Polymeric functionalization of mesoporous silica nanoparticles: Biomedical insights

Mesoporous silica nanoparticles (MSNs) endowed with polymer coatings present a versatile platform, offering notable advantages such as targeted, pH-controlled, and stimuli-responsive drug delivery. Surface functionalization, particularly through amine and carboxyl modification, enhances their suitability for polymerization, thereby augmenting their versatility and applicability. This review delves into the diverse therapeutic realms benefiting from polymer-coated MSNs, including photodynamic therapy (PDT), photothermal therapy (PTT), chemotherapy, RNA delivery, wound healing, tissue engineering, food packaging, and neurodegenerative disorder treatment. The multifaceted potential of polymer-coated MSNs underscores their significance as a focal point for future research endeavors and clinical applications. A comprehensive analysis of various polymers and biopolymers, such as polydopamine, chitosan, polyethylene glycol, polycaprolactone, alginate, gelatin, albumin, and others, is conducted to elucidate their advantages, benefits, and utilization across biomedical disciplines. Furthermore, this review extends its scope beyond polymerization and biomedical applications to encompass topics such as surface functionalization, chemical modification of MSNs, recent patents in the MSN domain, and the toxicity associated with MSN polymerization. Additionally, a brief discourse on green polymers is also included in review, highlighting their potential for fostering a sustainable future.

Monodispersed, Micron-Sized Supermicroporous Silica Particles by Cetyltrimethylammonium Bromide-Mediated Preparation

In this study, we present a novel modified Stöber method utilizing cetyltrimethylammonium bromide (CTAB) as a mediator for the preparation of monodispersed, micron-sized supermicroporous silica particles. Observed results show prepared silica particles ranging in size from 0.64 to 1.36 μm with an increase in CTAB concentration from 1.0 to 5.0 mM. The particles exhibited low polydispersity (<5%), a high Brunauer-Emmett-Teller surface area (570 to 1064 m2/g), and pore volumes ranging from 0.22 to 0.39 cm3/g. The pore size, determined using the Barrett-Joyner-Halenda method from the adsorption branches of the isotherms, was approximately 1.9 nm, specifically 1.83, 1.85, and 1.90 nm, as the CTAB concentration increased from 1.0 to 2.5 and 5.0 mM, respectively. The resulting particles displayed a narrow distribution of pore diameters. In addition, to obtain an in-depth understanding of the role of CTAB on the preparation of silica particles, a possible mechanism is also investigated using conductivity, dynamic light scattering (DLS), zeta potential, FT-IR spectra, and transmission electron microscopy. Our findings demonstrate that CTAB plays multiple roles in the hydrolysis/condensation of TEOS (tetraethyl orthosilicate) and subsequent nucleation and growth of silica particles. CTAB acts as a template for superporosity, a stabilizer for colloids, and an accelerator for nucleation and growth, leading to formation of monodispersed micrometer silica particles. Further characterization through FT-IR and 29Si solid NMR spectra revealed that the micron silica particles were obtained with inhomogeneity in the condensation degree, allowing for selective etching through hot incubation to form micron-sized hollow silica spheres.

Sustainable synthesis of multifunctional nanomaterials from rice wastes: a comprehensive review

More than 60% of India's population relies on agriculture as their primary source of income, making it the nation's most important economic sector. Rice husk (often abbreviated as RH) is one of the most typical by-products of agricultural production. Every five tonnes of rice that is harvested results in the production of one tonne of husk. The concept of recycling and reusing waste from agricultural production has received interest from a variety of environmental and industrial perspectives. A wide variety of nanomaterials, including nano-zeolite, nanocarbon, and nano-silica, have been discovered in agro-waste. From rice cultivation to the finished product, there was a by-product consisting of husk that comprised 20% of the overall weight, or RH. The percentage of silica in RH ash ranges from 60 to 40%, with the remaining percentage consisting of various minerals. As a direct consequence of this, several distinct approaches to generating and extracting nanomaterial from rice husk have been developed. Because it contains a significant amount of cellulose and lignin, RH is an excellent and economical source of carbon precursor. The goal of this chapter is to produce carbon-based nanomaterials from RH.

Improving the functionality of biodegradable food packaging materials via porous nanomaterials

Non-biodegradability and disposal problems are the major challenges associated with synthetic plastic packaging. This review article discusses a new generation of biodegradable active and smart packaging based on porous nanomaterials (PNMs), which maintains the quality and freshness of food products while meeting biodegradability requirements. PNMs have recently gained significant attention in the field of food packaging due to their large surface area, peculiar structures, functional flexibility, and thermal stability. We present for the first time the recently published literature on the incorporation of various PNMs into renewable materials to develop advanced, environmentally friendly, and high-quality packaging technology. Various emerging packaging technologies are discussed in this review, along with their advantages and disadvantages. Moreover, it provides general information about PNMs, their characterization, and fabrication methods. It also briefly describes the effects of different PNMs on the functionality of biopolymeric films. Furthermore, we examined how smart packaging loaded with PNMs can improve food shelf life and reduce food waste. The results indicate that PNMs play a critical role in improving the antimicrobial, thermal, physicochemical, and mechanical properties of natural packaging materials. These tailor-made materials can simultaneously extend the shelf life of food while reducing plastic usage and food waste.

pH-Responsive Biomaterials for the Treatment of Dental Caries-A Focussed and Critical Review

Dental caries is a common and costly multifactorial biofilm disease caused by cariogenic bacteria that ferment carbohydrates to lactic acid, demineralizing the inorganic component of teeth. Therefore, low pH (pH 4.5) is a characteristic signal of the localised carious environment, compared to a healthy oral pH range (6.8 to 7.4). The development of pH-responsive delivery systems that release antibacterial agents in response to low pH has gained attention as a targeted therapy for dental caries. Release is triggered by high levels of acidogenic species and their reduction may select for the establishment of health-associated biofilm communities. Moreover, drug efficacy can be amplified by the modification of the delivery system to target adhesion to the plaque biofilm to extend the retention time of antimicrobial agents in the oral cavity. In this review, recent developments of different pH-responsive nanocarriers and their biofilm targeting mechanisms are discussed. This review critically discusses the current state of the art and innovations in the development and use of smart delivery materials for dental caries treatment. The authors' views for the future of the field are also presented.

Mesoporous Materials as Elements of Modern Drug Delivery Systems for Anti-Inflammatory Agents: A Review of Recent Achievements

Interest in the use of mesoporous materials as carriers of medicinal substances has been steadily increasing in the last two decades. Mesoporous carriers have application in the preparation of delivery systems for drugs from various therapeutic groups; however, their use as the carriers of anti-inflammatory agents is particularly marked. This review article, with about 170 references, summarizes the achievements in the application of mesoporous materials as the carriers of anti-inflammatory agents in recent years. This article will discuss a variety of mesoporous carriers as well as the characteristics of their porous structure that determine further use of these materials in the field of medical applications. Special attention will be paid to the progress observed in the construction of stimuli-responsive drug carriers and systems providing site-specific drug delivery. Subsequently, a review of the literature devoted to the use of mesoporous matrices as the carriers of anti-inflammatory drugs was carried out.

Nanoarchitectured prototypes of mesoporous silica nanoparticles for innovative biomedical applications

Despite exceptional morphological and physicochemical attributes, mesoporous silica nanoparticles (MSNs) are often employed as carriers or vectors. Moreover, these conventional MSNs often suffer from various limitations in biomedicine, such as reduced drug encapsulation efficacy, deprived compatibility, and poor degradability, resulting in poor therapeutic outcomes. To address these limitations, several modifications have been corroborated to fabricating hierarchically-engineered MSNs in terms of tuning the pore sizes, modifying the surfaces, and engineering of siliceous networks. Interestingly, the further advancements of engineered MSNs lead to the generation of highly complex and nature-mimicking structures, such as Janus-type, multi-podal, and flower-like architectures, as well as streamlined tadpole-like nanomotors. In this review, we present explicit discussions relevant to these advanced hierarchical architectures in different fields of biomedicine, including drug delivery, bioimaging, tissue engineering, and miscellaneous applications, such as photoluminescence, artificial enzymes, peptide enrichment, DNA detection, and biosensing, among others. Initially, we give a brief overview of diverse, innovative stimuli-responsive (pH, light, ultrasound, and thermos)- and targeted drug delivery strategies, along with discussions on recent advancements in cancer immune therapy and applicability of advanced MSNs in other ailments related to cardiac, vascular, and nervous systems, as well as diabetes. Then, we provide initiatives taken so far in clinical translation of various silica-based materials and their scope towards clinical translation. Finally, we summarize the review with interesting perspectives on lessons learned in exploring the biomedical applications of advanced MSNs and further requirements to be explored.

Adsorption of lysozyme into a charged confining pore

Several applications arise from the confinement of proteins on surfaces because their stability and biological activity are enhanced. It is also known that the way in which a protein adsorbs on the surface is important for its biological function since its active sites should not be obstructed. In this study, the adsorption properties of hen egg-white lysozyme, HEWL, into a negatively charged silica pore is examined by employing a coarse-grained model and constant-pH Monte Carlo simulations. The role of electrostatic interactions is taken into account via including the Debye-Hückel potentials into the Cα structure-based model. We evaluate the effects of pH, salt concentration, and pore radius on the protein preferential orientation and spatial distribution of its residues regarding the pore surface. By mapping the residues that stay closer to the pore surface, we find that the increase of pH leads to orientational changes of the adsorbed protein when the solution pH gets closer to the HEWL isoelectric point. Under these conditions, the pK_a shift of these important residues caused by the adsorption into the charged confining surface results in a HEWL charge distribution that stabilizes the adsorption in the observed protein orientation. We compare our observations to the results of the pK_a shift for HEWL available in the literature and to some experimental data.

SBA-15 with Crystalline Walls Produced via Thermal Treatment with the Alkali and Alkali Earth Metal Ions

Crystalline walled SBA-15 with large pore size were prepared using alkali and alkali earth metal ions (Na⁺, Li⁺, K⁺ and Ca²⁺). For this work, the ratios of alkali metal ions (Si/metal ion) ranged from 2.1 to 80, while the temperatures tested ranged from 500 to 700 °C. The SBA-15 prepared with Si/Na⁺ ratios ranging from 2.1 to 40 at 700 °C exhibited both cristobalite and quartz SiO₂ structures in pore walls. When the Na⁺ amount increased (i.e., Si/Na increased from 80 to 40), the pore size was increased remarkably but the surface area and pore volume of the metal ion-based SBA-15 were decreased. When the SBA-15 prepared with Li⁺, K⁺ and Ca²⁺ ions (Si/metal ion = 40) was thermally treated at 700 °C, the crystalline SiO₂ of quartz structure with large pore diameter (i.e., 802.5 Å) was observed for Ca⁺² ion-based SBA-15, while no crystalline SiO₂ structures were observed in pore walls for both the K⁺ and Li⁺ ions treated SBA-15. The crystalline SiO₂ structures may be formed by the rearrangement of silica matrix when alkali or alkali earth metal ions are inserted into silica matrix at elevated temperature.

Kidney-Protector Lipidic Cilastatin Derivatives as Structure-Directing Agents for the Synthesis of Mesoporous Silica Nanoparticles for Drug Delivery

Mesoporous silica nanomaterials have emerged as promising vehicles in controlled drug delivery systems due to their ability to selectively transport, protect, and release pharmaceuticals in a controlled and sustained manner. One drawback of these drug delivery systems is their preparation procedure that usually requires several steps including the removal of the structure-directing agent (surfactant) and the later loading of the drug into the porous structure. Herein, we describe the preparation of mesoporous silica nanoparticles, as drug delivery systems from structure-directing agents based on the kidney-protector drug cilastatin in a simple, fast, and one-step process. The concept of drug-structure-directing agent (DSDA) allows the use of lipidic derivatives of cilastatin to direct the successful formation of mesoporous silica nanoparticles (MSNs). The inherent pharmacological activity of the surfactant DSDA cilastatin-based template permits that the MSNs can be directly employed as drug delivery nanocarriers, without the need of extra steps. MSNs thus synthesized have shown good sphericity and remarkable textural properties. The size of the nanoparticles can be adjusted by simply selecting the stirring speed, time, and aging temperature during the synthesis procedure. Moreover, the release experiments performed on these materials afforded a slow and sustained drug release over several days, which illustrates the MSNs potential utility as drug delivery system for the cilastatin cargo kidney protector. While most nanotechnology strategies focused on combating the different illnesses this methodology emphasizes on reducing the kidney toxicity associated to cancer chemotherapy.

An Update on Mesoporous Silica Nanoparticle Applications in Nanomedicine

The efficient and safe delivery of therapeutic drugs, proteins, and nucleic acids are essential for meaningful therapeutic benefits. The field of nanomedicine shows promising implications in the development of therapeutics by delivering diagnostic and therapeutic compounds. Nanomedicine development has led to significant advances in the design and engineering of nanocarrier systems with supra-molecular structures. Smart mesoporous silica nanoparticles (MSNs), with excellent biocompatibility, tunable physicochemical properties, and site-specific functionalization, offer efficient and high loading capacity as well as robust and targeted delivery of a variety of payloads in a controlled fashion. Such unique nanocarriers should have great potential for challenging biomedical applications, such as tissue engineering, bioimaging techniques, stem cell research, and cancer therapies. However, in vivo applications of these nanocarriers should be further validated before clinical translation. To this end, this review begins with a brief introduction of MSNs properties, targeted drug delivery, and controlled release with a particular emphasis on their most recent diagnostic and therapeutic applications.

New Trends in the Use of Volatile Compounds in Food Packaging

In the last years, many of the research studies in the packaging industry have been focused on food active packaging in order to develop new materials capable of retaining the active agent in the polymeric matrix and controlling its release into food, which is not easy in many cases due to the high volatility of the chemical compounds, as well as their ease of diffusion within polymeric matrices. This review presents a complete revision of the studies that have been carried out on the incorporation of volatile compounds to food packaging applications. We provide an overview of the type of volatile compounds used in active food packaging and the most recent trends in the strategies used to incorporate them into different polymeric matrices. Moreover, a thorough discussion regarding the main factors affecting the retention capacity and controlled release of volatile compounds from active food packaging is presented.

A Review of Composite Phase Change Materials Based on Porous Silica Nanomaterials for Latent Heat Storage Applications

Phase change materials (PCMs) can store thermal energy as latent heat through phase transitions. PCMs using the solid-liquid phase transition offer high 100-300 J g-1 enthalpy at constant temperature. However, pure compounds suffer from leakage, incongruent melting and crystallization, phase separation, and supercooling, which limit their heat storage capacity and reliability during multiple heating-cooling cycles. An appropriate approach to mitigating these drawbacks is the construction of composites as shape-stabilized phase change materials which retain their macroscopic solid shape even at temperatures above the melting point of the active heat storage compound. Shape-stabilized materials can be obtained by PCMs impregnation into porous matrices. Porous silica nanomaterials are promising matrices due to their high porosity and adsorption capacity, chemical and thermal stability and possibility of changing their structure through chemical synthesis. This review offers a first in-depth look at the various methods for obtaining composite PCMs using porous silica nanomaterials, their properties, and applications. The synthesis and properties of porous silica composites are presented based on the main classes of compounds which can act as heat storage materials (paraffins, fatty acids, polymers, small organic molecules, hydrated salts, molten salts and metals). The physico-chemical phenomena arising from the nanoconfinement of phase change materials into the silica pores are discussed from both theoretical and practical standpoints. The lessons learned so far in designing efficient composite PCMs using porous silica matrices are presented, as well as the future perspectives on improving the heat storage materials.

Nanoarchitecting Hierarchical Mesoporous Siliceous Frameworks: A New Way Forward

Owing to their attractive physicochemical and morphological attributes, mesoporous silica nanoparticles (MSNs) have attracted increasing attention over the past two decades for their utilization in diversified fields. Despite the success, these highly stable siliceous frameworks often suffer from several shortcomings of compatibility issues, uncontrollable degradability leading to long-term retention in vivo, and substantial unpredictable toxicity risks, as well as deprived drug encapsulation efficiency, which could limit their applicability in medicine. Along this line, various advancements have been made in re-engineering the stable siliceous frameworks, such as the incorporation of diverse molecular organic, as well as inorganic (cationic and anionic) species and monitoring the processing, as well as formulation parameters, resulting in the hetero-nanostructures of irregular-shaped (Janus and multi-podal) and dynamically-modulated (deformable solids) architectures with high morphological complexity. Insightfully, this review gives a brief emphasis on re-engineering such stable siliceous frameworks through modifying their intrinsic structural and physicochemical attributes. In conclusion, we recapitulate the review with exciting perspectives.

A multifunctional CeO2@SiO2-PEG nanoparticle carrier for delivery of food derived proanthocyanidin and curcumin as effective antioxidant, neuroprotective and anticancer agent

The nanoparticle systems could effectively overcome the drug delivery challenges of food bioactive compounds. In this study, a novel and effective multifunctional PEG modified CeO₂@SiO₂ nanoparticle (CSP-NPs) system was successfully fabricated. Food derived proanthocyanidin (PAC) and curcumin (Cur) were loaded onto CSP-NPs and formed as PAC-NPs and Cur-NPs. Fourier transform Infrared spectra, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and dynamic light scattering were used to characterize the prepared NPs. CSP-NPs, PAC-NPs and Cur-NPs displayed spherical shape with about 35-45 nm size. The bioactivity analysis revealed that CSP-NPs system could effectively deliver PAC and Cur to exhibit strong antioxidant activity, potent neuroprotective effect against Aβ_1-42-mediated toxicity in PC-12 cells (recovered cell viability from 57.5% to 81.0% at the dose of 25 μg/mL) and effective antiproliferative effects on HepG2 and Hela cells. Besides, all prepared nanoparticles (0-100 µg/ml) used in this study showed no significant toxicity on cell models of antioxidative and neuroprotective activities, excepting for cancer cells, suggesting that these nanoparticles had the potential of being utilized in drug delivery. Therefore, CSP-NPs might be a promising delivery system for hydrophilic molecule proanthocyanidin and hydrophobic molecule curcumin against the oxidative damage, neurodegenerative diseases and cancer, which could facilitate the application of food derived nutrients in functional foods industry.

Effect of Confinement in Nanopores on RNA Interactions with Functionalized Mesoporous Silica Nanoparticles

Amine-functionalized mesoporous silica nanoparticles (MSNPAs) are ideal carriers for oligonucleotides for gene delivery and RNA interference. This investigation examines the thermodynamic driving force of interactions of double-stranded (ds) RNA with MSNPAs as a function of RNA length (84 and 282 base pair) and particle pore diameter (nonporous, 2.7, 4.3, and 8.1 nm) using isothermal titration calorimetry, extending knowledge of solution-based nucleic acid-polycation interactions to RNA confined in nanopores. Adsorption of RNA follows a two-step process: endothermic interactions driven by entropic contribution from counterion (and water) release and an exothermic regime dominated by short-range interactions within the pores. Evidence of hindered pore loading of the longer RNA and pore size-dependent confinement of RNA in the MSPAs is provided from the relative contributions of the endothermic and exothermic regimes. Reduction of endothermic and exothermic enthalpies in both regimes in the presence of salt for both lengths of RNA indicates the significant contribution of short-range electrostatic interactions, whereas ΔH and ΔG values are consistent with conformation changes and desolvation of nucleic acids upon binding with polycations. Knowledge of the interactions between RNA and functionalized porous nanoparticles will aid in porous nanocarrier design suitable for functional RNA delivery.

Mesoporous Silica Nanoparticles in Bioimaging

A biomedical contrast agent serves to enhance the visualisation of a specific (potentially targeted) physiological region. In recent years, mesoporous silica nanoparticles (MSNs) have developed as a flexible imaging platform of tuneable size/morphology, abundant surface chemistry, biocompatibility and otherwise useful physiochemical properties. This review discusses MSN structural types and synthetic strategies, as well as methods for surface functionalisation. Recent applications in biomedical imaging are then discussed, with a specific emphasis on magnetic resonance and optical modes together with utility in multimodal imaging.

Naturally Occurring and Synthetic Mesoporous Nanosilica: Multimodal Applications in Frontier Areas of Science

Mesoporous silica nanoparticles (MSNs) have gained attention worldwide due to their structural versatility for diverse applications in a number of frontier areas of sciences. The intrinsic chemical, textural and structural features of MSNs allow fabricating versatile multifunctional nanosystems. The present review provides an overview of the research progress in artificial and biological production of MSNs, their properties and various applications in cutting edge areas of sciences.

Ultrasound responsive mesoporous silica nanoparticles for biomedical applications

Nanotechnology, which has already revolutionised many technological areas, is expected to transform life sciences. In this sense, nanomedicine could address some of the most important limitations of conventional medicine. In general, nanomedicine includes three major objectives: (1) trap and protect a great amount of therapeutic agents; (2) carry them to the specific site of disease avoiding any leakage; and (3) release on-demand high local concentrations of therapeutic agents. This feature article will make special emphasis on mesoporous silica nanoparticles that release their therapeutic cargo in response to ultrasound.

Stimuli-Responsive Nanomachines and Caps for Drug Delivery

In this review we focus on methods that are used to trap and release on command therapeutic drugs from mesoporous silica nanoparticles (MSNs). The pores in the MSNs are large enough to accommodate a wide range of cargo molecules such as anticancer and antibiotic drugs and yet small enough to be blocked by a variety of bulky molecules that act as caps. The caps are designed to be tightly attached to the pore openings and trap the cargo molecules without leakage, but upon application of a designed stimulus detach from the nanoparticles and release the cargo. Of special emphasis in this review are nanomachines that respond to stimuli administered from external sources such as light or magnetic fields, or from chemical stimuli produced by the biological system such as a general change in pH or redox potential, or a highly specific chemical produced by a cancer cell or infectious bacterium. The goal is to release a high local concentration of the cargo only where and when it is needed, thus minimizing off-target side effects. We discuss sophisticated reversible nanomachines but also discuss some useful caps that simply break off from the nanoparticles in response to the selected stimulus. Many ingenious systems have been and are being designed; we primarily highlight those that have been demonstrated to operate in vitro and/or in vivo. In most cases the closed MSNs are endocytosed by diseased or infected cells and opened inside the cells to release the drugs. We begin with an overview of the nanoparticles and nanomachines and then present examples of drug release triggered by internal chemical stimuli from the organism and finally by external light and magnetic field stimuli.

Mesoporous Silica Nanoparticles: A Comprehensive Review on Synthesis and Recent Advances

Recent advancements in drug delivery technologies utilizing a variety of carriers have resulted in a path-breaking revolution in the approach towards diagnosis and therapy alike in the current times. Need for materials with high thermal, chemical and mechanical properties have led to the development of mesoporous silica nanoparticles (MSNs). These ordered porous materials have garnered immense attention as drug carriers owing to their distinctive features over the others. They can be synthesized using a relatively simple process, thus making it cost effective. Moreover, by controlling the parameters during the synthesis; the morphology, pore size and volume and particle size can be transformed accordingly. Over the last few years, a rapid increase in research on MSNs as drug carriers for the treatment of various diseases has been observed indicating its potential benefits in drug delivery. Their widespread application for the loading of small molecules as well as macromolecules such as proteins, siRNA and so forth, has made it a versatile carrier. In the recent times, researchers have sorted to several modifications in the framework of MSNs to explore its potential in drug resistant chemotherapy, antimicrobial therapy. In this review, we have discussed the synthesis of these multitalented nanoparticles and the factors influencing the size and morphology of this wonder carrier. The second part of this review emphasizes on the applications and the advances made in the MSNs to broaden the spectrum of its use especially in the field of biomedicine. We have also touched upon the lacunae in the thorough understanding of its interaction with a biological system which poses a major hurdle in the passage of this carrier to the clinical level. In the final part of this review, we have discussed some of the major patents filed in the field of MSNs for therapeutic purpose.

Do the fragments from decomposed ZIF-8 greatly affect some of the intramolecular proton-transfer of thymine? A quantum chemical study

The intramolecular proton-transfer processes of thymine were investigated by the density functional theory method. It is shown that the mutation from keto (T) to enol (T′) form is affected by zeolitic imidazolate framework-8 (ZIF-8) fragments such as single 2-methylimidazole neutral crystals (M), and negatively charged 2-methylimidazole ligands (M⁻). Results show that with the number (n) of water (w) molecules that assist proton-transfer increasing from 1 to 4, the order of the tautomeric energy barriers (in kcal mol⁻¹) is T-2w (16.3) < T-1w (17.6) < T-3w (17.8) < T-4w (20.5). In the presence of M, the order of energy barrier is MT-2w (16.6) < MT-1w (17.7) < MT-3w (18.9) < MT-4w (20.8). M⁻ has a catalysis effect on the energy barrier and the order is M⁻T-2w (14.4) < M⁻T-3w (15.2) < M⁻T-1w (16.3) < M⁻T-4w (16.8). The attachment of the M⁻ fragment slightly promotes the proton-transfer processes in some instances. The characterization of the proton-transfer processes is helpful to understand the genotoxicity of ZIF-8 during drug delivery applications.

Investigations on whether fragments from decomposed ZIF-8 would affect the intramolecular proton-transfer of thymine by DFT modeling.

Adsorption and release of ampicillin antibiotic from ordered mesoporous silica

In this work the adsorption and the release of ampicillin - a β-lactam penicillin-like antibiotic - from MCM-41, SBA-15, and (amino functionalized) SBA-15-NH₂ ordered mesoporous silica (OMS) materials were investigated. The silica matrices differ for their pore size (SBA-15 vs. MCM-41) mainly, and also for surface charge (SBA-15 and MCM-41, vs. SBA-15-NH₂). OMS samples were characterized through small-angle X-rays scattering (SAXS), transmission electron microscopy (TEM), N₂ adsorption-desorption isotherms, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and potentiometric titrations. The quantification of immobilized and released ampicillin was monitored by mean of UV-Vis spectroscopy. Experimental adsorption isotherms evidenced that ampicillin's loading is not related to the pore size (d_BJH) of the adsorbent. Indeed the maximal loadings were 237mg/g for SBA-15 (d_BJH=6.5nm), 278mg/g for MCM-41 (d_BJH=2.2nm), and 333mg/g for SBA-15-NH₂ (d_BJH=5.6nm). Loading seems, instead, to be related to the surface charge density (σ) of the sorbent surface. Indeed, at pH 7.4 ampicillin drug is negatively charged and likely prefers to interact with SBA-15-NH₂ (σ_SBA-15-NH2=+0.223Cm^-2) rather than the slightly negatively charged silicas (σ_SBA-15=-0.044Cm^-2 and σ_MCM-41=-0.033Cm^-2). Similarly, ampicillin release is affected by interfacial interactions. Indeed, we found a burst release from pure silica samples (SBA-15 and MCM-41), whereas a sustained one from SBA-15-NH₂ sample. We explain this behavior as a result of an attractive interaction between the protonated amino group of SBA-15-NH₂ and the negatively charged carboxylate group of ampicillin. In summary, in order to obtain a sustained drug release, the chemical nature of the matrix's surface plays a role which is more important than its textural features. SBA-15-NH₂ matrix is hence a suitable candidate for local sustained release of antibiotic drugs.

Grafted Polymethylhydrosiloxane on Hierarchically Porous Silica Monoliths: A New Path to Monolith-Supported Palladium Nanoparticles for Continuous Flow Catalysis Applications

Polymethylhydrosiloxane has been grafted on the surface of a hierarchically porous silica monolith using a facile catalytic reaction between Si-H and silanol to anchor the polymer. This easy methodology leads to the functionalization of the surface of a silica monolith, where a large amount of free Si-H bonds remain available for reducing metal ions in solution. Palladium nanoparticles of 15 nm have been synthesized homogeneously inside the mesopores of the monolith without any stabilizers, using a flow of a solution containing Pd²⁺. This monolith was used as column-type fixed bed catalyst for continuous flow hydrogenation of styrene and selective hydrogenation of 3-hexyn-1-ol, in each case without a significant decrease of the catalytic activity after several hours or days. Conversion, selectivity, and stereoselectivity of the alkyne hydrogenation can be tuned by flow rates of hydrogen and the substrate solution, leading to high productivity (1.57 mol g(Pd)^-1 h^-1) of the corresponding cis-alkene.

Surface modification of a polyvinyl alcohol sponge with functionalized boronic acids to develop porous materials for multicolor emission, chemical sensing and 3D cell culture

Surface modification of a polyvinyl alcohol sponge with functionalized boronic acids led to the formation of porous materials applicable for multicolor emission, chemical sensing and 3D cell culture.

Water-soluble photoluminescent fullerene capped mesoporous silica for pH-responsive drug delivery and bioimaging

In this paper, a biocompatible and water-soluble fluorescent fullerene (C₆₀-TEG-COOH) coated mesoporous silica nanoparticle (MSN) was successfully fabricated for pH-sensitive drug release and fluorescent cell imaging. The MSN was first reacted with 3-aminopropyltriethoxysilane to obtain an amino-modified MSN, and then the water-soluble C₆₀ with a carboxyl group was used to cover the surface of the MSN through electrostatic interaction with the amino group in PBS solution (pH = 7.4). The release of doxorubicin hydrochloride (DOX) could be triggered under a mild acidic environment (lysosome, pH = 5.0) due to the protonation of C₆₀-TEG-COO^-, which induced the dissociation of the C₆₀-TEG-COOH modified MSN (MSN@C₆₀). Furthermore, the uptake of nanoparticles by cells could be tracked because of the green fluorescent property of the C₆₀-modified MSN. In an in vitro study, the prepared materials showed excellent biocompatibility and the DOX-loaded nanocarrier exhibited efficient anticancer ability. This work offered a simple method for designing a simultaneous pH-responsive drug delivery and bioimaging system.

A slowing down of proton motion from HPTS to water adsorbed on the MCM-41 surface

We report on the steady-state and femtosecond-nanosecond (fs-ns) behaviour of 8-hydroxypyrene-1,3,6-trisulfonate (pyranine, HPTS) and its interaction with mesoporous silica based materials (MCM-41) in both solid-state and dichloromethane (DCM) suspensions in the absence and presence of water. In the absence of water, HPTS forms aggregates which are characterized by a broad emission spectrum and multiexponential behavior (τsolid-state/DCM = 120 ps, 600 ps, 2.2 ns). Upon interaction with MCM41, the aggregate population is found to be lower, leading to the formation of adsorbed monomers. In the presence of water (1%), HPTS with and without MCM41 materials in DCM suspensions undergoes an excited-state intermolecular proton-transfer (ESPT) reaction in the protonated form (ROH*) producing a deprotonated species (RO(-)*). The long-time emission decays of the ROH* in different systems in the presence of water are multiexponential, and are analysed using the diffusion-assisted geminate recombination model. The obtained proton-transfer and recombination rate constants for HPTS and HPTS/MCM41 complexes in DCM suspensions in the presence of water are kPT = 13 ns(-1), krec = 7.5 Å ns(-1), and kPT = 5.4 ns(-1), krec = 2.2 Å ns(-1), respectively, The slowing down of both processes in the latter case is explained in terms of specific interactions of the dye and of the water molecules with the silica surface. The ultrafast dynamics (fs-regime) of the HPTS/MCM41 complexes in DCM suspensions, without and with water, shows two components which are assigned to intramolecular vibrational-energy relaxation (IVR) (∼120 fs vs. ∼0.8 ps), and vibrational relaxation/cooling (VC), and charge transfer (CT) processes (∼2 ps without water and ∼5 ps with water) of the adsorbed ROH*. Our results provide new knowledge on the interactions and the proton-transfer reaction dynamics of HPTS adsorbed on mesoporous materials.

Hierarchical mesoporous silica nanoparticles for tailorable drug release

In order to modulate the drug release profiles, the hierarchical mesoporous silica nanoparticles (HMSNs) are fabricated by a two-step synthetic process. The HMSNs exhibit uniform spherical morphology with nanoscaled size, well mono-dispersed size distribution, and smooth surface. Because of the hierarchical pore structures with different mesoporous sizes and morphologies (partial open and partial blocked pores), the HMSNs can release the loaded drug in a controlled manner. The hierarchical mesoporous structures directed drug release profiles suggest a feasible strategy to tailor drug release behaviors. Meanwhile, the HMSNs exhibit good biocompatibility. Therefore, the HMSNs having tailorable drug release capacity would be a potential candidate to improve their therapeutic efficiency for drug delivery systems.

Stimuli-responsive nanogel composites and their application in nanomedicine

Nanogels are nanosized crosslinked polymer networks capable of absorbing large quantities of water. Specifically, smart nanogels are interesting because of their ability to respond to biomedically relevant changes like pH, temperature, etc. In the last few decades, hybrid nanogels or composites have been developed to overcome the ever increasing demand for new materials in this field. In this context, a hybrid refers to nanogels combined with different polymers and/or with nanoparticles such as plasmonic, magnetic, and carbonaceous nanoparticles, among others. Research activities are focused nowadays on using multifunctional hybrid nanogels in nanomedicine, not only as drug carriers but also as imaging and theranostic agents. In this review, we will describe nanogels, particularly in the form of composites or hybrids applied in nanomedicine.

Cellulose conjugated FITC-labelled mesoporous silica nanoparticles: intracellular accumulation and stimuli responsive doxorubicin release

Herein, we design novel cellulose conjugated mesoporous silica nanoparticle (CLS-MSP) based nanotherapeutics for stimuli responsive intracellular doxorubicin (DOX) delivery. DOX molecules are entrapped in pores of the fabricated mesoporous silica nanoparticles (MSPs) while cellulose is used as an encapsulating material through esterification on the outlet of the pores of the MSPs to avoid premature DOX release under physiological conditions. In in vitro studies, stimuli responsive DOX release is successfully achieved from DOX loaded cellulose conjugated mesoporous silica nanoparticles (DOX/CLS-MSPs) by pH and cellulase triggers. Intracellular accumulation of DOX/CLS-MSPs in human liver cancer cells (HepG2 cells) is investigated through confocal microscope magnification. Cell viability of HepG2 cells is determined as the percentage of the cells incubated with DOX/CLS-MSPs compared with that of non-incubated cells through an MTT assay.

Interfacial processes that modulate the kinetics of lipase-mediated catalysis using porous silica host particles

Surface immobilised lipases are important bioactive materials that have a wide range of applications in the biotechnology, chemical and pharmaceutical industries.

pH-responsive release of chlorhexidine from modified nanoporous silica nanoparticles for dental applications

A pH-sensitive stimulus-response system for controlled drug release was prepared by modifying nanoporous silica nanoparticles (NPSNPs) with poly(4-vinylpyridine) using a bismaleimide as linker. At physiological pH values, the polymer serves as gate keeper blocking the pore openings to prevent the release of cargo molecules. At acidic pH values as they can occur during a bacterial infection, the polymer strains become protonated and straighten up due to electrostatic repulsion. The pores are opened and the cargo is released. The drug chlorhexidine was loaded into the pores because of its excellent antibacterial properties and low tendency to form resistances. The release was performed in PBS and diluted hydrochloric acid, respectively. The results showed a considerably higher release in acidic media compared to neutral solvents. Reversibility of this pH-dependent release was established. In vitro tests proved good cytocompatibility of the prepared nanoparticles. Antibacterial activity tests with

Implications for blood-brain-barrier permeability, in vitro oxidative stress and neurotoxicity potential induced by mesoporous silica nanoparticles: effects of surface modification

MSNs are shown to have the potential to overcome the BBB and cause neuronal damage. However, the neurotoxicity potential could be mediated with surface modification.

Preparation of polyetheretherketone composites with nanohydroxyapatite rods and carbon nanofibers having high strength, good biocompatibility and excellent thermal stability

The WST-1 assay shows that the PEEK/15 vol% nHA–1.9 vol% CNF hybrid composite has excellent biocompatibility.

Recent Advance on Mesoporous Silica Nanoparticles-Based Controlled Release System: Intelligent Switches Open up New Horizon

Mesoporous silica nanoparticle (MSN)-based intelligent transport systems have attracted many researchers' attention due to the characteristics of uniform pore and particle size distribution, good biocompatibility, high surface area, and versatile functionalization, which have led to their widespread application in diverse areas. In the past two decades, many kinds of smart controlled release systems were prepared with the development of brilliant nano-switches. This article reviews and discusses the advantages of MSN-based controlled release systems. Meanwhile, the switching mechanisms based on different types of stimulus response are systematically analyzed and summarized. Additionally, the application fields of these devices are further discussed. Obviously, the recent evolution of smart nano-switches promoted the upgrading of the controlled release system from the simple "separated" switch to the reversible, multifunctional, complicated logical switches and selective switches. Especially the free-blockage switches, which are based on hydrophobic/hydrophilic conversion, have been proposed and designed in the last two years. The prospects and directions of this research field are also briefly addressed, which could be better used to promote the further development of this field to meet the needs of mankind.

Towards efficient chemical synthesis via engineering enzyme catalysis in biomimetic nanoreactors

Biocatalysis with immobilized enzymes as catalysts holds enormous promise in developing more efficient and sustainable processes for the synthesis of fine chemicals, chiral pharmaceuticals and biomass feedstocks. Despite the appealing potentials, nowadays the industrial-scale application of biocatalysts is still quite modest in comparison with that of traditional chemical catalysts. A critical issue is that the catalytic performance of enzymes, the sophisticated and vulnerable catalytic machineries, strongly depends on their intracellular working environment; however the working circumstances provided by the support matrix are radically different from those in cells. This often leads to various adverse consequences on enzyme conformation and dynamic properties, consequently decreasing the overall performance of immobilized enzymes with regard to their activity, selectivity and stability. Engineering enzyme catalysis in support nanopores by mimicking the physiological milieu of enzymes in vivo and investigating how the interior microenvironment of nanopores imposes an influence on enzyme behaviors in vitro are of paramount significance to modify and improve the catalytic functions of immobilized enzymes. In this feature article, we have summarized the recent advances in mimicking the working environment and working patterns of intracellular enzymes in nanopores of mesoporous silica-based supports. Especially, we have demonstrated that incorporation of polymers into silica nanopores could be a valuable approach to create the biomimetic microenvironment for enzymes in the immobilized state.