modes of the different carbon nanomaterials. The results of the influence of functional groups and hydrogen bonds point also out a potential way of controlling the drug release behavior of carbon nanomaterials by surface modification.     

不同模板剂制备囊泡状介孔SiO2的研究

单一表面活性剂(离子型和非离子型表面活性剂等)作模板或它们的复配体系作共模板均可合成囊泡状介孔SiO<,2>.综述了在不同的反应条件下以不同表面活性剂为模板,以无机或有机硅为前驱物来制备单室或多室囊泡状介孔SiO<,2>,总结了其在生物化学领域的应用,并对其发展前景进行了展望.     

Synthesis of nano grade hollow silica sphere via a soft template method

The nano grade hollow silica sphere (HSS) was synthesized by a novel soft template method. We found that the precipitate of aluminate had a porous structure that could be the soft template for HSS. After mixing the colloidal silica with the aluminate precipitate, the bubble trapped in this porous structure could form the nano grade HSS. The aluminate precipitate was removed by adjusting the pH of the slurry to approximately 1. The outside diameter, the specific surface, and the mean pore size diameter of the forming HSS were 60-90 nm, 571 m2/g, and 3 nm, respectively. The formed HSS was collected by modifying the surface with Si(OCH3)3CHCH2 (VTMO) and then filtrating the precipitated gel in the n-butanol and ethanol solvent system.     

Pharmacological activity of ibuprofen released from mesoporous silica

Novel drug delivery systems (DDS) to improve the pharmacokinetic profile of hydrophobic drugs following oral administration are an area of keen interest in drug research. An ideal DDS should not adversely affect drug activity, be capable of delivering a therapeutic dose of drug, and allow homogenous drug loading and drug release. Mesoporous silica has been proposed for this application, with ibuprofen employed as the model drug. It was hypothesised that mesoporous silica MCM-41 is capable of delivering a pharmacologically therapeutic dose of ibuprofen. Ibuprofen-loaded MCM-41 can be prepared reproducibly at a drug to carrier ratio of 30% (wt/wt). The release profile was seen to be 90% within 2 h. Initial assessment of COX-1 inhibitory activity suggests the absence of adverse effects attributable to drug-carrier interaction. The results of this study provide further evidence in support of the proposed use of mesoporous silica in drug delivery.     

Strontium-substituted,luminescent and mesoporous hydroxyapatite microspheres for sustained drug release

The multifunctional strontium (Sr)-substituted hydroxyapatite microsphere was prepared via hydrothermal method, in which the luminescent and controlled drug release functions can be realized. The structure and morphology of the as-prepared microspheres were studied by using XRD, FTIR, SEM, TEM, HR-TEM, BET method. The optical properties was investigated by using photoluminescence (PL) and XPS measurement. Then, the as-prepared multifunctional microspheres were performed as a drug delivery carrier using vancomycin as a model drug. The experimental results show that the composition, morphology, luminescent properties and drug storage/release behaviour were obviously influenced by the amount of Sr. The microspheres with Sr²⁺/(Ca²⁺ + Sr²⁺) = 0.3 of Sr substitution showed the maximum specific surface area, best pore structure and strongest PL intensity. All the samples presented remarkable sustained drug release kinetics. In addition, the PL intensity of SrHA in the drug delivery system increased with the cumulative release time (amount) of vancomycin, which would make the drug release might be possibly tracked by the change of the luminescent intensity. Our study indicated a potential prospect that the fabricated multifunctional SrHA mesoporous microspheres might be applied in the field of bone regeneration and drug delivery.     

Real-time imaging of tunable adenosine 5-triphosphate release from an MCM-41-type mesoporous silica nanosphere-based delivery system

We studied a mesoporous silica nanosphere (MSN) material with tunable release capability for drug delivery applications. We employed luciferase chemiluminescence imaging to investigate the kinetics and mechanism of the adenosine 5-triphosphate (ATP) release with various disulfide-reducing agents as uncapping triggers. ATP molecules were encapsulated within the MSNs by immersing dry nanospheres in aqueous solutions of ATP followed by capping of the mesopores with chemically removable caps, such as cadmium sulfide (CdS) nanoparticles and poly(amido amine) dendrimers (PAMAM), via a disulfide linkage. By varying the chemical nature of the 'cap' and 'trigger' molecules in our MSN system, we discovered that the release profiles could indeed be regulated in a controllable fashion.     

Facile synthesis by a covalent binding reaction for pH‐responsive drug release of carboxylated chitosan coated hollow mesoporous silica nanoparticles

In this study, a promising drug nano‐carrier system consisting of mono‐dispersed and pH sensitive carboxylated chitosan‐hollow mesoporous silica nanoparticles (Ccs‐HMSNs) suitable for the treatment of malignant cells was synthesised and investigated. At neutral pH, the Ccs molecules are orderly aggregated state, which could effectively hinder the release of loaded drug molecules. However, in slightly acidic environment, Ccs chains are heavily and flexibly entangled in gel state, which would enhance the subsequent controlled release of the loaded drug. Using doxorubicin hydrochloride (DOX•HCl) as the drug model, their results demonstrated that the system had an excellent loading efficiency (64.74 μg/mg Ccs‐HMSNs) and exhibited a pH‐sensitive release behaviour. Furthermore, confocal laser scanning microscopy revealed that the Ccs‐HMSNs nanocomposite could effectively deliver and release DOX•HCl to the nucleus of HeLa cells, thereby inducing apoptosis. In addition, MTT assay also confirmed that DOX•HCl loaded Ccs‐HMSNs (DOX•HCl@Ccs‐HMSNs) exhibited a good anticancer effect on HeLa cells with a time‐dependent manner. Finally, haemolysis experiment showed Ccs‐HMSNs had no haemolytic activity at all the tested concentrations (5–320 μg/mL). Thus, this biocompatible and effective nano‐carrier system will have potential applications in controllable drug delivery and cancer therapy.Inspec keywords: drug delivery systems, mesoporous materials, silicon compounds, nanoparticles, nanocomposites, nanofabrication, drugs, nanomedicine, biomedical materials, pH, aggregation, gels, optical microscopy, cellular biophysics, cancer, filled polymersOther keywords: facile synthesis, covalent binding reaction, pH‐responsive drug release, carboxylated chitosan coated hollow mesoporous silica nanoparticles, drug nanocarrier system, monodispersed carboxylated chitosan‐hollow mesoporous silica nanoparticles, pH sensitive carboxylated chitosan‐hollow mesoporous silica nanoparticles, malignant cell treatment, neutral pH, orderly aggregated state, loaded drug molecules, acidic environment, gel state, doxorubicin hydrochloride, drug model, confocal laser scanning microscopy, nanocomposite, HeLa cells, apoptosis, MTT assay, anticancer effect, haemolysis experiment, biocompatible nanocarrier system, drug delivery, cancer therapy, SiO₂      

Hierarchical mesoporous silica nanotubes derived from natural cellulose substance

Bioinspired synthesis of hierarchical mesoporous silica nanotubes by using natural cellulose substance (filter paper) and cetyltrimethylammonium bromide (CTAB) micelles as dual templates was achieved. CTAB micelles were adsorbed onto the surfaces of ultrathin titania film precoated cellulose nanofibers, followed by hydrolysis and condensation of tetraethyl orthosilicate around these micelles to form silica. After calcination and sulfuric acid treatment to remove the organic templates and the thin titania film, bulk white sheets composed of natural hierarchical silica nanotubes with mesopores in the walls were obtained, to which silver nanoparticles were further induced to give a silica-nanotube/metal-nanoparticle hybrid.     

Polymer-grafted hollow mesoporous silica nanoparticles integrated with microneedle patches for glucose-responsive drug delivery

A glucose-mediated drug delivery system would be highly satisfactory fordiabetes diagnosis since it can intelligently release drug based on blood glucose levels.Herein,a glucose-responsive drug delivery system by integrating glucose-responsivepoly(3-acrylamidophenylboronic acid)(PAPBA)functionalized hollow mesoporous silicananoparticles(HMSNs)with transcutaneous microneedles(MNs)has been designed.Thegrafted PAPBA serves as gatekeeper to prevent drug release from HMSNs atnormoglycemic levels.In contrast,faster drug release is detected at a typicalhyperglycemic level,which is due to the change of hydrophilicity of PAPBA at highglucose concentration.After transdermal administration to diabetic rats,an effectivehypoglycemic effect is achieved compared with that of subcutaneous injection.Theseobservations indicate that the designed glucose-responsive drug delivery system has apotential application in diabetes treatment.