A facile route for rapid synthesis of hollow mesoporous silica nanoparticles as pH-responsive delivery carrier

Design strategies, surface functionalization, and environmental remediation potentialities of polymer-functionalized nanocomposites

Inorganic nanoparticles (NPs) have a tunable shape, size, surface morphology, and unique physical properties like catalytic, magnetic, electronic, and optical capabilities. Unlike inorganic nanomaterials, organic polymers exhibit excellent stability, biocompatibility, and processability with a tailored response to external stimuli, including pH, heat, light, and degradation properties. Nano-sized assemblies derived from inorganic and polymeric NPs are combined in a functionalized composite form to import high strength and synergistically promising features not reflected in their part as a single constituent. These new properties of polymer/inorganic functionalized materials have led to emerging applications in a variety of fields, such as environmental remediation, drug delivery, and imaging. This review spotlights recent advances in the design and construction of polymer/inorganic functionalized materials with improved attributes compared to single inorganic and polymeric materials for environmental sustainability. Following an introduction, a comprehensive review of the design and potential applications of polymer/inorganic materials for removing organic pollutants and heavy metals from wastewater is presented. We have offered valuable suggestions for piloting, and scaling-up polymer functionalized nanomaterials using simple concepts. This review is wrapped up with a discussion of perspectives on future research in the field.

Functionalization of Nanoparticulate Drug Delivery Systems and Its Influence in Cancer Therapy

Research into the application of nanocarriers in the delivery of cancer-fighting drugs has been a promising research area for decades. On the other hand, their cytotoxic effects on cells, low uptake efficiency, and therapeutic resistance have limited their therapeutic use. However, the urgency of pressing healthcare needs has resulted in the functionalization of nanoparticles' (NPs) physicochemical properties to improve clinical outcomes of new, old, and repurposed drugs. This article reviews recent research on methods for targeting functionalized nanoparticles to the tumor microenvironment (TME). Additionally, the use of relevant engineering techniques for surface functionalization of nanocarriers (liposomes, dendrimers, and mesoporous silica) and their critical roles in overcoming the current limitations in cancer therapy-targeting ligands used for targeted delivery, stimuli strategies, and multifunctional nanoparticles-were all reviewed. The limitations and future perspectives of functionalized nanoparticles were also finally discussed. Using relevant keywords, published scientific literature from all credible sources was retrieved. A quick search of the literature yielded almost 400 publications. The subject matter of this review was addressed adequately using an inclusion/exclusion criterion. The content of this review provides a reasonable basis for further studies to fully exploit the potential of these nanoparticles in cancer therapy.

Preparation and in-vitro evaluation of mesoporous biogenic silica nanoparticles obtained from rice and wheat husk as a biocompatible carrier for anti-cancer drug delivery

In this study, mesoporous silica nanocarriers were synthesized from natural sources such as rice and wheat husk for drug delivery application. First, the biogenic silica in cereals husk was extracted by acid leaching and then converted to sodium silicate as a silica precursor. Mesoporous silica nanoparticles were then synthesized by adding sodium silicate to the template mixture by continuous and discrete modes during the sol-gel process. The effects of natural sources type and precursor addition method on nanocarriers' morphological and physicochemical properties were investigated by XRD, FT-IR, BET and SEM analysis. Our results showed rice husk-based spherical nanocarriers were more crystalline with slit-shaped pores, while wheat husk-based nanocarriers had been composed of spherical nanoparticles with narrow cylindrical pores. The results also showed that by adding the precursor discretely, their hydrophilicity, particle size and pore size increased compared with the continuous mode, probably due to the high initial concentration of the precursor in the reaction mixture. Doxorubicin (Dox), as a model anticancer drug was loaded into the nanocarriers, and the drug release behavior was studied at two different pH values (7.4 and 5.4). In general, the accumulated released drug at pH 5.4 was approximately twice as much as pH 7.4 due to the higher solubility of doxorubicin at acidic environment. Also, the accumulated released drug at pH 5.4 for nanocarriers which had been synthesized by discrete mode, was higher than continuous mode, due to the larger pore diameter of them. The biocompatibility and cytotoxicity of nanocarriers and Dox-loaded nanocarriers were also investigated on the HFF-2 and MCF-7 cell lines, respectively. Moreover, apoptosis, as the mechanism of cell death, was evaluated by morphological study of the MCF-7 cells. Within acceptable toxicity limits and apoptosis induction, the Dox-loaded nanocarriers, especially discrete mode synthesized nanocarriers, exhibited high-efficiency anticancer effect on the MCF-7 cell line.

Low cost and scalable method for modifying surfaces of hollow particles from hydrophilic to hydrophobic

Hydrophobic hollow silica particles are desirable for several applications such as hydrophobic coatings, thermal insulation, and thermally resistant insulative paints. However, converting hydrophilic particles into hydrophobic particles without compromising their structural integrity is challenging. In this work, we present a low cost strategy to modify the surface of hollow silica particles from hydrophilic to hydrophobic without compromising their structural integrity.

Hybrid hollow silica particles: synthesis and comparison of properties with pristine particles

In the past decade, interest in hollow silica particles has grown tremendously because of their applications in diverse fields such as thermal insulation, drug delivery, battery cathodes, catalysis, and functional coatings. Herein, we demonstrate a strategy to synthesize hybrid hollow silica particles having shells made of either polymer-silica or carbon-silica. Hybrid shells were characterized using electron microscopy. The effect of hybrid shell type on particle properties such as thermal and moisture absorption was also investigated.

pH-Triggered Drug Release Controlled by Poly(Styrene Sulfonate) Growth Hollow Mesoporous Silica Nanoparticles

In the current report, hollow mesoporous silica (HMS) nanoparticles were successfully prepared by means of a hard-templating method and further modified with poly(styrene sulfonate) (PSS) via radical polymerization. Structural analysis, surface spectroscopy, and thermogravimetric characterization confirmed a successful surface modification of HMS nanoparticles. A hairy PSS was clearly visualized by high-resolution transmission electron microscopy measurement, and it is grown on the surface of HMS nanoparticles. The Brunauer-Emmett-Teller surface area and average pore size of HMS nanoparticles were reduced after surface modification because of the pore-blocking effect, which indicated that the PSS lies on the surface of nanoparticles. Nevertheless, the PSS acts as a "nano-gate" to control the release of curcumin which is triggered by pH. The drug-release profile of unmodified HMS nanoparticles showed a stormed release in both pH 7.4 and 5.0 of phosphate buffer saline buffer solution. However, a slow release (9.92% of cumulative release) of curcumin was observed at pH 7.4 when the surface of HMS nanoparticles was modified by PSS. The kinetic release study showed that the curcumin release mechanism from PSS@HMS nanoparticles followed the Ritger-Peppas kinetic model, which is the non-Fickian diffusion. Therefore, the PSS-decorated HMS nanoparticles demonstrate potential for pH-triggered drug release transport.

Fabrication of Ir-CoOx@mesoporous SiO2 Nanoreactors for Selective Hydrogenation of Substituted Nitroaromatics

Nanosized Ir catalysts suffer from serious side reactions and poor stability during hydrogenation of substituted nitroaromatics to produce aromatic amines. In this work, core-shell nanostructures with sub-4 nm Ir-CoO_x hybrid cores and mesoporous SiO₂ shells were designed and prepared to overcome these problems. The Ir-CoO_x hybrid cores were converted from IrCo alloy nanoparticles (NPs) inside SiO₂ through in situ calcination and reduction pretreatments. The SiO₂ mesoporous shells in Ir-CoO_x@SiO₂ nanoreactors prevented the agglomeration/sintering of IrCo NPs, while allowing the free reactants and products (big molecules). The synergy between Ir and CoO_x species improved H₂ adsorption, thus affecting the reaction rate as well as the selectivity to aromatic amines. As a result, the obtained Ir-CoO_x@SiO₂ nanocatalyst showed tremendous improvement in catalytic activity, selectivity, and stability.

Functionalized mesoporous silica nanoparticles and biomedical applications

Since the first report in early 1990s, mesoporous silica nanoparticles (MSNs) have progressively attracted the attention of scientists due to their potential applications in physic, energy storage, imaging, and especially in biomedical engineering. Owning the unique physiochemical properties, such as highly porosity, large surface area and pore volume, functionalizable, tunable pore and particle sizes and biocompatibility, and high loading cavity, MSNs offer efficient encapsulation and then controlled release, and in some cases, intracellular delivery of bioactive molecules for biomedical applications. During the last decade, functionalized MSNs that show respond upon the surrounding stimulus changes, such as temperature, pH, redox, light, ultrasound, magnetic or electric fields, enzyme, redox, ROS, glucose, and ATP, or their combinations, have continuously revolutionized their potential applications in biomedical engineering. Therefore, this review focuses on discussion the recent fabrication of functionalized MSNs and their potential applications in drug delivery, therapeutic treatments, diagnostic imaging, and biocatalyst. In addition, some potential clinical applications and challenges will also be discussed.

Integrating in situ formation of nanozymes with three-dimensional dendritic mesoporous silica nanospheres for hypoxia-overcoming photodynamic therapy

Despite great progress in photodynamic therapy (PDT), the therapeutic effect is still limited by some points, such as tumor hypoxia, the short lifetime and the limited action region of 1O2. Herein, a special kind of three-dimensional dendritic mesoporous silica nanosphere (3D-dendritic MSN) was synthesized and used as a robust nanocarrier to deliver abundant hydrophobic photosensitizer chlorin e6 (Ce6) to the A549 lung cancer cells. To address the tumor hypoxia issue, the nanozyme Pt nanoparticles (Pt NPs) were immobilized onto the channels of 3D-dendritic MSNs to catalyze the conversion of intracellular H2O2 to oxygen. Moreover, due to the in situ reduction process, the uniform Pt NPs distributed well on the surface of 3D-dendritic MSNs with high homogeneous dispersity. Additionally, a mitochondria-targeting ligand, triphenylphosphine (TPP), was conjugated to the Pt-decorated 3D-dendritic MSN composites to form a mitochondria targeted system for the PDT. In a combination of the peroxidase-like Pt NPs with mitochondria-targeting ability of TPP, a reactive oxygen species (ROS) burst in the mitochondria was achieved and resulted in the cell apoptosis. This well-designed system shows an enhanced PDT effect of killing A549 cells, and promotes a new H2O2-activatable strategy to overcome hypoxia for tumor PDT.

Development of Octyl Methoxy Cinnamates (OMC)/Silicon Dioxide (SiO₂) Nanoparticles by Sol-Gel Emulsion Method

Although octyl methoxy cinnamates (OMC) is the most used Ultraviolet B (UVB) filter in sunscreen, it has poor light stability in emulsion system. In this study, OMC/SiO₂ nanoparticles were prepared via sol-gel emulsion method. Tetraethoxy silane (TEOS) was used as the silica source to encapsulate OMC. Modification of experimental parameters such as stirring speed of condensation reaction and emulsion condition, pH value of acid-catalyzed, surfactant and different percentage of TEOS and OMC, adding of OMC and surfactant to different phase may affect the particle size, and yield and entrapment efficiency in preparation process of OMC/SiO₂ nanoparticles. Concluding all the parameter, we found that when condensation reaction and emulsion conditions are at 1000 rpm, pH 1.5, Span 80/Tween 20, TEOS/OMC ratios 1:1, OMC and surfactants added in oil phase, resulting in smaller particle sizes 476.5 nm, higher yield 95.8%, and higher entrapment efficiency 61.09%. Fourier transform infrared (FTIR) analysis demonstrated that OMC/SiO₂ nanoparticles were successfully prepared. In vitro release profile supposed that OMC/SiO₂ nanoparticles can delay OMC releasing and had 60.83% decreasing of cumulative amount. Therefore, the OMC/SiO₂ nanoparticles have the potential to develop as new sunscreen materials in the use for cosmetics field in the future.

Optical imaging and anticancer chemotherapy through carbon dot created hollow mesoporous silica nanoparticles

Multifunctional nanocarrier-based theranostics is currently considered to solve some key unmet challenges in cancer treatment. Here we report a nanocarrier platform, named carbon dot (CD) created mesoporous hollow organosilica (C-hMOS) nanoparticles, to deliver anticancer drug and to enable optical imaging. The hollow structure was formed by the removal of a nanorod core template, and at the same time, the fluorescent signal was endowed from the heat-treated organosilica network. Thanks to the hollow and mesoporous structure, the C-hMOS effectively loaded doxorubicin (DOX) for cancer chemotherapy. The DOX was released from C-hMOS highly sustainably (over 12days) and pH-dependently (pH 5.0 >pH 7.4). The DOX-loading C-hMOS internalized cancer cells efficiently (>90%), and induced cellular apoptosis including the expression of caspase-3. The treatment of C-hMOS to cancer cells enabled multi-color visualization in vitro, suggesting the possibility of cell tracing. Moreover, when injected intratumorally in mice, the C-hMOS exhibited strong optical signals in vivo along with a high optical stability (over a week). The injected C-hMOS were distributed only a fraction in liver but not in heart, lung, spleen or kidney and displayed good biocompatibility. The DOX-delivering C-hMOS significantly suppressed the in vivo tumor growth associated with apoptotic functions. Taken together, the developed C-hMOS nanoparticles can be a promising nanoplatform for drug delivery and in vivo imaging in cancer treatment.

STATEMENT OF SIGNIFICANCE

Multifunctional nanoparticles that combine chemotherapeutic ability with imaging modality comprise promising platform for cancer theranostics. Here we developed a novel theranostic nanoparticle, i.e., carbon-dot created mesoporous hollow silica nanoparticle, to offer unique merit for this purpose. The in vitro and in vivo findings to support this include: i) carbon dots with 1-2nm size in situ generated discretely and uniformly within silica network, ii) hollow and mesoporous structure effective for loading of DOX at high content, iii) release behavior of DOX in a sustainable and pH-dependent manner, iv) chemotherapeutic efficacy in killing cancer cells and suppressing tumor growth through DOX delivery, and v) carbon dot induced multi-color fluorescence imaging within cells and tumor tissues. These collective multifaceted properties may facilitate the novel carbon dot nanocarriers to be a potential candidate for delivering anticancer drug and non-invasive imaging in cancer treatment.

Sustained, Controlled and Stimuli-Responsive Drug Release Systems Based on Nanoporous Anodic Alumina with Layer-by-Layer Polyelectrolyte

Controlled drug delivery systems are an encouraging solution to some drug disadvantages such as reduced solubility, deprived biodistribution, tissue damage, fast breakdown of the drug, cytotoxicity, or side effects. Self-ordered nanoporous anodic alumina is an auspicious material for drug delivery due to its biocompatibility, stability, and controllable pore geometry. Its use in drug delivery applications has been explored in several fields, including therapeutic devices for bone and dental tissue engineering, coronary stent implants, and carriers for transplanted cells. In this work, we have created and analyzed a stimuli-responsive drug delivery system based on layer-by-layer pH-responsive polyelectrolyte and nanoporous anodic alumina. The results demonstrate that it is possible to control the drug release using a polyelectrolyte multilayer coating that will act as a gate.

Electrochemical immunosensor for detection of prostate specific antigen based on an acid cleavable linker into MSN-based controlled release system

A mesoporous silica nanoparticle (MSN)-based controlled release system with acid cleavable linkage was developed to fabricate an electrochemical immunosensor for the quantitative detection of the prostate-specific antigen (PSA). 3,9-Bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5.5]undecane functionalized mesoporous silica nanoparticles (MSN-Acetal) were used to immobilize the electron mediator thionine (Th). The encapsulation of Th molecules was achieved by capping the pores of MSN-Acetal with carboxylic acid modified Au nanoparticles (defined as MSN-Th-Au). Under the acidic conditions, the capped Au nanoparticles were removed from MSN-Th-Au through the hydrolysis of the acid-labile acetal linker, resulting in the release of encapsulated Th. In this work, the pH-responsive cargo release system was firstly used as the label of secondary anti-PSA for developing an electrochemical immunosensor, and amination Fe3O4 was used as the sensing matrix for immobilizing primary anti-PSA on magnetic carbon electrode surfaces. The specific recognition of PSA resulted in the attachment of MSN-Th-Au-secondary anti-PSA (MSN-Th-Au-Ab2) onto the electrode surfaces. Subsequently, the released Th was detected by differential pulse voltammetry under the acidic conditions. The developed cargo release system provided an innovative and reliable method for the detection of PSA because the response signal was correlated with the concentration of PSA. Under the optimal conditions, the electrochemical immunosensor exhibited a wide linear range of 0.001-5.0ng/mL with a low detection limit of 0.31pg/mL. Moreover, the developed immunosensor showed superior reproducibility and long-term stability, which has promising applications in bioassay and biosensing.

Facile synthesis of monodisperse of hollow mesoporous SiO2 nanoparticles and in-situ growth of Ag nanoparticles for antibacterial

Monodispersed hollow mesoporous silica nanoparticles (HMSNs) are successfully synthesized via a facile dual template method, in which poly(styrene-co-methyl methacrylate-co-methacrylic acid) (PS-PMMA-PMAA) particles are used as hard template for producing the hollow structure and cetyltrimethylammonium bromide (CTAB) used for introducing the mesopores in the silica shells. The obtained HMSNs possess uniform diameter and morphology, and the shell of which could be adjusted by changing the addition of silicon precursor. The synthesized HMSNs have been characterized by transmission electron microscopy (TEM) and nitrogen physisorption. Furthermore, the HMSNs are used as support for in-situ deposition of silver nanoparticles (Ag NPs) using n-butylamine as reducing agent for AgNO3 in ethanol. Significantly, Ag NPs were successfully supported in the HMSNs without any aggregation. The Ag-deposited HMSNs showed excellent dispersibility in ethanol and water, and their antibacterial activity against Escherichia coli (E. coli) ATCC 25922 and Staphylococcus aureus (S. aureus) ATCC 6538 have been demonstrated. Therefore, the unique nanostructure based on the HMSNs provided a useful platform for the fabrication of antibacterial agent with superior activity and accessibility. And also, it is expected to be a significant template for the synthesis of other novel nanostructures.

Formation of mesoporous silica nanoparticles with tunable pore structure as promising nanoreactor and drug delivery vehicle

Mesoporous silica nanoparticles with tunable pore structures have been successfully fabricated by simply tuning the ethanol amounts in the precursor.

Magnetic conducting polymer/mesoporous SiO2 yolk/shell nanomaterials: multifunctional nanocarriers for controlled release of doxorubicin

Fe₃O₄/polyaniline@mesoporous SiO₂ yolk@shell nanostructures as multifunctional nanocarriers for controlled release of doxorubicin have been demonstrated.

Intermediate pickering emulsion formation as a means for synthesizing hollow mesoporous silica nanoparticles

Particle and surfactant-stabilized emulsion droplets formed in situ serve as templates for hollow silica nanoparticle growth.

A soft–hard template approach towards hollow mesoporous silica nanoparticles with rough surfaces for controlled drug delivery and protein adsorption

Novel hollow mesoporous silica nanoparticles (HMSNs) with rough surfaces have been successfully prepared using a facile soft–hard template route.

Redox-sensitive mesoporous silica nanoparticles functionalized with PEG through a disulfide bond linker for potential anticancer drug delivery

In this paper, redox-sensitive mesoporous silica nanoparticles (MSNs–SS–PEG) were successfully synthesized using silica nanoparticles modified with a thiol group (MSNs–SH) and thiol-functionalized methoxy polyethylene glycol (MeOPEG–SH).