Construction and properties of venlafaxine hydrochloride sustained release system based on hollow mesoporous silica microspheres

The aim of this work is to develop a venlafaxine hydrochloride sustained release system based on hollow mesoporous silica microspheres(HMSMs).HMSMs were innovatively prepared with tetraethyl silicate(TEOS)as the precursor and volatile n-heptane as a soft template.The obtained HMSMs show a well-defined hollow structure with an average size of 967 nm and pore volume of 0.85 cm^(3)/g,implying it is a potential drug carrier.Subsequently,venlafaxine hydrochloride(VF)was absorbed in the HMSMs with a content of 37.67% or so.The sustained release effect is further measured by the dissolution in-strument at 37℃ and 50 rpm in ultrapure water.The results showed that the HMSMs/VF system shows good sustained release properties compared with sustained release tablets with hydroxypropyl meth-ylcellulose as the main component.This HMSMs sustained release system appears to be a promising candidate for a sustained drug release.

Study on the morphological regulation mechanism of hollow silica microsphere prepared via emulsion droplet template

The morphology regulation of hollow silica microspheres is significant for their properties and applications. In this paper, hollow silica microspheres were formed through the hydrolysis and condensation reaction of tetraethyl orthosilicate(TEOS) at the interface of the emulsion droplet templates composed of liquid paraffin and TEOS, followed by dissolving paraffin with ethanol. The effects of various factors including the emulsifier structure and content, TEOS content, catalyst type, and the ethanol content in the continuous water phase on the particle size, shell thickness and morphology of the prepared hollow silica microspheres were studied in detail. The results show that the diffusion and contact of TEOS and water molecules as well as the hydrolysis condensation reaction of TEOS at the oil-water interface are two critical processes for the synthesis and morphological regulation of hollow silica microspheres. Cationic emulsifier with a hydrophobic chain of appropriate length is the prerequisite for the successful synthesis of hollow silica microspheres. The ethanol content in water phase is the dominant factor to determine the average diameter of hollow microspheres, which can vary from 96 nm to 660 nm with the increase of the volume ratio of alcohol-water from 0 to 0.7. The silica wall thickness varies with the content and the hydrophobic chain length of the emulsifier, TEOS content, and the activity of the catalyst. The component of the soft template will affect the morphology of the silica wall. When the liquid paraffin is replaced by cyclohexane, hollow microspheres with fibrous mesoporous silica wall are fabricated. This work not only enriches the basic theory of interfacial polymerization in the emulsion system, but also provides ideas and methods for expanding the morphology and application of hollow silica microspheres.

Modulated Photon Emission of Eu^3＋ in Microsphere Cavity

Fused silica microsphere with a few Eu^3＋ ions on the equator is fabricated. The photon emission sharply modulated by whispering gallery （WG） modes is observed under excitation of 395 nm laser, which is in agreement with the prediction in theory. The quality factor of the WG modes in microsphere is estimated larger than 3000 from the emission spectrum, which is limited by our monochrometer. It proves that pumping Eu^3＋ in microsphere cavity in free space is feasible, and this system seems suitable for realizing strong coupling in future quantum computation purposes.

Synthesis of mesoporous silica microspheres by a spray-assisted carbonation microreaction method

A novel spray-assisted carbonation microreaction method for the synthesis of mesoporous silica microspheres is reported.The synthetic process comprises the preparation of a silica sol via a carbonation reaction,rapid gelation at high temperature,and subsequent rapid solvent evaporation by spray drying.The carbonation microreaction was conducted in a membrane dispersion microreactor,in the presence of sodium silicate and carbon dioxide reactants.The as-synthesized silica microspheres exhibit a uniform mesostructure,excellent dispersity,and a narrow particle size distribution,with average diameters of 1-2 μm,Brunauer-Emmett-Teller surface areas of 300-1149m2/g,and total pore volumes of 0.21-1.82 cm3/g.Relatively low concentrations of the silicate species and well-controlled silica condensation rates are responsible for the formation of the observed spherical morphology.The synthetic process is of significant practical importance as a result of using low-cost raw materials,and because of the excellent controllability and process stability displayed.Furthermore,this rapid and flexible method may be extended to the synthesis of various silica materials and their composites.

Facile one-pot emulsion/sol-gel method for preparing wrinkled silica microspheres

The present manuscript describes a facile and versatile method for preparing uniform wrinkled silica microspheres with diameters of tens of microns.The method comprises a one-pot emulsion/sol-gel method using silica precursors of organosilane and tetraethoxysilane.By controlling the sol-to-gel transition of the silica precursors,a series of silica microspheres based on uniform emulsion droplets was synthesized by membrane emulsification.The silica microspheres had a variety of surface morphologies ranging from smooth,maze-like wrinkles to polygon-like ravines.It was possible to alter the surface morphologies of the microspheres by controlling the amount of organosilane in the dispersed phase and the amount of ammonia catalyst in the continuous phase of the emulsion.The grooves on the wrinkled microspheres were able to trap polymer nanoparticles of matching size,thereby demonstrating the potential usefulness of the microspheres in separation science and drug delivery.

Observation of high-Q optomechanical modes in the mounted silica microspheres

An efficient method to mount a coupled silica microsphere and tapered fiber system is proposed and demonstrated experimentally. For the purpose of optomechanical studies, high-quality-factor optical(Q_o～ 10~8) and mechanical modes(Q_m～ 0.87 × 10~4) are maintained after the mounting process. For the mounted microsphere, the coupling system is more stable and compact and, thus, is beneficial for future studies and applications based on optomechanical interactions. Especially, the packaged optomechanical system, which is tested in a vacuum chamber,paves the way toward quantum optomechanics research in cryostat.

Mesoporous Silica Microspheres Composited with SBA-15s for Resonance Frequency Reduction in a Miniature Loudspeaker

Microspheres composited with mesoporous SBA-15 particles and silica were investigated as fillers in miniature loudspeakers to study the factors influencing the resonance frequency offsets(RFOs).Mesoporous silica microspheres(MSMs)were prepared by self-assembling SBA-15 mesoporous silica in a microemulsion synthesis system.The formation process involved the fabrication of a stable O/W microemulsion of tetrabutyl orthosili-cate(TBOS)and hexadecyltrimethylammonium bromide(C16TAB)and encapsulation of SBA-15s.The RFO increased and then decreased with increasing particle size(in the length range of 0.7—5.5 μm and in the width range of 0.2—0.45 μm),increased with increasing pore size(in the range of 7.0—9.4 nm)of SBA-15s,and increased with decreasing particle size(105—900 μm)of MSMs.