Highly ordered functionalized mesoporous silicate nanoparticles reinforced poly (lactic acid) gatekeeper surface for infection treatment

The controlled release of a drug considers the key feature of the delivery carrier that enhances therapeutic efficacy. This study was aimed at design, synthesis of nano valve and capping systems onto caged functionalized mesoporous silica nanoparticles (SBA15) with nanoflowers polylactic acid (PLA-NF). Levofloxacin (LVX) as a specific model drug was encapsulated onto series; SBA15, SBA15@NH2, and SBA15@NH2/PLA. The examined nanocarriers released in a controlled fashion by external stimuli. The delivery vehicle based on PLA-NF coated SBA15@NH2, potent conjugated with LVX with experienced a high extent of trapping content with fast releasing by pH regulating mechanism. In vial LVX released profile and in vitro antifungal forceful of the selected microbes were detected. However, SBA15@NH2/PLA exhibited pore size, surface area and pore volume 5.4 nm, 163 and 0.011 respectively, but the significantly clear zone was obtained with Staphylococcus aureus ATCC 6538 (G+ve), Escherichia coli ATCC 25922 (G-ve), Candida albicans ATCC 10231 (yeast) and Aspergillus niger NRRL A-326 (fungus). Viability test avouch that rising functionality enhanced cytocompatibility and non-toxicity profile. Based on the aforementioned promising data, this type of nanocarriers offers when functionalized with targeting cells, the accessibility to deliver antibiotics onto nanosystem for increased potency against microbes and reduce side effects.

Synthesis of Colloidal Mesoporous Silica Spheres with Large Through-Holes on the Shell

Colloidal silica spheres with controllable large through-holes and mesopores on the shell were synthesized by using polystyrene (PS) spheres as a hard template and cationic surfactant hexadecyl trimethylammonium bromide (CTAB) as a soft template. Through modulating the synthetic conditions, including the volume ratio of ethanol (EtOH)/water, the amount of ammonia hydroxide, and the dosage of CTAB, SiO₂ spheres can transform among hollow structure, through-hole structure, and no large pore structure. The investigation suggests that the hydrolysis rate of the silica source and the interaction strength between the PS sphere template and SiO₂ may determine the large pore structure of the final product. The moderate hydrolysis rate of tetraethyl orthosilicate (TEOS) and strong interaction between the PS sphere template and SiO₂ is conductive to the formation of large through-holes in SiO₂ spheres. To further investigate the pore structure of through-holes of SiO₂ spheres, the lysozyme (Lz) was selected as a model molecule for adsorption experiments. The Lz adsorption experiments show that SiO₂ spheres with through-hole structure exhibit a much faster adsorption rate than SiO₂ spheres with hollow structure and higher adsorption capacity than SiO₂ with no large pore structure. Such a behavior could find interesting applications in the fields that require a fast-loading characteristic.

Syntheses and biomedical applications of hollow micro-/nano-spheres with large-through-holes

This review mainly discussed the syntheses and biomedical applications of hollow micro-/nano-spheres with large-through-holes in shells.

A novel functional group difference-based selective etching strategy for the synthesis of hollow organic silica nanospheres

CTES@TCPTES were synthesized by CTES and TCPTES, and then TC-HSNSs could be fabricated with the basic etching agent based on stability difference between core and shell.

Dendrimer-like hybrid particles with tunable hierarchical pores

Dendrimer-like silica particles with a center-radial dendritic framework and a synergistic hierarchical porosity have attracted much attention due to their unique open three-dimensional superstructures with high accessibility to the internal surface areas; however, the delicate regulation of the hierarchical porosity has been difficult to achieve up to now. Herein, a series of dendrimer-like amino-functionalized silica particles with tunable hierarchical pores (HPSNs-NH2) were successfully fabricated by carefully regulating and optimizing the various experimental parameters in the ethyl ether emulsion systems via a one-pot sol-gel reaction. Interestingly, the simple adjustment of the stirring rate or reaction temperature was found to be an easy and effective route to achieve the controllable regulation towards center-radial large pore sizes from ca. 37-267 (148 ± 45) nm to ca. 8-119 (36 ± 21) nm for HPSNs-NH2 with particle sizes of 300-700 nm and from ca. 9-157 (52 ± 28) nm to ca. 8-105 (30 ± 16) nm for HPSNs-NH2 with particle sizes of 100-320 nm. To the best of our knowledge, this is the first successful regulation towards center-radial large pore sizes in such large ranges. The formation of HPSNs-NH2 may be attributed to the complex cross-coupling of two processes: the dynamic diffusion of ethyl ether molecules and the self-assembly of partially hydrolyzed TEOS species and CTAB molecules at the dynamic ethyl ether-water interface of uniform small quasi-emulsion droplets. Thus, these results regarding the elaborate regulation of center-radial large pores and particle sizes not only help us better understand the complicated self-assembly at the dynamic oil-water interface, but also provide a unique and ideal platform as carriers or supports for adsorption, separation, catalysis, biomedicine, and sensor.

Hollow silica capsules with well-defined asymmetric windows in the shell

A straightforward and effective approach to fabricate porous silica capsules with well-defined asymmetric windows in the shell using raspberry-like templates has been developed. This process begins with the formation of a hierarchical template by chemically coupling a large polystyrene sphere to an ensemble of small, polystyrene latex spheres. The hierarchical template in conjunction with a hard templating method and spin-coating leads to silica capsules with well-defined, asymmetric pores (windows) in the outer shell. Proof-of-principle of this approach has been demonstrated using a 1500/110 nm hierarchical template. The silica capsules thus produced were characterized with scanning electron microscopy and STEM. The diameter of the capsules was ~1400 nm, and the outer opening of the windows was ~100 nm in size, consistent with the diameters of the core and satellite spheres considering the shrinkage due to the calcination. The inner opening was ~30 nm, which gives rise to an asymmetry factor, defined as the diameter of the outer window to the diameter of the inner window, of ~3. In another example, surface-bound capsules with an asymmetry factor of ~1 were made. Collectively, these windows can provide efficient pathways to connect the inside of the capsule to the outside and have potential for asymmetric diffusion and rectification.

Spherical silica micro/nanomaterials with hierarchical structures: synthesis and applications

This paper reviews the progress made recently in synthesis and applications of spherical silica micro/nanomaterials with multilevel (hierarchical) structures. The spherical silica micro/nanomaterials with hierarchical structures are classified into four main structural categories that include (1) hollow mesoporous spheres, (2) core-in-(hollow porous shell) spheres, (3) hollow spheres with multiple porous shells and (4) hierarchically porous spheres. Due to the complex structures and being focused on spherical silica micro/nanomaterials, some novel methods based on the combination of two routine methods or two surfactants, and some special synthetic strategies are proposed to produce the spherical silica micro/nanomaterials with hierarchical structures. Compared with the same-sized solid, porous or hollow silica spheres, these fantastic spherical silica micro/nanomaterials with hierarchical structures exhibit enhanced properties which may enable them to be used in broad and promising applications as ideal scaffolds (carriers) for biological, medical, and catalytic applications.

Hierarchically mesoporous silica nanoparticles: extraction, amino-functionalization, and their multipurpose potentials

Hierarchically mesoporous silica nanoparticles (HMSNs) with uniform morphology and structure and with a diameter of ca. 100-220 nm were facilely fabricated using water, ethanol and ethyl ether as cosolvents. Template extraction and amino-functionalization were performed toward the HMSNs. These hierarchical mesopores are supposed to possess more advantages than conventional monomodal mesopores. Amino-functionalized HMSNs were homogeneously grafted with fluorescent molecules and loaded with Au nanoparticles (NPs), respectively. The extracted HMSNs were also successfully used to construct antireflection and superhydrophilc coatings. Drug release experiments showed that HMSNs exhibit much quicker rates of drug release compared with conventional mesoporous NPs due to their hierarchically mesoporous structures.

Facile strategy for synthesis of silica/polymer hybrid hollow nanoparticles with channels

The silica/polymer hybrid hollow nanoparticles with channels and gatekeepers were successfully fabricated with a facile strategy by using thermoresponsive complex micelles of poly(ethylene glycol)-b-poly(N-isopropylacrylamide) (PEG-b-PNIPAM) and poly(N-isopropylacrylamide)-b-poly(4-vinylpyridine) (PNIPAM-b-P4VP) as the template. In aqueous solution, the complex micelles (PEG-b-PNIPAM/PNIPAM-b-P4VP) formed with the PNIPAM block as the core and the PEG/P4VP blocks as the mixed shell at 45 °C and pH 4.0. After shell cross-linking by 1,2-bis(2-iodoethoxyl)ethane (BIEE), tetraethylorthosilicate (TEOS) selectively well-deposited on the P4VP block and processed the sol-gel reaction. When the temperature was decreased to 4 °C, the PNIPAM block became swollen and further soluble, and the PEG-b-PNIPAM block copolymer escaped from the hybrid nanoparticles as a result of swelled PNIPAM and weak interaction between PEG and silica at pH 4.0. Therefore, the hybrid hollow silica nanoparticles with inner thermoresponsive PNIPAM as gatekeepers and channels in the silica shell were successfully obtained, which could be used for switchable controlled drug release. In the system, the complex micelles, as a template, could avoid the formation of larger aggregates during the preparation of the hybrid hollow silica nanoparticles. The thermoresponsive core (PNIPAM) could conveniently control the hollow space through the stimuli-responsive phase transition instead of calcination or chemical etching. In the meantime, the channel in the hybrid silica shell could be achieved because of the escape of PEG chains from the hybrid nanoparticles.

Fine-tuning of silica nanosphere structure by simple regulation of the volume ratio of cosolvents

Silica nanospheres with varied morphologies and pore structures, including mesoporous nanospheres, nanospheres with hierarchical pores (from 2 to 100 nm), and hollow nanospheres of mesoporous shell, were fabricated at room temperature simply by regulating the ethanol/ethyl ether volume ratio in the starting solution. The silica nanostructures were characterized by small-angle X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption measurements. Based on experimental results, a plausible mechanism for the structural regulation of mesoporous silicas has been put forward. These novel nanostructures of hierarchical pores provide an ideal scaffold for biological, medical, and catalytic applications.

Formation of hollow mesoporous silica nanoworm with two holes at the terminals

A chiral low-molecular-weight amphiphile, L- 18Ala11PyPF(6), was synthesized from L-alanine. Hollow silica nanoworms with circular pore channels parallel to the shell surfaces and holes at the terminals were prepared using the self-assemblies of it as templates via a single-templating approach. The formation of this hierarchical structure was studied by taking TEM images after different reaction time and changing reaction conditions. It was found that the morphologies of the amphiphile-silica assemblies changed gradually during the sol-gel transcription process.