Biodegradability of mesoporous silica nanoparticles

Biodegradability significantly impacts the bioapplication of mesoporous silica nanoparticles (MSN). In recent years, immense efforts have been made to understand and tailor the biodegradability of MSN. In this mini review, we overview the recent reports on the biodegradation of MSN, with a focus on the correlation between biodegradation and physicochemical properties including specific surface area, morphology, pore size, particle diameter and condensation degree of silicon-oxygen network. In addition, strategies for improving the biodegradability of MSN such as metal ions and organic species doping are also introduced.     

Preparation of mesoporous benzene–silica nanoparticles

Nanoparticles of periodic mesoporous organosilica (PMO) with benzene bridging groups were prepared using a 1,4-bis(triethoxysilyl)benzene organosilica precursor and mixed surfactant templates composed of a poly(ethylene oxide)–poly(dl-lactic acid-co-glycolic acid)–poly(ethylene oxide) (PEO–PLGA–PEO) triblock copolymer and a fluorocarbon surfactant under acidic conditions. Mesoporous organosilica particles clearly exhibited a nanoscale diameter of 50–1000 nm by scanning electron microscopy. Moreover, these particles possessed a mesostructure with uniform pores in the range of 6.3–6.6 nm and core-shell type spherical morphology, which were confirmed by Synchrotron small angle X-ray scattering, transmission electron microscopy, and nitrogen adsorption analysis. Benzene bridging groups linked covalently to Si atoms were analyzed by solid state ¹³C- and ²⁹Si MAS NMR.     

中空介孔氧化硅纳米颗粒的制备及应用进展

集空腔与介孔结构于一体的中空介孔氧化硅纳米材料(HMSNs)因其高比表面积、可调孔径、低密度和高渗透等特性,而在诸多领域展现了极大的潜在应用前景。该文对中空-介孔氧化硅纳米颗粒的主要制备方法及其优缺点进行了概述,着重阐述了硬核模板法、液体界面组装法和界面重组与转换法的研究进展;同时,介绍了中空介孔氧化硅纳米颗粒在生物医药、催化和光学领域方面的应用。最后,对其制备和应用目前存在的挑战以及后续突破方向进行了分析和展望。     

中空介孔氧化硅纳米颗粒的制备及应用进展

集空腔与介孔结构于一体的中空介孔氧化硅纳米颗粒因其高比表面积、可调孔径、低密度和高渗透等特性,而在诸多领域展现了极大的潜在应用前景。本文对中空-介孔氧化硅纳米颗粒的主要制备方法及其优缺点进行了概述,着重阐述了硬核模板法、液体界面组装法和界面重组与转换法;同时介绍了中空介孔氧化硅纳米颗粒在生物医药、催化和光学领域的应用情况。最后,对其制备和应用存在的挑战和研究方向进行了分析和展望。     

Adsorption of acid dyes using polyelectrolyte impregnated mesoporous silica

Cationic polyelectrolyte, PDDA (Poly(diallyldimethylammonium chloride)), was impregnated on mesoporous silica SBA-15 (PDDA/SBA-15) and amorphous conventional silica (PDDA/CS) supports. Acid dye adsorption characteristics, such as adsorption kinetics, adsorption isotherms, maximum adsorption capacity, and breakthrough curves of the prepared PDDA/SBA-15 and PDDA/CS adsorbents, were examined by batch and column adsorption techniques where the Acid Violet 17, Acid Red 44, and Acid Blue 45 were used as target adsorbates. PDDA/SBA-15 adsorbent showed fast adsorption kinetics of less than 10 min and much higher adsorption capacities compared to PDDA/CS due to large pore sizes, ordered cylindrical pore structures, and high amount of impregnated PDDA. Results from batch and column experiments showed that practical use of PDDA/SBA-15 adsorbent for effective removal of acid dyes from aqueous solution would be possible. Polyelectrolyte impregnation method was suggested as a simple method for the development of adsorbent with large pore diameters and efficient adsorption characteristics.     

PEG-templated mesoporous silica nanoparticles exclusively target cancer cells

Mesoporous silica nanoparticles (MSNs) have been proposed as DNA and drug delivery carriers, as well as efficient tools for fluorescent cell tracking. The major limitation is that MSNs enter cells regardless of a target-specific functionalization. Here we show that non functionalized MSNs, synthesized using a PEG surfactant-based interfacial synthesis procedure, do not enter cells, while a highly specific, receptor mediated, cellular internalization of folic acid (FOL) grafted MSNs (MSN-FOL), occurs exclusively in folate receptor (FR) expressing cells. Neither the classical clathrin pathway nor macropinocytosis is involved in the MSN endocytic process, while fluorescent MSNs (MSN-FITC) enter cells through aspecific, caveolae-mediated, endocytosis. Moreover, internalized particles seem to be mostly exocytosed from cells within 96 h. Finally, cisplatin (Cp) loaded MSN-FOL were tested on cancerous FR-positive (HeLa) or normal FR-negative (HEK293) cells. A strong growth arrest was observed only in HeLa cells treated with MSN-FOL-Cp. The results presented here show that our mesoporous nanoparticles do not enter cells unless opportunely functionalized, suggesting that they could represent a promising vehicle for drug targeting applications.     

Surface-functionalized mesoporous silica nanoparticles as sorbents for BTEX

A series of octyl-functionalized and surfactant-containing mesoporous silica nanoparticle (MSN) materials were synthesized via a co-condensation method. The authors investigated the feasibility of the MSN materials as adsorbents for BTEX (benzene, toluene, ethylbenzene, and xylenes) in groundwater. Octyl group functionalization up to 1.5 mol octyl/kg MSN improved BTEX adsorption capacity, while the mesoporous structure was still maintained. The following trend in adsorption equilibrium and kinetics of each BTEX compound onto MSN was observed: p-xylene > ethylbenzene > = toluene > benzene. Pseudo-second-order rate constant for p-xylene adsorption onto MSN was 0.907 g/mmol.min, significantly higher than that of activated carbon (0.043 g/mol.min). Desorption/regeneration with methanol was completed in 2 h, and the regenerated MSN showed the adsorption capability equivalent to the original. We envision that the MSN material could serve as an efficient adsorbent for the removal of BTEX from aqueous phase.     

Multifunctional mesoporous silica nanocomposite nanoparticles for theranostic applications

Clever combinations of different types of functional nanostructured materials will enable the development of multifunctional nanomedical platforms for multimodal imaging or simultaneous diagnosis and therapy. Mesoporous silica nanoparticles (MSNs) possess unique structural features such as their large surface areas, tunable nanometer-scale pore sizes, and well-defined surface properties. Therefore, they are ideal platforms for constructing multifunctional materials that incorporate a variety of functional nanostructured materials. In this Account, we discuss recent progress by our group and other researchers in the design and fabrication of multifunctional nanocomposite nanoparticles based on mesoporous silica nanostructures for applications to simultaneous diagnosis and therapy. Versatile mesoporous silica-based nanocomposite nanoparticles were fabricated using various methods. Here, we highlight two synthetic approaches: the encapsulation of functional nanoparticles within a mesoporous silica shell and the assembly of nanoparticles on the surface of silica nanostructures. Various nanoparticles were encapsulated in MSNs using surfactants as both phase transfer agents and pore-generating templates. Using MSNs as a scaffold, functional components such as magnetic nanoparticles and fluorescent dyes have been integrated within these systems to generate multifunctional nanocomposite systems that maintain their individual functional characteristics. For example, uniform mesoporous dye-doped silica nanoparticles immobilized with multiple magnetite nanocrystals on their surfaces have been fabricated for their use as a vehicle capable of simultaneous magnetic resonance (MR) and fluorescence imaging and drug delivery. The resulting nanoparticle-incorporated MSNs were then tested in mice with tumors. These in vivo experiments revealed that these multifunctional nanocomposite nanoparticles were delivered to the tumor sites via passive targeting. These nanocomposite nanoparticles served as successful multimodal imaging probes and also delivered anticancer drugs to the tumor site. With innumerable combinations of imaging modalities and drug delivery available within these vehicles, multifunctional nanocomposite nanoparticles provide new opportunities for clinical diagnostics and therapeutics.     

Superhydrophilic coatings with enhanced transmittance fabricated from solid and mesoporous silica nanoparticles

Superhydrophilic coatings with high transmittance were fabricated from solid and mesoporous silica nanoparticles (NPs) via layer-by-layer assembly followed by calcination. These porous silica coatings were highly transparent and superhydrophilic. The maximum transmittance reached as high as 96.1%, while that of the glass substrate was 91%. The time for a droplet to spread flat (water contact angle lower than 5°) is <1?s. Scanning and transmission electron microscopies were used to observe the morphology and structure of both NPs and coating surfaces. Transmission spectra and their changes after calcination were characterized by UV–vis spectrophotometry. The surface wettability was studied using a contact angle/interface system.     

Use of nanoparticles for controlled release of biocides in solid wood

The fungicides tebuconazole and chlorothalonil were successfully incorporated into polymeric nanoparticles with median particle diameters of 100–250 nm. Polyvinylpyridine (PVPy) and polyvinylpyridine‐co‐styrene (10% styrene and 30% styrene) were employed as the polymer matrix. The size of the nanoparticle increased with increased styrene content. The biocide also affected particle size, with chlorothalonil consistently yielding larger nanoparticles than tebuconazole. The release of the biocides from the polymeric nanoparticles was studied by suspending them in water. The release rate of both tebuconazole and chlorothalonil decreased with increased styrene content in the matrix, and chlorothalonil consistently released more slowly from the polymeric nanoparticles than did tebuconazole. It was found that biocides were successfully introduced into solid wood by incorporating them within polymeric nanoparticles, suspending the nanoparticles in water, and using the suspension to treat the wood with conventional pressure treatments. Once in the wood, the polymer matrix serves as a reservoir for the biocide and controls its release rate into the wood. Southern pine sapwood samples were treated with biocide‐containing nanoparticles suspended in water, then exposed to the wood decay fungus Gloeophyllum trabeum using a simple wafer test. Samples exhibited fungal resistance at appropriate levels of biocide incorporation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 458–465, 2001     

Hollow mesoporous silica nanoparticles loaded with phosphomolybdate as smart anticorrosive pigment

Recent developments in surface science and technology open up new opportunities for the development of smart pigments through the integration of nanoscale containers loaded with active components into coatings. Regarding the external factor to trigger the inhibitor release, a change in pH is a very interesting stimulus since corrosion activity leads to local changes in pH. Although several types of nanocontainers and encapsulation approaches have been proposed and studied to meet this goal, mesoporous silica nanoparticles (MSNs) are especially interesting as they retain their solid properties as long as pH of the surrounding medium does not exceed ~11. On the other hand, the use of hollow mesoporous silica nanoparticles (HMSNs) with a large cavity inside each original mesoporous silica nanoparticle has recently gained increasing interest due to the higher loading capacity. In the present work, an environmentally friendly corrosion inhibitor with good anticorrosive behavior when applied on steel substrates, sodium phosphomolybdate, has been successfully loaded and encapsulated on HMSNs. The pH-dependent release of the corrosion inhibitor from the loaded/encapsulated HMSNs has been confirmed. In addition, an improved anticorrosive behavior of the coatings formulated with loaded/encapsulated HMSNs has been observed by Scanning Kelvin Probe (SKP).     

Functionalized self-assembled monolayers on mesoporous silica nanoparticles with high surface coverage

ABSTRACT: Mesoporous silica nanoparticles (MSNs) containing vinyl-, propyl-, isobutyl- and phenyl functionalized monolayers were reported. These functionalized MSNs were prepared via molecular self-assembly of organosilanes on the mesoporous supports. The relative surface coverage of the organic monolayers can reach up to 100% (about 5.06 silanes/nm.     

Synthesis of spherical mesoporous silica nanoparticles with nanometer-size controllable pores and outer diameters

Spherical mesoporous silica particles with tunable pore size and tunable outer particle diameter in the nanometer range were successfully prepared in a water/oil phase using organic templates method. This method involves the simultaneous hydrolytic condensation of tetraorthosilicate to form silica and polymerization of styrene into polystyrene. An amino acid catalyst, octane hydrophobic-supporting reaction component, and cetyltrimethylammonium bromide surfactant were used in the preparation process. The final step in the method involved removal of the organic components by calcinations, yielding the mesoporous silica particles. Interestingly, unlike common mesoporous materials, the particle with controllable pore size (4–15 nm) and particle diameter (20–80 nm) were produced using the method described herein. The ability to control pore size was drastically altered by the styrene concentration. The outer diameter was mostly controlled by varying the concentration of the hydrophobic molecules. Relatively large organic molecules (i.e. Rhodamine B) were well-absorbed in the prepared sample. Furthermore, the prepared mesoporous silica particles may be used efficiently in various applications, including electronic devices, sensors, pharmaceuticals, and environmentally sensitive pursuits, due to its excellent adsorption properties.     

非诺贝特/介孔二氧化硅的制备及缓释性能研究

采用单模板剂P123在强酸条件下合成具有二维六方相的SBA-15,采用双模板剂P123和F127在强酸条件下合成具有三维立方相的SBA-16。采用共沉淀法将非诺贝特负载于两种载体上,并通过扫描电镜(SEM)、高分辨透射电镜(HRTEM)、傅里叶红外光谱(FTIR)、X射线衍射(XRD)、N_2吸附-脱附的材料表征方法对载药前后载体材料的性质进行研究。结果表明,SBA-15和SBA-16孔径分别为5.77 nm和3.95 nm,比表面积分别为690.19 m²/g和807.02 m2/g和807.02 m²/g,载药量分别为32%和15%,载药后介孔材料的平均孔径、孔容及比表面积都有所降低。在不同pH溶出介质中,SBA-15和SBA-16两种介孔硅材料均起到一定缓释效果,酸性条件中,SBA-16缓释性能高于SBA-15,碱性条件下,两种材料缓释性能相近。     

介孔中空二氧化硅微球制备及吸附缓释性能研究

以用分散聚合法制得的不同粒径单分散阳离子型聚苯乙烯球为模板、十二胺为表面活性剂,通过溶胶-凝胶方法,在模板上包裹二氧化硅壳,并通过浸渍和焙烧制备了具有介孔结构的中空二氧化硅微球.TEM,SEM显示微球具有很好的单分散性和中空结构.小角XRD表明球壳上具有六方介孔结构.实验表明控制模板粒子大小可改变介孔中空二氧化硅微球粒径,改变正硅酸乙酯浓度可以调整二氧化硅球壳厚度.通过对丁基罗丹明B染料的吸附装载与释放实验证实了其有很好的渗透性和缓释性能.     

Tuning biodegradability and biocompatibility of mesoporous silica nanoparticles by doping strontium

Mesoporous silica nanoparticle (MSN), one of the most widely used nanomaterials, is of poor biodegradability in vivo due to its highly stable Si–O–Si structure. Here, the structural stability of Si–O–Si was regulated by doping strontium ion. Sr-doped MSNs (Sr-MSNs) were synthesized by a cetyltrimethylammonium-bromide-mediated template method and their phase, morphology, structure, physicochemical properties, in vitro degradability and cytocompatibility were investigated. Results indicated that Sr²⁺ was successfully incorporated into MSN with the collapse of the ordered mesoporous structure. Sr-doping significantly improved the specific surface area, in vitro degradability and cytocompatibility of MSN in a Sr-content-dependent manner. Particularly, excessive Sr-doping gave rise to generating impure strontium silicate which converted into disordered amorphous silica during degradation and hindered the biodegradable behaviors of MSN. Hence, the synthetic Sr-MSNs with excellent surface nature, biodegradability and biocompatibility were supposed to be applied as potential carriers for the controllable release of drugs and ions in numerous clinical applications.     

Growth and branching of gold nanoparticles through mesoporous silica thin films

Composite materials made of mesoporous oxide thin films containing metallic nanoparticles are of high interest in various fields, including catalysis, biosensing and non-linear optics. We demonstrate in this work the fabrication of such composite materials containing a sub-monolayer of gold nanoparticles (GNPs) of various shapes covered with mesoporous silica thin films. Additionally, the shape of the GNPs (and thus their optical properties) can be modified in situ through seeded growth and branching. Such growth proceeds upon wetting with HAuCl(4) solution, a surfactant (cetyltrimethylammonium bromide, CTAB) and a mild reducing agent (ascorbic acid, AA). The effect of varying several reaction parameters (time and CTAB and AA concentrations) was evaluated, showing that more anisotropic particles are obtained at longer reaction times, lower CTAB concentration and higher AA concentration. The final shape of the GNPs was also found to depend on their initial shape and size, as well as the pore size of the mesoporous film covering them. Because the growth proceeds through the pores of the film, it may lead to shapes that are not easily obtained in solution, such as particles with branches on one side only. Finally, we have confirmed that no damage was induced to the mesoporous silica structure during the growth process and thus the final particles remain well covered by the thin film, which can eventually be used as a filter between the GNPs and the outer medium.     

Periodic mesoporous silica and organosilica with controlled morphologies as carriers for drug release

In this paper, we report the effects of morphology, wall composition of mesoporous materials and different buffer solutions on drug delivery profiles. Hollow spheres of periodic mesoporous organosilica (PMO) were prepared and used as drug carriers which exhibited higher loading capacity and slower release rate compared to the conventional periodic mesoporous silica (PMS) spheres and solid spheres of PMO. This hollow PMO showed promising properties as a reservoir to encapsulate and store larger quantities of guest molecules within its “empty” core. Moreover, its organic reactive sites allowed stronger interactions to the hydrophobic guest molecules, in contrast to inorganic wall possessed by PMS materials. Antibiotic tetracycline was used as a model drug to study the effect of framework difference between PMO and PMS materials on the loading and release processes. Two kinds of release medium, simulated body fluid (SBF) solution (pH 7.4) and phosphate buffer (PB) solution (pH 1.5) were used in this study, which revealed very different release profiles. A slower delivery rate was observed in SBF solution, attributed to the different ionic interactions between the guest molecule and the host material in the two different pH solutions. Overall, hollow PMO shows the lowest release rate and the highest loading amount compared to the other two materials studied herein. The kinetic study reveals that drug release from host material follows the second order kinetic model better than the first order mass transfer model.     

功能化介孔二氧化硅纳米粒子在药物递送系统中的研究进展

综述了刺激响应型的介孔二氧化硅纳米粒子在药物递送系统中的研究进展,包括氧化还原型释药、磁响应型释药、温度响应型释药、pH响应型释药、酶响应型释药和联合刺激响应型释药,并对未来的发展方向进行了展望,以期为介孔二氧化硅粒子的功能化修饰以及实际应用提供参考。     

功能化介孔二氧化硅纳米粒子在药物递送系统中的研究进展

综述了刺激响应型的介孔二氧化硅纳米粒子在药物递送系统中的研究进展,包括氧化还原型释药、磁响应型释药、温度响应型释药、pH响应型释药、酶响应型释药和联合刺激响应型释药,并对未来的发展方向进行了展望,以期为介孔二氧化硅粒子的功能化修饰以及实际应用提供参考。