Degradability and Clearance of Silicon, Organosilica, Silsesquioxane, Silica Mixed Oxide, and Mesoporous Silica Nanoparticles

Modular Metal-Organic Polyhedra Superassembly: From Molecular-Level Design to Targeted Drug Delivery

Targeted drug delivery remains at the forefront of biomedical research but remains a challenge to date. Herein, the first superassembly of nanosized metal-organic polyhedra (MOP) and their biomimetic coatings of lipid bilayers are described to synergistically combine the advantages of micelles and supramolecular coordination cages for targeted drug delivery. The superassembly technique affords unique hydrophobic features that endow individual MOP to act as nanobuilding blocks and enable their superassembly into larger and well-defined nanocarriers with homogeneous sizes over a broad range of diameters. Various cargos are controllably loaded into the MOP with high payloads, and the nanocages are then superassembled to form multidrug delivery systems. Additionally, functional nanoparticles are introduced into the superassemblies via a one-pot process for versatile bioapplications. The MOP superassemblies are surface-engineered with epidermal growth factor receptors and can be targeted to cancer cells. In vivo studies indicated the assemblies to have a substantial circulation half-life of 5.6 h and to undergo renal clearance-characteristics needed for nanomedicines.

Degradability and Clearance of Inorganic Nanoparticles for Biomedical Applications

Inorganic nanoparticles with tunable and diverse properties hold tremendous potential in the field of nanomedicine, while having non-negligible toxicity concerns in healthy tissues/organs that have resulted in their restricted clinical translation to date. In the past decade, the emergence of biodegradable or clearable inorganic nanoparticles has made it possible to completely solve this long-standing conundrum. A comprehensive understanding of the design of these inorganic nanoparticles with their metabolic performance in the body is of crucial importance to advance clinical trials and expand their biological applications in disease diagnosis. Here, a diverse variety of biodegradable or clearable inorganic nanoparticles regarding considerations of the size, morphology, surface chemistry, and doping strategy are highlighted. Their pharmacokinetics, pathways of metabolism in the body, and time required for excretion are discussed. Some inorganic materials intrinsically responsive to various conditions in the tumor microenvironment are also introduced. Finally, an overview of the encountered challenges is provided along with an outlook for applying these inorganic nanoparticles toward future clinical translations.

Functional Mesoporous Silica Nanocomposites: Biomedical applications and Biosafety

The rise and development of nanotechnology has enabled the creation of a wide number of systems with new and advantageous features to treat cancer. However, in many cases, the lone application of these new nanotherapeutics has proven not to be enough to achieve acceptable therapeutic efficacies. Hence, to avoid these limitations, the scientific community has embarked on the development of single formulations capable of combining functionalities. Among all possible components, silica-either solid or mesoporous-has become of importance as connecting and coating material for these new-generation therapeutic nanodevices. In the present review, the most recent examples of fully inorganic silica-based functional composites are visited, paying particular attention to those with potential biomedical applicability. Additionally, some highlights will be given with respect to their possible biosafety issues based on their chemical composition.

Spatially Controlled Surface Modification of Porous Silicon for Sustained Drug Delivery Applications

A new and facile approach to selectively functionalize the internal and external surfaces of porous silicon (pSi) for drug delivery applications is reported. To provide a surface that is suitable for sustained drug release of the hydrophobic cancer chemotherapy drug camptothecin (CPT), the internal surfaces of pSi films were first modified with 1-dodecene. To further modify the external surface of the pSi samples, an interlayer was applied by silanization with (3-aminopropyl)triethoxysilane (APTES) following air plasma treatment. In addition, copolymers of N-(2-hydroxypropyl) acrylamide (HPAm) and N-benzophenone acrylamide (BPAm) were grafted onto the external pSi surfaces by spin-coating and UV crosslinking. Each modification step was verified using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, water contact angle (WCA) measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). In order to confirm that the air plasma treatment and silanization step only occurred on the top surface of pSi samples, confocal microscopy was employed after fluorescein isothiocyanate (FITC) conjugation. Drug release studies carried out over 17 h in PBS demonstrated that the modified pSi reservoirs released CPT continuously, while showing excellent stability. Furthermore, protein adsorption and cell attachment studies demonstrated the ability of the graft polymer layer to reduce both significantly. In combination with the biocompatible pSi substrate material, the facile modification strategy described in this study provides access to new multifunctional drug delivery systems (DDS) for applications in cancer therapy.

Nanoparticle mediated silencing of tenascin C in hepatic stellate cells: effect on inflammatory gene expression and cell migration

Mesoporous silica nanoparticles efficiently knock-down tenascin-C in hepatic stellate cells resulting in decrease of inflammatory cytokine levels and hepatocyte migration.

Exploring the cell-protein-mineral interfaces: Interplay of silica (nano)rods@collagen biocomposites with human dermal fibroblasts

The benefits of associating biological polymers with nanomaterials within functional bionanocomposite hydrogels have already been evidenced both in vitro and in vivo. However their development as effective biomaterials requires to understand and tune the interactions at the cell-protein-mineral ternary interface. With this purpose, we have studied here the impact of silica (nano)rods on the structural and rheological properties of type I collagen hydrogels ​and on the behavior of human dermal fibroblasts. High collagen concentrations were beneficial to the material mechanical properties, whereas silica rods could exert a positive effect on these at both low and high content. Electron microscopy evidenced strong bio-mineral interactions, emphasizing the true composite nature of these materials. In contrast, adhesion and proliferation studies showed that, despite these interactions, fibroblasts can discriminate between the protein and the inorganic phases and penetrate the collagen network to limit direct contact with silica. Such a divergence between physicochemical characteristics and biological responses has major implications for the prediction of the in vivo fate of nanocomposite biomaterials.

Cellular Internalization-Induced Aggregation of Porous Silicon Nanoparticles for Ultrasound Imaging and Protein-Mediated Protection of Stem Cells

Nanotechnology employs multifunctional engineered materials in the nanoscale range that provides many opportunities for translational stem cell research and therapy. Here, a cell-penetrating peptide (virus-1 transactivator of transcription)-conjugated, porous silicon nanoparticle (TPSi NP) loaded with the Wnt3a protein to increase both the cell survival rate and the delivery precision of stem cell transplantation via a combinational theranostic strategy is presented. The TPSi NP with a pore size of 10.7 nm and inorganic framework enables high-efficiency loading of Wnt3a, prolongs Wnt3a release, and increases antioxidative stress activity in the labeled mesenchymal stem cells (MSCs), which are highly beneficial properties for cell protection in stem cell therapy for myocardial infarction. It is confirmed that the intracellular aggregation of TPSi NPs can highly amplify the acoustic scattering of the labeled MSCs, resulting in a 2.3-fold increase in the ultrasound (US) signal compared with that of unlabeled MSCs. The translational potential of the designed nanoagent for real-time US imaging-guided stem cell transplantation is confirmed via intramyocardial injection of labeled MSCs in a nude mouse model. It is proposed that the intracellular aggregation of protein drug-loaded TPSi NPs could be a simple but robust strategy for improving the therapeutic effect of stem cell therapy.

Recent development in biodegradable nanovehicle delivery system-assisted immunotherapy

A schematic illustration of BNDS biodegradation and release antigen delivery for assisting immunotherapy.

Inhibition of metal-induced amyloid β-peptide aggregation by a blood–brain barrier permeable silica–cyclen nanochelator

Alzheimer's disease (AD) is a neurodegenerative malady associated with amyloid β-peptide (Aβ) aggregation in the brain. Metal ions play important roles in Aβ aggregation and neurotoxicity. Metal chelators are potential therapeutic agents for AD because they could sequester metal ions from the Aβ aggregates and reverse the aggregation. The blood–brain barrier (BBB) is a major obstacle for drug delivery to AD patients. Herein, a nanoscale silica–cyclen composite combining cyclen as the metal chelator and silica nanoparticles as a carrier was reported. Silica–cyclen was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and dynamic light scattering (DLS). The inhibitory effect of the silica–cyclen nanochelator on Zn²⁺- or Cu²⁺-induced Aβ aggregation was investigated by using a BCA protein assay and TEM. Similar to cyclen, silica–cyclen can effectively inhibit the Aβ aggregation and reduce the generation of reactive oxygen species induced by the Cu–Aβ₄₀ complex, thereby lessening the metal-induced Aβ toxicity against PC12 cells. In vivo studies indicate that the silica–cyclen nanochelator can cross the BBB, which may provide inspiration for the construction of novel Aβ inhibitors.

A BBB-passable nanoscale silica–cyclen chelator effectively reduces the metal-induced Aβ aggregates and related ROS, thereby decreasing the neurotoxicity of Aβ.

A Toolbox for the Synthesis of Multifunctionalized Mesoporous Silica Nanoparticles for Biomedical Applications

Mesoporous silica nanoparticles (MSNs) are considered as promising next-generation nanocarriers for health-related applications. However, their effectiveness mostly relies on their efficient and surface-specific functionalization. In this contribution, we explored different strategies for the rational multistep synthesis of functional MCM-48-type MSNs with selectively created active inner and/or external surfaces. Functional groups were first installed using a combination of (delayed) co-condensation and post-grafting procedures. Both amine [(3-aminopropyl)triethoxysilane (APTS)] and thiol [(3-mercaptopropyl)trimethoxysilane (MPTS)] silanes were used, in various addition sequences. Following this, the different platforms were further functionalized with polyethylene glycol and/or with a pro-chelate ligand used as a magnetic resonance imaging contrast agent (diethylenetriaminepentaacetic acid chelates) and/or loaded with quercetin and/or grafted with an organic dye (rhodamine). The efficiency of the multiple grafting strategies and the effects on the MSN carrier properties are presented. Finally, the colloidal stability of the different systems was evaluated in physiological media, and preliminary tests were performed to verify their drug release capability. The use of MPTS appeared beneficial when compared to APTS in delayed co-condensation procedures to preserve both selective distribution of the functional groups, reactive functionality, and pore ordering. Our results provide in-depth insights into the efficient design of (multi)functional MSNs and especially on the crucial role played by the sequence of step-by-step functionalization methods aiming to produce multipurpose and stable bioplatforms.

Acidity/Reducibility Dual-Responsive Hollow Mesoporous Organosilica Nanoplatforms for Tumor-Specific Self-Assembly and Synergistic Therapy

Featured with a large surface area, uniform interpenetrating mesopores, diverse organic framework hybridization, and well-defined surface properties, the hollow mesoporous organosilica nanoparticle (HMON) represents a promising paradigm in drug delivery systems with excellent biocompatibility. However, effective tumor accumulation and precise cancer theranostics of the HMON still remain a challenge. In this study, an "ammonia-assisted hot water etching" method is applied for the successful construction of sub-50 nm thioether/phenylene dual-hybridized HMON with low hemolytic effect. Particularly, the surface modification with Mo(VI)-based polyoxometalate (POM) clusters drives the self-assembly of HMON in the mild acidic tumor microenvironment (TME) to achieve enhanced tumor retention and accumulation. More importantly, the reducibility-activated Mo(VI)-to-Mo(V) conversion within POM not only endows the POM-anchored HMON with outstanding TME-responsive photoacoustic (PA) imaging contrast and photothermal therapy (PTT) performance but also plays an indispensable role in controllably triggering the decomposition of the Mn2(CO)10 payload for CO release, which gives rise to remarkable synergistic PTT-enhanced CO gas therapy for complete tumor eradication. By harnessing the unique acidic and redox properties of TME, the judiciously designed smart POM-anchored HMON nanoplatform is expected to act as a "magic bomb" to selectively destroy cancer without damaging normal tissues. This nanoplatform holds significant potential in realizing TME-responsive self-assembly for enhanced tumor accumulation and precise tumor-specific synergistic therapy, which is very promising for clinical translation.

Bone remodeling-inspired dual delivery electrospun nanofibers for promoting bone regeneration

Developing a highly bioactive bone tissue engineering scaffold that can modulate the bone remodeling process for promoting bone regeneration is a great challenge. In order to tackle this issue, inspired by the balance between bone resorption and formation in the bone remodeling process, here we developed a mesoporous silicate nanoparticle (MSN)-based electrospun polycaprolactone (PCL)/gelatin nanofibrous scaffold to achieve dual delivery of alendronate (ALN) and silicate for a synergetic effect in modulating bone remodeling, where ALN inhibited the bone-resorbing process via preventing guanosine triphosphate-related protein expression, and silicate promoted the bone-forming process via improving vascularization and bone calcification. The scaffold was successfully prepared by encapsulation of ALN into MSNs (ALN@MSNs) and co-electrospinning of an acetic acid-mediated PCL/gelatin homogeneous solution with well-dispersed ALN@MSNs. The results of ALN and Si element release profiles indicated that the ALN@MSN-loaded nanofibers achieved dual release of ALN and silicate (produced due to the hydrolysis of MSNs) simultaneously. The bone repair data from a rat critical-sized cranial defect model revealed that the developed strategy accelerated the healing time from 12 weeks to 4 weeks, almost three times faster, while the other nanofiber groups only had limited bone regeneration at 4 weeks. In addition, we used interactive double-factor analysis of variance for the data of bone volume and maturity to evaluate the synergetic effect of ALN and silicate in promoting bone regeneration, and the result clearly proved our original design and hypothesis. In summary, the presented bone remodeling-inspired electrospun nanofibers with dual delivery of ALN and silicate may be highly promising for bone repair in the clinic.

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.

Chemodrug-Gated Biodegradable Hollow Mesoporous Organosilica Nanotheranostics for Multimodal Imaging-Guided Low-Temperature Photothermal Therapy/Chemotherapy of Cancer

Noninvasive physical treatment with relatively low intensity stimulation and the development of highly efficient anticancer medical strategy are still desirable for cancer therapy. Herein a versatile, biodegradable, hollow mesoporous organosilica nanocapsule (HMONs) nanoplatform that is capped by the gemcitabine (Gem) molecule through a pH-sensitive acetal covalent bond is designed. The fabricated nanocapsule exhibits desirable small molecule release at the tumor tissues/cell sites and shows a reduced risk for drug accumulation. After loading indocyanine green (ICG), the heat-shock protein 90 (Hsp 90) inhibitor, and 17AAG and modification with polyethylene glycol (NH₂-PEG), the resulting ICG-17AAG@HMONs-Gem-PEG exhibited a precisely controlled release of ICG and 17AAG and low-temperature photothermal therapy (PTT) (∼41 °C) with excellent tumor destruction efficacy. In addition, ICG loading conferred the nanoplatform with near-infrared fluorescence imaging (FL) and photoaccoustic (PA) imaging capability. In short, this work not only presents a smart drug self-controlled nanoplatform with pH-responsive payload release and theranostic performance but also provides an outstanding low-temperature PTT strategy, which is highly valid in the inhibition of cancer cells with minimal damage to the organism. Therefore, this research provides a paradigm that has a chemodrug-gated HMONs-based theranostic nanoplatform with intrinsic biodegradability, multimodal imaging capacity, high low-temperature PTT/chemotherapy efficacy, and reduced systemic toxicity.

Magnetic nanoarchitectures for cancer sensing, imaging and therapy

The use of magnetic nanoparticles for sensing and theranostics of cancer has grown substantially in the last decade. Since the pioneering studies, which reported magnetic nanoparticles for bio-applications more than fifteen years ago, nanomaterials have increased in complexity with different shapes (nanoflowers, nanospheres, nanocubes, nanostars etc.) and compositions (e.g. core-shell) of nanoparticles for an increase in the sensitivity (imaging or sensing) and efficiency through synergistic treatments such as hyperthermia and drug delivery. In this review, we describe recent examples concerning the use of magnetic nanoparticles for bio-applications, from the surface functionalization methods to the development of cancer sensors and nanosystems for magnetic resonance and other imaging methodologies. Multifunctional nanosystems (nanocomposites, core shell nanomaterials) for theranostic applications involving treatments such as hyperthermia, photodynamic therapy, targeted drug delivery, and gene silencing are also described. These nanomaterials could be the future of medicine, although their complexity raises concerns about their safety.

Dealing with Skin and Blood-Brain Barriers: The Unconventional Challenges of Mesoporous Silica Nanoparticles

Advances in nanotechnology for drug delivery are fostering significant progress in medicine and diagnostics. The multidisciplinary nature of the nanotechnology field encouraged the development of innovative strategies and materials to treat a wide range of diseases in a highly specific way, which allows reducing the drug dosage and, consequently, improving the patient's compliance. Due to their good biocompatibility, easy synthesis, and high versatility, inorganic frameworks represent a valid tool to achieve this aim. In this context, Mesoporous Silica Nanoparticles (MSNs) are emerging in the biomedical field. For their ordered porosity and high functionalizable surface, achievable with an inexpensive synthesis process and being non-hazardous to biological tissues, MSNs offer ideal solutions to host, protect, and transport drugs to specific target sites. Extensive literature exists on the use of MSNs as targeted vehicles for systemic (chemo) therapy and for imaging/diagnostic purposes. However, the aim of this review is to give an overview of the last updates on the potential applications of the MSNs for Topical Drug Delivery (TDD) and as drug delivery systems into the brain, discussing their performances and advantages in dealing with these intriguing biological barriers.

Large-Pore Mesoporous-Silica-Coated Upconversion Nanoparticles as Multifunctional Immunoadjuvants with Ultrahigh Photosensitizer and Antigen Loading Efficiency for Improved Cancer Photodynamic Immunotherapy

Reported immunoadjuvants still have many limitations, such as inferior cellular uptake capacity and biocompatibility, overly large particle sizes, single function, and unsatisfactory therapeutic efficacy. Here, large-pore mesoporous-silica-coated upconversion nanoparticles (UCMSs) with a size of less than 100 nm are successfully prepared by a typical silica sol-gel reaction using mesitylene as a pore-swelling agent and are applied as a novel immunoadjuvant. The obtained UCMSs not only show significantly higher loadings for the photosensitizers merocyanine 540 (MC540), model proteins (chicken ovalbumin (OVA)), and tumor antigens (tumor cell fragment (TF)), but also are successfully employed for highly efficient in vivo vaccine delivery. The prepared UCMSs-MC540-OVA under 980 nm near-infrared irradiation shows the best synergistic immunopotentiation action, verified by the strongest Th1 and Th2 immune responses and the highest frequency of CD4⁺ , CD8⁺ , and effector-memory T cells. Additionally, nanovaccines UCMSs-MC540-TF can more effectively inhibit tumor growth and increase the survival of colon cancer (CT26)-tumor-bearing BALB/c mice compared with either photodynamic therapy or immunological therapy alone, suggesting the enhanced immunotherapy efficacy and clinical potential of UCMSs as immunoadjuvants for cancer immunotherapy.

Enhancing oral bioavailability of poorly soluble drugs with mesoporous silica based systems: opportunities and challenges

Porous silica-based drug delivery systems have shown considerable promise for improving the oral delivery of poorly water-soluble drugs. More specifically, micro- and meso-porous silica carriers have high surface areas with associated ability to physically adsorb high-drug loads in a molecular or amorphous form; this allows molecular state drug release in aqueous gastrointestinal environments, potential for supersaturation, and hence facilitates enhanced absorption and increased bioavailability. This review focuses primarily on the ability of porous silica materials to modulate in vitro drug release and enhance in vivo biopharmaceutical performance. The key considerations identified and addressed are the physicochemical properties of the porous silica materials (e.g. the particle and pore size, shape, and surface chemistry), drug specific properties (e.g. pKa, solubility, and nature of interactions with the silica carrier), potential for both immediate and controlled release, drug release mechanisms, potential for surface functionalization and inclusion of precipitation inhibitors, and importance of utilizing relevant and effective in vitro dissolution methods with discriminating dissolution media that provides guidance for in vivo outcomes (i.e. IVIVC).

Redox/pH dual-controlled release of chlorhexidine and silver ions from biodegradable mesoporous silica nanoparticles against oral biofilms

BACKGROUND

Oral plaque biofilms pose a threat to periodontal health and are challenging to eradicate. There is a growing belief that a combination of silver nanoparticles and chlorhexidine (CHX) is a promising strategy against oral biofilms.

PURPOSE

To overcome the side effects of this strategy and to exert maximum efficiency, we fabricated biodegradable disulfide-bridged mesoporous silica nanoparticles (MSNs) to co-deliver silver nanoparticles and CHX for biofilm inhibition.

MATERIALS AND METHODS

CHX-loaded, silver-decorated mesoporous silica nanoparticles (Ag-MSNs@CHX) were fabricated after CHX loading, and the pH- and glutathione-responsive release profiles of CHX and silver ions along with their mechanism of degradation were systematically investigated. Then, the efficacy of Ag-MSNs@CHX against Streptococcus mutans and its biofilm was comprehensively assessed by determining the minimum inhibitory concentration, minimum bactericidal concentration, minimal biofilm inhibitory concentration, and the inhibitory effect on S. mutans biofilm formation. In addition, the biosafety of nanocarriers was evaluated by oral epithelial cells and a mouse model.

RESULTS

The obtained Ag-MSNs@CHX possessed redox/pH-responsive release properties of CHX and silver ions, which may be attributed to the redox-triggered matrix degradation mechanism of exposure to biofilm-mimetic microenvironments. Ag-MSNs@CHX displayed dose-dependent antibacterial activity against planktonic and clone formation of S. mutans. Importantly, Ag-MSNs@CHX had an increased and long-term ability to restrict the growth of S. mutans biofilms compared to free CHX. Moreover, Ag-MSNs@CHX showed less cytotoxicity to oral epithelial cells, whereas orally administered Ag-MSNs exhibited no obvious toxic effects in mice.

CONCLUSION

Our findings constitute a highly effective and safe strategy against biofilms that has a good potential as an oral biofilm therapy.

Radiation-responsive scintillating nanotheranostics for reduced hypoxic radioresistance under ROS/NO-mediated tumor microenvironment regulation

Abstract: Hypoxia-induced radioresistance is the primary reason for failure of tumor radiotherapy (RT). Changes within the irradiated tumor microenvironment (TME) including oxygen, reactive oxygen species (ROS) and nitric oxide (NO) are closely related to radioresistance. Therefore, there is an urgent need to develop new approaches for overcoming hypoxic radioresistance by incorporating TME regulation into current radiotherapeutic strategies.

Methods: Herein, we explored a radiation-responsive nanotheranostic system to enhance RT effects on hypoxic tumors by multi-way therapeutic effects. This system was developed by loading S-nitrosothiol groups (SNO, a NO donor) and indocyanine green (ICG, a photosensitizer) onto mesoporous silica shells of Eu³⁺-doped NaGdF₄ scintillating nanocrystals (NSC).

Results: Under X-ray radiation, this system can increase the local dosage by high-Z elements, promote ROS generation by X-ray-induced photodynamic therapy, and produce high levels of NO to enhance tumor-killing effects and improve hypoxia via NO-induced vasodilation. In vitro and in vivo studies revealed that this combined strategy can greatly reinforce DNA damage and apoptosis of hypoxic tumor cells, while significantly suppressing tumor growth, improving tumor hypoxia and promoting p53 up-regulation and HIF1α down-regulation. In addition, this system showed pronounced tumor contrast performance in T₁-weighted magnetic resonance imaging and computed tomography.

Conclusion: This work demonstrates the great potential of scintillating nanotheranostics for multimodal imaging-guided X-ray radiation-triggered tumor combined therapy to overcome radioresistance.

Aerosol-synthesized siliceous nanoparticles: impact of morphology and functionalization on biodistribution

Introduction

Siliceous nanoparticles (NPs) have been extensively studied in nanomedicine due to their high biocompatibility and immense biomedical potential. Although numerous technologies have been developed, the synthesis of siliceous NPs for biomedical applications mainly relies on a few core technologies predominantly intended to produce spherical-shaped NPs.

Methods

In this context, the impact of different morphologies of siliceous NPs on biodistribution in vivo is limited. In the present study, we developed a novel technique based on an aerosol silane reactor to produce sintered silicon NPs of similar size but different surface areas due to distinct spherical subunits. Silica-converted particles were functionalized for radiolabeling with copper-64 (⁶⁴Cu) to systematically analyze their behavior in the passive targeting of A431 tumor xenografts in mice after intravenous injection.

Results

While low nonspecific uptake was observed in most organs, the majority of particles were accumulated in the liver, spleen, and lung. Depending on the morphologies and function-alization, significant differences in the uptake profiles of the particles were observed. In terms of tumor uptake, spherical shapes with lower surface areas showed the highest accumulation and tumor-to-blood ratios of all investigated particles.

Conclusion

This study highlights the importance of shape and fuctionalization of siliceous NPs on organ and tumor accumulation as significant factors for biomedical applications.

Silica-Based Nanoparticles for Protein Encapsulation and Delivery

Although conceptually obvious, the effective delivery of proteins in therapeutic applications is far from being a routine practice. The major limitation is the conservation of protein physicochemical identity during the transport to the target site. In this regard, nanoparticle-based systems offer new intriguing possibilities, provided that (i) the harsh and denaturating conditions typically used for nanoparticle synthesis are avoided or mitigated; and (ii) nanoparticle biocompatibility and degradation (for protein release) are optimized. Here, we tackle these issues by starting from a nanoparticle architecture already tested for small chemical compounds. In particular, silica-shielded liposomes are produced and loaded with a test protein (i.e., Green Fluorescent Protein) in an aqueous environment. We demonstrate promising results concerning protein encapsulation, protection during intracellular trafficking and final release triggered by nanoparticle degradations in acidic organelles. We believe this proof of principle may open new applications and developments for targeted and efficient protein delivery.

A swarm of slippery micropropellers penetrates the vitreous body of the eye

The intravitreal delivery of therapeutic agents promises major benefits in the field of ocular medicine. Traditional delivery methods rely on the random, passive diffusion of molecules, which do not allow for the rapid delivery of a concentrated cargo to a defined region at the posterior pole of the eye. The use of particles promises targeted delivery but faces the challenge that most tissues including the vitreous have a tight macromolecular matrix that acts as a barrier and prevents its penetration. Here, we demonstrate novel intravitreal delivery microvehicles-slippery micropropellers-that can be actively propelled through the vitreous humor to reach the retina. The propulsion is achieved by helical magnetic micropropellers that have a liquid layer coating to minimize adhesion to the surrounding biopolymeric network. The submicrometer diameter of the propellers enables the penetration of the biopolymeric network and the propulsion through the porcine vitreous body of the eye over centimeter distances. Clinical optical coherence tomography is used to monitor the movement of the propellers and confirm their arrival on the retina near the optic disc. Overcoming the adhesion forces and actively navigating a swarm of micropropellers in the dense vitreous humor promise practical applications in ophthalmology.

Establishing the effects of mesoporous silica nanoparticle properties on in vivo disposition using imaging-based pharmacokinetics

The progress of nanoparticle (NP)-based drug delivery has been hindered by an inability to establish structure-activity relationships in vivo. Here, using stable, monosized, radiolabeled, mesoporous silica nanoparticles (MSNs), we apply an integrated SPECT/CT imaging and mathematical modeling approach to understand the combined effects of MSN size, surface chemistry and routes of administration on biodistribution and clearance kinetics in healthy rats. We show that increased particle size from ~32- to ~142-nm results in a monotonic decrease in systemic bioavailability, irrespective of route of administration, with corresponding accumulation in liver and spleen. Cationic MSNs with surface exposed amines (PEI) have reduced circulation, compared to MSNs of identical size and charge but with shielded amines (QA), due to rapid sequestration into liver and spleen. However, QA show greater total excretion than PEI and their size-matched neutral counterparts (TMS). Overall, we provide important predictive functional correlations to support the rational design of nanomedicines.

Nanoparticle applications are limited by insufficient understanding of physiochemical properties on in vivo disposition. Here, the authors explore the influence of size, surface chemistry and administration on the biodisposition of mesoporous silica nanoparticles using image-based pharmacokinetics.

Mesoporous Silica Nanoparticles for Dual-Mode Chemo-Sonodynamic Therapy by Low-Energy Ultrasound

Low-energy ultrasound (LEUS), exhibiting obvious advantages as a safe therapeutic strategy, would be promising for cancer therapy. We had synthesized a LEUS-responsive targeted drug delivery system based on functional mesoporous silica nanoparticle for cancer therapy. Paclitaxel (PTX) was loaded in mesoporous silica nanoparticles with a hydrophobic internal channel, and folic acid (FA) functionalized β-Cyclodextrin (β-CD) was capped on the surface of the nanoparticles (DESN), which acted as a cancer-targeting moiety and solubilizer. The existence of a hydrophobic internal channel in the DESN was beneficial to the storage of hydrophobic PTX, along with the enhancement of the cavitation effect produced by mild low-energy ultrasound (LEUS, ≤1.0 W/cm², 1 MHz). The DESN showed significantly enhanced cavitation effect, selective targeting, and achieved a rapid drug release under mild LEUS. To investigate the in vivo antitumor efficacy of the DESN upon LEUS irradiation, we established a 4T1 mammary tumor model. The DESN were confirmed to be of great biodegradability/biocompatibility. The tumor growth was significantly inhibited when the mice were treated with DESN (10 mg/kg) + LEUS with the relative tumor volume reduced to 4.72 ± 0.70 compared with the control group (V/V₀ = 17.12 ± 2.75). The DESN with LEUS represented excellent inhibiting effect on tumor cell in vivo. This work demonstrated that DESN mediating dual mode chemo-sonodynamic therapy could be triggered by extracorporeal remote control, may suggest a promising clinical application in cancer therapy.

Exogenous/Endogenous-Triggered Mesoporous Silica Cancer Nanomedicine

Recent advances in nanomedicine-based theranostic platforms have catalyzed the generation of new theranostic modalities for pathological abnormalities, such as cancer. Mesoporous silica-based nanomedicines, which feature unique physicochemical properties and specific applicability, are extensively explored for numerous oncological applications. Due to the well-defined morphology, specific surface area, and pore volume, mesoporous silica nanoparticle (MSN)-based theranostic platforms have provided unprecedented opportunities for the development of next-generation cancer nanomedicine. However, current understanding on the underlying mechanisms of how these feasible theranostic platforms interact with exogenous/endogenous triggers and how this unique responsiveness for optimized cancer therapy can be taken advantage of is still preliminary. In this progress report, efforts are made to give a comprehensive overview of the development of MSN-based "smart" theranostic platforms, from exogenous physical irradiation-triggered platforms for localized therapy to endogenous biological stimulus-triggered platforms for tumor microenvironment responsiveness. It is highly expected that these elaborately fabricated MSN-based nanoformulations will play an indispensable role in the efficient cancer therapy based on their high therapeutic outcome and reduced side effects.

Porous Inorganic Carriers Based on Silica, Calcium Carbonate and Calcium Phosphate for Controlled/Modulated Drug Delivery: Fresh Outlook and Future Perspectives

Porous inorganic nanostructured materials are widely used nowadays as drug delivery carriers due to their adventurous features: suitable architecture, large surface area and stability in the biological fluids. Among the different types of inorganic porous materials, silica, calcium carbonate, and calcium phosphate have received significant attention in the last decade. The use of porous inorganic materials as drug carriers for cancer therapy, gene delivery etc. has the potential to improve the life expectancy of the patients affected by the disease. The main goal of this review is to provide general information on the current state of the art of synthesis of the inorganic porous particles based on silica, calcium carbonate and calcium phosphate. Special focus is dedicated to the loading capacity, controllable release of drugs under internal biological stimuli (e.g., pH, redox, enzymes) and external noninvasive stimuli (e.g., light, magnetic field, and ultrasound). Moreover, the diverse compounds to deliver with silica, calcium carbonate and calcium phosphate particles, ranging from the commercial drugs to genetic materials are also discussed.

Gel-Mediated Electrospray Assembly of Silica Supraparticles for Sustained Drug Delivery

Supraparticles (SPs) composed of smaller colloidal particles provide a platform for the long-term, controlled release of therapeutics in biomedical applications. However, current synthesis methods used to achieve high drug loading and those involving biocompatible materials are often tedious and low throughput, thereby limiting the translation of SPs to diverse applications. Herein, we present a simple, effective, and automatable alginate-mediated electrospray technique for the assembly of robust spherical silica SPs (Si-SPs) for long-term (>4 months) drug delivery. The Si-SPs are composed of either porous or nonporous primary Si particles within a decomposable alginate matrix. The size and shape of the Si-SPs can be tailored by controlling the concentrations of alginate and silica primary particles used and key electrospraying parameters, such as flow rate, voltage, and collector distance. Furthermore, the performance (including drug loading kinetics, loading capacity, loading efficiency, and drug release) of the Si-SPs can be tuned by changing the porosity of the primary particles and through the retention or removal (via calcination) of the alginate matrix. The structure and morphology of the Si-SPs were characterized by electron microscopy, dynamic light scattering, N₂ adsorption-desorption analysis, and X-ray photoelectron spectroscopy. The cytotoxicity and degradability of the Si-SPs were also examined. Drug loading kinetics and loading capacity for six different types of Si-SPs, using a model protein drug (fluorescently labeled lysozyme), demonstrate that Si-SPs prepared from primary silica particles with large pores can load significant amounts of lysozyme (∼10 μg per SP) and exhibit sustained, long-term release of more than 150 days. Our experiments show that Si-SPs can be produced through a gel-mediated electrospray technique that is robust and automatable (important for clinical translation and commercialization) and that they present a promising platform for long-term drug delivery.

Mesoporous Silica-Based Nanoparticles for Light-Actuated Biomedical Applications via Near-Infrared Two-Photon Absorption

In this review, we highlight the design of nanomaterials for two-photon excitation, in order to treat tumors with a high accuracy. Indeed two-photon excitation allows remote control of the nanoparticles with a spatio-temporal resolution. The nanomaterials are based on mesoporous silica-organosilica nanoparticles including core-shell systems. The therapeutic treatments include drug delivery, photodynamic therapy, gene silencing, and their combinations. At first, the nanosystems designed for two-photon-triggered cytotoxic drug delivery are reviewed. Then the nanomaterials prepared for two-photon photodynamic therapy and reactive oxygen species delivery are discussed. Finally, the nanosystems combining drug delivery or gene silencing with two-photon photodynamic therapy are presented. Due to the rapid progresses concerning two-photon-excited nanomaterials and the interest of near-infrared light to treat deep tumors, we believe this technology could be of high interest for the personalized medicine of the future.

Biodistribution and Excretion of Intravenously Injected Mesoporous Silica Nanoparticles: Implications for Drug Delivery Efficiency and Safety

Mesoporous silica nanoparticles (MSNs) are currently attracting a high interest for use as drug carriers in vivo. To date only data on the biodistribution in small animals are available. As any nanoparticle system, the MSNs typically accumulate in the RES organs lung, liver, and spleen upon intravenous (i.v.) administration. However, the literature data are partly inconclusive, which can be connected to the wide variability of the experimental designs, differing for example in particle size and shape, mesopore size, and surface functionalization, as well as the animal models used, the amount administered, and the means for particle detection. The present review is an attempt to summarize the literature to date with main focus on the increasing number of studies related to quantitative full body distributions. Whenever possible, attempts are also made to discuss differences in experimental observations between studies. Finally, an outlook is given listing some open issues, and highlighting the need for more standardized experimental designs in order to allow for a faster identification of optimal particle characteristics for drug delivery applications of MSNs.

Biodegradable Silica-Based Nanoparticles: Dissolution Kinetics and Selective Bond Cleavage

Silica-based nanomaterials are extensively used in industrial applications and academic biomedical research, thus properly assessing their toxicity and biodegradability is essential for their safe and effective formulation and use. Unfortunately, there is often a lot of confusion in the literature with respect to the toxicity and biodegradability of silica since various studies have yielded contradictory results. In this contribution, we first endeavor to underscore that the simplistic model of silica should be discarded in favor of a more realistic model recognizing that all silicas are not created equal and should thus be considered in the plural as silicas and silica hybrids, which indeed hold various biocompatibility and biodegradability profiles. We then demonstrated that all silicas are-as displayed in Nature-degradable in water by dissolution, as governed by the laws of kinetics. Lastly, we explore the vast potential of tuning the degradability of silica by materials design using various silica hybrids for redox-, pH-, enzymatic-, and biochelation-mediated lysis mechanisms.

General synthesis of silica-based yolk/shell hybrid nanomaterials and in vivo tumor vasculature targeting

Multifunctional yolk/shell-structured hybrid nanomaterials have attracted increasing interest as theranostic nanoplatforms for cancer imaging and therapy. However, because of the lack of suitable surface engineering and tumor targeting strategies, previous research has focused mainly on nanostructure design and synthesis with few successful examples showing active tumor targeting after systemic administration. In this study, we report the general synthetic strategy of chelator-free zirconium-89 (⁸⁹Zr)-radiolabeled, TRC105 antibody-conjugated, silica-based yolk/shell hybrid nanoparticles for in vivo tumor vasculature targeting. Three types of inorganic nanoparticles with varying morphologies and sizes were selected as the internal cores, which were encapsulated into single hollow mesoporous silica nanoshells to form the yolk/shell-structured hybrid nanoparticles. As a proof-of-concept, we demonstrated successful surface functionalization of the nanoparticles with polyethylene glycol, TRC105 antibody (specific forCD105/endoglin), and ⁸⁹Zr (a positron-emitting radioisotope), and enhanced in vivo tumor vasculature-targeted positron emission tomography imaging in 4T1murine breast tumor-bearing mice. This strategy could be applied to the synthesis of other types of yolk/shell theranostic nanoparticles for tumor-targeted imaging and drug delivery.

Non-peptidic guanidinium-functionalized silica nanoparticles as selective mitochondria-targeting drug nanocarriers

We report on the design and fabrication of a Fe₃O₄ core-mesoporous silica nanoparticle shell (Fe₃O₄@MSNs)-based mitochondria-targeting drug nanocarrier. A guanidinium derivative (GA) was conjugated onto the Fe₃O₄@MSNs as the mitochondria-targeting ligand. The fabrication of the Fe₃O₄@MSNs and their functionalization with GA were carried out by the sol-gel polymerization of alkoxysilane groups. Doxorubicin (DOX), an anti-cancer drug, was loaded into the pores of a GA-attached Fe₃O₄@MSNs due to both its anti-cancer properties and to allow for the fluorescent visualization of the nanocarriers. The selective and efficient mitochondria-targeting ability of a DOX-loaded GA-Fe₃O₄@MSNs (DOX/GA-Fe₃O₄@MSNs) was demonstrated by a co-localization study, transmission electron microscopy, and a fluorometric analysis on isolated mitochondria. It was found that the DOX/GA-Fe₃O₄@MSNs selectively accumulated into mitochondria within only five minutes; to the best of our knowledge, this is the shortest accumulation time reported for mitochondria targeting systems. Moreover, 2.6 times higher amount of DOX was accumulated in mitochondria by DOX/GA-Fe₃O₄@MSNs than by DOX/TPP-Fe₃O₄@MSNs. A cell viability assay indicated that the DOX/GA-Fe₃O₄@MSNs have high cytotoxicity to cancer cells, whereas the GA-Fe₃O₄@MSNs without DOX are non-cytotoxic; this indicates that the DOX/GA-Fe₃O₄@MSNs have great potential for use as biocompatible and effective mitochondria-targeting nanocarriers for cancer therapy.

Hydrophobic interaction mediated coating of pluronics on mesoporous silica nanoparticle with stimuli responsiveness for cancer therapy

In this research, a novel method was used to successfully stably coat Pluronic P123 on mesoporous silica nanoparticles (MSNs). Co-constructing a drug delivery system (DDS) with P123 and MSNs has not been previously reported. In this DDS, the coating of P123 was realized through a hydrophobic interaction with octadecyl chain-modified MSNs. The experiments found only Pluronic with an appropriate ratio of hydrophilic and lipophilic segments could keep the nanoassemblies stable. For comparison, nanoassemblies consisting of P123 and octadecyl chain-modified MSNs with or without a disulfide bond were prepared, which were denoted as PSMSNs and PMSNs, respectively. The disulfide bond was expected to endow the system with redox-responsiveness to enhance the therapeutic effect meanwhile decreasing the toxicity. A series of experiments including characterization of the nanoparticles, in vitro drug release, cell uptake and cellular drug release, in vitro cytotoxicity, cell migration and biodistribution of the nanoparticles were carried out. Compared with the PMSNs, PSMSNs displayed a redox-responsive drug release property not only in in vitro release text, but also on the cellular level. In addition, the cell migration experiments proved that the coating of P123 endowed the system with the ability of anti-metastasis. The accumulation of P123 in the tumor was enhanced after coating the MSNs by virtue of the 'EPR' effect of nanoparticles compared with the solution form.

Biodistribution and biocompatibility of passion fruit-like nano-architectures in zebrafish

Passion fruit-like nano-architectures (NAs) are all-in-one platforms of increasing interest for the translation of metal nanoparticles into clinics. NAs are nature-inspired disassembling inorganic theranostics, which jointly combine most of the appealing behaviors of noble metal nanoparticles with their potential organism excretion. Despite their unique and promising properties, NAs in vivo interactions and potential adverse effects have not yet been investigated. In this study, we employ zebrafish (Danio Rerio) to assess the development toxicity of NAs as well as their uptake and bioaccumulation at different stages of growth. The evaluation of multiple endpoints related to the toxicity clearly indicates that NAs do not induce mortality, developmental defects, or alterations on the hatching rate and behavior of zebrafish. Moreover, the analysis of nanostructures uptake and biodistribution demonstrates that NAs are successfully internalized and present a specific localization. Overall, our results demonstrate that NAs are able to pass through the embryos chorion and accumulate in specific tissues, exhibiting an impressive biocompatibility.

Overcoming Chemoresistance in Cancer via Combined MicroRNA Therapeutics with Anticancer Drugs Using Multifunctional Magnetic Core-Shell Nanoparticles

In this study, we report the use of a multifunctional magnetic core-shell nanoparticle (MCNP), composed of a highly magnetic zinc-doped iron oxide (ZnFe₂O₄) core nanoparticle and a biocompatible mesoporous silica (mSi) shell, for the simultaneous delivery of let-7a microRNA (miRNA) and anticancer drugs (e.g., doxorubicin) to overcome chemoresistance in breast cancer. Owing to the ability of let-7a to repress DNA repair mechanisms (e.g., BRCA1 and BRCA2) and downregulate drug efflux pumps (e.g., ABCG2), delivery of let-7a could sensitize chemoresistant breast cancer cells (MDA-MB-231) to subsequent doxorubicin chemotherapy both in vitro and in vivo. Moreover, the multifunctionality of our MCNPs allows for the monitoring of in vivo delivery via magnetic resonance imaging. In short, we have developed a multifunctional MCNP-based therapeutic approach to provide an attractive method with which to enhance our ability not only to deliver combined miRNA therapeutics with small-molecule drugs in both selective and effective manner but also to sensitize cancer cells for the enhanced treatment via the combination of miRNA replacement therapy using a single nanoplatform.

Sol-gel Silica Nanoparticles in Medicine: A Natural Choice. Design, Synthesis and Products

Silica is one of the most abundant minerals in the Earth's crust, and over time it has been introduced first into human life and later into engineering. Silica is present in the food chain and in the human body. As a biomaterial, silica is widely used in dentistry, orthopedics, and dermatology. Recently amorphous sol-gel SiO₂ nanoparticles (NPs) have appeared as nanocarriers in a wide range of medical applications, namely in drug/gene target delivery and imaging diagnosis, where they stand out for their high biocompatibility, hydrophilicity, enormous flexibility for surface modification with a high payload capacity, and prolonged blood circulation time. The sol-gel process is an extremely versatile bottom-up methodology used in the synthesis of silica NPs, offering a great variety of chemical possibilities, such as high homogeneity and purity, along with full scale pH processing. By introducing organic functional groups or surfactants during the sol-gel process, ORMOSIL NPs or mesoporous NPs are produced. Colloidal route, biomimetic synthesis, solution route and template synthesis (the main sol-gel methods to produce monosized silica nanoparticles) are compared and discussed. This short review goes over some of the emerging approaches in the field of non-porous sol-gel silica NPs aiming at medical applications, centered on the syntheses processes used.

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.

Magnesium-Engineered Silica Framework for pH-Accelerated Biodegradation and DNAzyme-Triggered Chemotherapy

Inorganic nanocarriers have shown their high performance in disease theranostics in preclinical animal models and further great prospects for clinical translation. However, their dissatisfactory biodegradability and pre-drug leakage with nonspecificity to lesion sites significantly hinders the possible clinical translation. To solve these two critical issues, a framework-engineering strategy is introduced to simultaneously achieve enhanced biodegradability and controllable drug releasing, based on the mostly explored mesoporous silica-based nanosystems. The framework of mesoporous silica is engineered by direct Mg doping via a generic dissolution and regrowth approach, and it can transform into the easy biodegradation of magnesium silicate nanocarriers with simultaneous on-demand drug release. Such magnesium silicate nanocarriers can respond to the mild acidic environment of tumor tissue, causing the fast breaking up and biodegradation of the silica framework. More interesting, the released Mg²⁺ can further activate Mg²⁺ -dependent DNAzyme on the surface of hollow mesoporous magnesium silicate nanoparticles (HMMSNs) to cleave the RNA-based gatekeeper, which further accelerates the release of loaded anticancer drugs. Therefore, enhanced anticancer efficiency of chemotherapeutic drugs assisted by the biodegradable intelligent HMMSNs is achieved. The high biocompatibility of nanocarriers and biodegradation products is demonstrated and can be easily excreted via feces and urine guaranteeing their further clinical translation.

Low-Fouling and Biodegradable Protein-Based Particles for Thrombus Imaging

Nanomedicine holds great promise for vascular disease diagnosis and specific therapy, yet rapid sequestration by the mononuclear phagocytic system limits the efficacy of particle-based agents. The use of low-fouling polymers, such as poly(ethylene glycol), efficiently reduces this immune recognition, but these nondegradable polymers can accumulate in the human body and may cause adverse effects after prolonged use. Thus, new particle formulations combining stealth, low immunogenicity and biocompatible features are required to enable clinical use. Here, a low-fouling particle platform is described using exclusively protein material. A recombinant protein with superior hydrophilic characteristics provided by the amino acid repeat proline, alanine, and serine (PAS) is designed and cross-linked into particles with lysine (K) and polyglutamic acid (E) using mesoporous silica templating. The obtained PASKE particles have low-fouling behavior, have a prolonged circulation time compared to albumin-based particles, and are rapidly degraded in the cell's lysosomal compartment. When labeled with near-infrared fluorescent molecules and functionalized with an anti-glycoprotein IIb/IIIa single-chain antibody targeting activated platelets, the particles show potential as a noninvasive molecular imaging tool in a mouse model of carotid artery thrombosis. The PASKE particles constitute a promising biodegradable and versatile platform for molecular imaging of vascular diseases.

Hollow silica capsules for amphiphilic transport and sustained delivery of antibiotic and anticancer drugs

Hollow mesoporous silica capsules (HMSC) are potential drug transport vehicles due to their biocompatibility, high loading capacity and sufficient stability in biological milieu. Herein, we report the synthesis of ellipsoid-shaped HMSC (aspect ratio ∼2) performed using hematite particles as solid templates that were coated with a conformal silica shell through cross-condensation reactions. For obtaining hollow silica capsules, the iron oxide core was removed by acidic leaching. Gas sorption studies on HMSC revealed mesoscopic pores (main pore width ∼38 Å) and a high surface area of 308.8 m2 g-1. Cell uptake of dye-labeled HMSC was confirmed by incubating them with human cervical cancer (HeLa) cells and analyzing the internalization through confocal microscopy. The amphiphilic nature of HMSC for drug delivery applications was tested by loading antibiotic (ciprofloxacin) and anticancer (curcumin) compounds as model drugs for hydrophilic and hydrophobic therapeutics, respectively. The versatility of HMSC in transporting hydrophilic as well as hydrophobic drugs and a pH dependent drug release over several days under physiological conditions was demonstrated in both cases by UV-vis spectroscopy. Ciprofloxacin-loaded HMSC were additionally evaluated towards Gram negative (E. coli) bacteria and demonstrated their efficacy even at low concentrations (10 μg ml-1) in inhibiting complete bacterial growth over 18 hours.