Mesoporous silica nanoparticles: Their potential as drug delivery carriers and nanoscavengers in Alzheimer's and Parkinson's diseases

Worldwide, populations face significant burdens from neurodegenerative disorders (NDDs), especially Alzheimer's and Parkinson's diseases. Although there are many proposed etiologies for neurodegenerative disorders, including genetic and environmental factors, the exact pathogenesis for these disorders is not fully understood. Most patients with NDDs are given lifelong treatment to improve their quality of life. There are myriad treatments for NDDs; however, these agents are limited by their side effects and difficulty in passing the blood-brain barrier (BBB). Furthermore, the central nervous system (CNS) active pharmaceuticals could offer symptomatic relief for the patient's condition without providing a complete cure or prevention by targeting the disease's cause. Recently, Mesoporous silica nanoparticles (MSNs) have gained interest in treating NDDs since their physicochemical properties and inherent ability to pass BBB make them possible drug carriers for several drugs for NDDs treatment. This paper provides insight into the pathogenesis and treatment of NDDs, along with the recent advances in applying MSNs as fibril scavengers. Moreover, the application of MSNs-based formulations in enhancing or sustaining drug release rate, and brain targeting via their responsive release properties, besides the neurotoxicity of MSNs, have been reviewed.

A glutathione disulfide-sensitive Janus nanomachine controlled by an enzymatic AND logic gate for smart delivery

This work describes the assembly of a novel enzyme-controlled nanomachine operated through an AND Boolean logic gate for on-command delivery. The nanodevice was constructed on Au-mesoporous silica Janus nanoparticles capped with a thiol-sensitive gate-like molecular ensemble on the mesoporous face and functionalized with glutathione reductase on the gold face. This autonomous nanomachine employed NADPH and glutathione disulfide as input chemical signals, leading to the enzymatic production of reduced glutathione that causes the disruption of the gating mechanism on the mesoporous face and the consequent payload release as an output signal. The nanodevice was successfully used for the autonomous release of doxorubicin in HeLa cancer cells and RAW 264.7 macrophage cells.

Janus nanocarrier powered by bi-enzymatic cascade system for smart delivery

We report herein the assembly of an integrated nanodevice with bi-enzymatic cascade control for on-command cargo release. This nanocarrier is based on Au-mesoporous silica Janus nanoparticles capped at the mesoporous face with benzimidazole/β-cyclodextrin-glucose oxidase pH-sensitive gate-like ensembles and functionalized with invertase on the gold face. The rationale for this delivery mechanism is based on the invertase-mediated hydrolysis of sucrose yielding glucose, which is further transformed into gluconic acid by glucose oxidase causing the disruption of the pH-sensitive supramolecular gates at the Janus nanoparticles. This enzyme-powered device was successfully employed in the autonomous and on-demand delivery of doxorubicin in HeLa cancer cells.

All-metallic nanorattles consisting of a Pt core and a mesoporous PtPd shell for enhanced electrocatalysis

The fabrication of nanorattles with controllable compositions and structures is very important for catalytic applications. Herein, we propose a facile method for synthesis of very unique all-metallic nanorattle consisting of a Pt core and a mesoporous PtPd shell (named Pt@mPtPd). Owing to its spatially and locally separated active inner Pt core and mesoporous PtPd shell, the Pt@mPtPd nanorattle shows the enhanced performance for oxygen reduction reaction. The newly designed Pt@mPtPd nanorattle is quite different from traditional nanorattles with porous carbon and silica shell in its catalytically functional mesoporous metallic shell. The proposed facile method is highly valuable for the design of all-metallic nanorattle with controllable compositions and desired functions.

A dual-functional HER2 aptamer-conjugated, pH-activated mesoporous silica nanocarrier-based drug delivery system provides in vitro synergistic cytotoxicity in HER2-positive breast cancer cells

Purpose: As well as functioning as a ligand that is selectively internalized by cells overexpressing human epidermal growth factor receptor-2 (HER2), HApt can exert cytotoxic effects by inducing cross-linking and subsequent translocation of HER2 to cytoplasmic vesicles, such downregulation of HER2 inhibits cell proliferation and induces apoptosis. We aimed to exploit the potential of HApt as both a targeting agent and antagonist to maximize the efficacy of mesoporous silica nanoparticle (MSN)-based drug release systems for HER2-positive breast cancer. Materials and methods: We fabricated novel HApt aptamer-functionalized pH-sensitive β-cyclodextrin (β-CD)-capped doxorubicin (DOX)-loaded mesoporous silica nanoparticles (termed MSN-BM/CD-HApt@DOX) for targeted delivery and selective targeting of HER2-positive cells. MSN-functionalized benzimidazole (MSN-BM) was used to load and achieve pH stimuli-responsive release of the chemotherapeutic agent doxorubicin (DOX). β-cyclodextrin was introduced as a gatekeeper for encapsulated DOX and HApt as a selective HER2-targeting moiety and biotherapeutic agent. Results: Physical and chemical characterizations (FT-IR, XRD, TEM and BET) confirmed successful construction of MSN-BM/CD-HApt@DOX nanoparticles. In vitro release assays verified pH-sensitive DOX release. MSN-BM/CD-HApt@DOX (relative DOX concentration, 3.6 μg/mL) underwent HER2-mediated endocytosis and was more cytotoxic to HER2-positive SKBR3 cells than HER2-negative MCF7 cells. MSN-BM/CD-HApt@DOX also exhibited better uptake and stronger growth inhibition in SKBR3 cells than the control MSN-BM/CD-NCApt@DOX functionalized with a scrambled nucleotide sequence on CD. Overall, intracellular delivery of DOX and the biotherapeutic agent HApt resulted in synergistic cytotoxic effects in HER2-positive cancer cells in comparison to either DOX or HApt alone. Conclusion: MSN-BM/CD-HApt@DOX enables HER2-mediated targeting and biotherapeutic effects as well as pH-responsive DOX drug release, resulting in synergistic cytotoxic effects in HER2-overexpressing cells in vitro. This novel nanocarrier could potentially enable specific targeting to improve the efficacy of chemotherapy for HER2-positive cancer.

Facile Strategy for the Synthesis of Gold@Silica Hybrid Nanoparticles with Controlled Porosity and Janus Morphology

Hybrid materials prepared by encapsulation of plasmonic nanoparticles in porous silica systems are of increasing interest due to their high chemical stability and applications in optics, catalysis and biological sensing. Particularly promising is the possibility of obtaining gold@silica nanoparticles (Au@SiO₂ NPs) with Janus morphology, as the induced anisotropy can be further exploited to achieve selectivity and directionality in physical interactions and chemical reactivity. However, current methods to realise such systems rely on the use of complex procedures based on binary solvent mixtures and varying concentrations of precursors and reaction conditions, with reproducibility limited to specific Au@SiO₂ NP types. Here, we report a simple one-pot protocol leading to controlled crystallinity, pore order, monodispersity, and position of gold nanoparticles (AuNPs) within mesoporous silica by the simple addition of a small amount of sodium silicate. Using a fully water-based strategy and constant content of synthetic precursors, cetyl trimethylammonium bromide (CTAB) and tetraethyl orthosilicate (TEOS), we prepared a series of four silica systems: (A) without added silicate, (B) with added silicate, (C) with AuNPs and without added silicate, and (D) with AuNPs and with added silicate. The obtained samples were characterised by transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), and UV-visible spectroscopy, and kinetic studies were carried out by monitoring the growth of the silica samples at different stages of the reaction: 1, 10, 15, 30 and 120 min. The analysis shows that the addition of sodium silicate in system B induces slower MCM-41 nanoparticle (MCM-41 NP) growth, with consequent higher crystallinity and better-defined hexagonal columnar porosity than those in system A. When the synthesis was carried out in the presence of CTAB-capped AuNPs, two different outcomes were obtained: without added silicate, isotropic mesoporous silica with AuNPs located at the centre and radial pore order (C), whereas the addition of silicate produced Janus-type Au@SiO₂ NPs (D) in the form of MCM-41 and AuNPs positioned at the silica⁻water interface. Our method was nicely reproducible with gold nanospheres of different sizes (10, 30, and 68 nm diameter) and gold nanorods (55 × 19 nm), proving to be the simplest and most versatile method to date for the realisation of Janus-type systems based on MCM-41-coated plasmonic nanoparticles.

Amperometric aptasensor for carcinoembryonic antigen based on the use of bifunctionalized Janus nanoparticles as biorecognition-signaling element

We report herein the design of a novel biosensing strategy for the detection of carcinoembryonic antigen (CEA), based on the use of Janus-type nanoparticles having Au and silica opposite faces as integrated electrochemical biorecognition-signaling system. The Janus nanoparticles were properly functionalized with horseradish peroxidase on the silica surface to act as signaling element, and a biotin thiol-modified anti-CEA DNA hairpin aptamer the Au face to assemble the biorecognition element. The sensing approach relies on the first specific recognition of CEA by the bifunctionalized Janus nanoparticles, causing unfolding of the DNA hairpin structure and unmasking the biotin residues at the aptamer chain. This CEA-Janus nanoparticle complex was then captured by avidin-modified Fe₃O₄@SiO₂ NanoCaptors^®, allowing further magnetic deposition on carbon screen printed electrodes for the amperometric detection of the cancer biomarker. The Janus nanoparticles-based aptasensor was able to detect CEA in the range from 1 to 5000 ng mL^-1 (5.5 pM-28 nM) with a detection limit of 210 pg mL^-1 (1.2 pM). The aptasensor also showed high reproducibility and storage stability, and was successfully validated in human serum.

Janus nanoparticles in cancer diagnosis, therapy and theranostics

Anisotropic Janus nanoparticles (JNPs), due to their several distinct merits, have been widely investigated for cancer theranostics.

Hybrid Mesoporous Nanocarriers Act by Processing Logic Tasks: Toward the Design of Nanobots Capable of Reading Information from the Environment

Here, we present the design of smart nanodevices capable of reading molecular information from the environment and acting accordingly by processing Boolean logic tasks. As proof of concept, we prepared Au-mesoporous silica (MS) nanoparticles functionalized with the enzyme glucose dehydrogenase (GDH) on the Au surface and with supramolecular nanovalves as caps on the MS surface, which is loaded with a cargo (dye or drug). The nanodevice acts as an AND logic gate and reads information from the solution (presence of glucose and nicotinamide adenine dinucleotide (NAD⁺)), which results in cargo release. We show the possibility of coimmobilizing GDH and the enzyme urease on nanoparticles to mimic an INHIBIT logic gate, in which the AND gate is switched off by the presence of urea. We also show that such nanodevices can deliver cytotoxic drugs in cancer cells by recognizing intracellular NAD⁺ and the presence of glucose.

Mesoporous Silica and Organosilica Nanoparticles: Physical Chemistry, Biosafety, Delivery Strategies, and Biomedical Applications

Predetermining the physico-chemical properties, biosafety, and stimuli-responsiveness of nanomaterials in biological environments is essential for safe and effective biomedical applications. At the forefront of biomedical research, mesoporous silica nanoparticles and mesoporous organosilica nanoparticles are increasingly investigated to predict their biological outcome by materials design. In this review, it is first chronicled that how the nanomaterial design of pure silica, partially hybridized organosilica, and fully hybridized organosilica (periodic mesoporous organosilicas) governs not only the physico-chemical properties but also the biosafety of the nanoparticles. The impact of the hybridization on the biocompatibility, protein corona, biodistribution, biodegradability, and clearance of the silica-based particles is described. Then, the influence of the surface engineering, the framework hybridization, as well as the morphology of the particles, on the ability to load and controllably deliver drugs under internal biological stimuli (e.g., pH, redox, enzymes) and external noninvasive stimuli (e.g., light, magnetic, ultrasound) are presented. To conclude, trends in the biomedical applications of silica and organosilica nanovectors are delineated, such as unconventional bioimaging techniques, large cargo delivery, combination therapy, gaseous molecule delivery, antimicrobial protection, and Alzheimer's disease therapy.