Synthesis and Functionalization of Ordered Large-Pore Mesoporous Silica Nanoparticles for Biomedical Applications

Polymerization within Nanoporous Anodized Alumina Oxide Templates (AAO): A Critical Survey

In the last few years, the polymerization of monomers within the nanocavities of porous materials has been thoroughly studied and developed, allowing for the synthesis of polymers with tailored morphologies, chemical architectures and functionalities. This is thus a subject of paramount scientific and technological relevance, which, however, has not previously been analyzed from a general perspective. The present overview reports the state of the art on polymerization reactions in spatial confinement within porous materials, focusing on the use of anodized aluminum oxide (AAO) templates. It includes the description of the AAO templates used as nanoreactors. The polymerization reactions are categorized based on the polymerization mechanism. Amongst others, this includes electrochemical polymerization, free radical polymerization, step polymerization and atom transfer radical polymerization (ATRP). For each polymerization mechanism, a further subdivision is made based on the nature of the monomer used. Other aspects of "in situ" polymerization reactions in restricted AAO geometries include: conversion monitoring, kinetic studies, modeling and polymer characterization. In addition to the description of the polymerization process itself, the use of polymer materials derived from polymerization in AAO templates in nanotechnology applications, is also highlighted. Finally, the review is concluded with a general discussion outlining the challenges that remain in the field.

Multiple Roles of Mesoporous Silica in Safe Pesticide Application by Nanotechnology: A Review

Pollution related to pesticides has become a global problem due to their low utilization and non-targeting application, and nanotechnology has shown great potential in promoting sustainable agriculture. Nowadays, mesoporous silica-based nanomaterials have garnered immense attention for improving the efficacy and safety of pesticides due to their distinctive advantages of low toxicity, high thermal and chemical stability, and particularly size tunability and versatile functionality. Based on the introduction of the structure and synthesis of different types of mesoporous silica nanoparticles (MSNs), the multiple roles of mesoporous silica in safe pesticide application using nanotechnology are discussed in this Review: (i) as nanocarrier for sustained/controlled delivery of pesticides, (ii) as adsorbent for enrichment or removal of pesticides in aqueous media, (iii) as support of catalysts for degradation of pesticide contaminants, and (iv) as support of sensors for detection of pesticides. Several scientific issues, strategies, and mechanisms regarding the application of MSNs in the pesticide field are presented, with their future directions discussed in terms of their environmental risk assessment, in-depth mechanism exploration, and cost-benefit consideration for their continuous development. This Review will provide critical information to related researchers and may open up their minds to develop new advances in pesticide application.

Enlarged Pore Size Chiral Mesoporous Silica Nanoparticles Loaded Poorly Water-Soluble Drug Perform Superior Delivery Effect

Large mesopores of chiral silica nanoparticles applied as drug carrier are worth studying. In this study, chiral mesoporous silica nanoparticles (CMSN) and enlarged chiral mesoporous silica nanoparticles (E-CMSN) with a particle size from 200 to 300 nm were synthesized. Fourier transform infrared spectrometer (FTIR), circular dichroism spectrum, scanning electron microscopy (SEM), transmission electron microscope (TEM), and nitrogen adsorption/desorption measurement were adopted to explore their characteristics. The results showed that the surface area, pore volume, and pore diameter of E-CMSN were higher than those of CMSN due to enlarged mesopores. Poorly water-soluble drug nimesulide (NMS) was taken as the model drug and loaded into carriers using adsorption method. After NMS was loaded into CMSN and E-CMSN, most crystalline NMS converted to amorphous phase and E-CMSN was superior. The anti-inflammatory pharmacodynamics and in vivo pharmacokinetics results were consistent with the wetting property and in vitro drug dissolution results, verifying that NMS/E-CMSN exhibited superior NMS delivery system based on its higher oral relative bioavailability and anti-inflammatory effect because its enlarge mesopores contributed to load and release more amorphous NMS. The minor variations in the synthesis process contributed to optimize the chiral nano-silica drug delivery system.

Self-Regulated Carboxyphenylboronic Acid-Modified Mesoporous Silica Nanoparticles with "Touch Switch" Releasing Property for Insulin Delivery

Glucose-responsive insulin delivery systems, which can maintain a stable level of blood glucose, have been proposed as a promising method to treat diabetes. Such systems can reduce potential toxicity and enhance patient compliance compared to traditional therapies. Accordingly, we designed a mesoporous silica nanoparticle (MSN)-based glucose-sensitive and self-regulated drug release system to achieve the goal of long circulation and "touch switch" in vivo. In this system, carboxyphenylboronic acid (CPBA) was first modified on the surface of MSN using amidation reaction. Insulin (INS) was then loaded in the channels of MSN (CPBA-MSN/INS) through physical adsorption, and sodium alginate (SA) was introduced onto the surface of the CPBA-MSN/INS nanoparticles as the gatekeeper via amidation reaction (SA/CPBA-MSN/INS). We found the drug loading capacity of INS was 261 mg/g. In the normal range of blood glucose, INS was scarcely released due to the reversible covalent interaction between 1,2-diols of SA and CPBA. Within the high concentration of glucose, the boronate esters could be dissociated, which results in the mesoporous channels opening and the release of INS. In vivo experiments on diabetic mice showed SA/CPBA-MSN/INS sustained a normal blood glucose level for up to 12 h with a single dose. Moreover, the lipid metabolism disorder and organ damage of diabetic mice were alleviated after treatment with SA/CPBA-MSN/INS. Therefore, SA/CPBA-MSN/INS characterized by an "on-off" regulated drug release property and high biosafety shows promise for applications in diabetes treatment.

Nanoparticle mediated delivery and small molecule triggered activation of proteins in the nucleus

Protein transfection is a versatile tool to study or manipulate cellular processes and also shows great therapeutic potential. However, the repertoire of cost effective techniques for efficient and minimally cytotoxic delivery remains limited. Mesoporous silica nanoparticles (MSNs) are multifunctional nanocarriers for cellular delivery of a wide range of molecules, they are simple and economical to synthesize and have shown great promise for protein delivery. In this work we present a general strategy to optimize the delivery of active protein to the nucleus. We generated a bimolecular Venus based optical sensor that exclusively detects active and bioavailable protein for the performance of multi-parameter optimization of protein delivery. In conjunction with cell viability tests we maximized MSN protein delivery and biocompatibility and achieved highly efficient protein transfection rates of 80%. Using the sensor to measure live-cell protein delivery kinetics, we observed heterogeneous timings within cell populations which could have a confounding effect on function studies. To address this problem we fused a split or dimerization dependent protein of interest to chemically induced dimerization (CID) components, permitting control over its activity following cellular delivery. Using the split Venus protein we directly show that addition of a small molecule dimerizer causes synchronous activation of the delivered protein across the entire cell population. This combination of cellular delivery and triggered activation provides a defined starting point for functional studies and could be applied to other protein transfection methods.

A Review of Recent Developments of Mesoporous Materials

This personal account concerns novel recent discoveries in the area of mesoporous materials. Most of the papers discussed have been published within the last two to three years. A major emphasis of most of these papers is the synthesis of unique mesoporous materials by a variety of synthetic methods. Many of these articles focus on the control of the pore sizes and shapes of mesoporous materials. Synthetic methods of various types have been used for such control of porosity including soft templating, hard templating, nano-casting, electrochemical methods, surface functionalization, and trapping of species in pores. The types of mesoporous materials range from carbon materials, metal oxides, metal sulfides, metal nitrides, carbonitriles, metal organic frameworks (MOFs), and composite materials. The vast majority of recent publications have centered around biological applications with a majority dealing with drug delivery systems. Several other bio-based articles on mesoporous systems concern biomass conversion and biofuels, magnetic resonance imaging (MRI) studies, ultrasound therapy, enzyme immobilization, antigen targeting, biodegradation of inorganic materials, applications for improved digestion, and antitumor activity. Numerous nonbiological applications of mesoporous materials have been pursued recently. Some specific examples are photocatalysis, photo-electrocatalysis, lithium ion batteries, heterogeneous catalysis, extraction of metals, extraction of lanthanide and actinide species, chiral separations and catalysis, capturing and the mode of binding of carbon dioxide (CO₂ ), optical devices, and magneto-optical devices. Of this latter class of applications, heterogeneous catalysis is predominant. Some of the types of catalytic reactions being pursued include hydrogen generation, selective oxidations, aminolysis, Suzuki coupling and other coupling reactions, oxygen reduction reactions (ORR), oxygen evolution reactions (OER), and bifunctional catalysis. For perspective, there have been over 40,000 articles on mesoporous materials published in the last 4 years and about 1388 reviews. By no means is this personal account thorough or all inclusive. One objective has been to choose a variety of articles of different types to obtain a flavor of the breadth of diversity involved in the area of mesoporous materials.