Biomedical applications of functionalized hollow mesoporous silica nanoparticles: focusing on molecular imaging

Evaluation of the Ocular Safety of Hollow Mesoporous Organosilica Nanoparticles with Different Tetrasulfur Bond Content

Background

Drug therapy for eye diseases has been limited by multiple protective mechanisms of the eye, which can be improved using well-designed drug delivery systems. Mesoporous silica nanoparticles (MSNs) had been used in many studies as carriers of therapeutic agents for ocular diseases treatment. However, no studies have focused on ocular biosafety. Considering that MSNs containing tetrasulfur bonds have unique advantages and have drawn increasing attention in drug delivery systems, it is necessary to explore the ocular biosafety of tetrasulfur bonds before their widespread application as ophthalmic drug carriers.

Methods

In this study, hollow mesoporous silica nanoparticles (HMSNs) with different tetrasulfur bond contents were prepared and characterized. The ocular biosafety of HMSN-E was evaluated in vitro on the three selected ocular cell lines, including corneal epithelial cells, lens epithelial cells and retinal endothelial cells (HREC), and in vivo by using topical eye drops and intravitreal injections.

Results

In cellular experiments, HMSNs caused obvious S content-dependent cytotoxic effect. HMSNs with the highest tetrasulfur bond content (HMSN-E), showed the highest cytotoxicity among all the HMSNs, and HREC was the most vulnerable cell to HMSN-E. It was shown that HMSN-E could react with intracellular GSH to generate H2S and decrease intracellular GSH concentration. Treatment of HREC with HMSN-E increased intracellular ROS, decreased mitochondrial membrane potential, and induced cell cycle arrest at the G1/S checkpoint, finally caused apoptosis and necrosis of HREC. Topical eye drops of HMSN-E could cause corneal damage. The intravitreal injection of HMSN-E could induce inflammation in the vitreum and ganglion cell layers, resulting in vitreous opacities and retinal abnormalities.

Conclusion

The incorporation of tetrasulfur bonds into HMSN can have toxic effects on ocular tissues. Therefore, when mesoporous silica nanocarriers are designed for ophthalmic pharmaceuticals, the ocular toxicity of the tetrasulfur bonds should be considered.

Effects of Different Surface Functionalizations of Silica Nanoparticles on Mesenchymal Stem Cells

Physicochemical properties of nanoparticles, such as particle size, surface charge, and particle shape, have a significant impact on cell activities. However, the effects of surface functionalization of nanoparticles with small chemical groups on stem cell behavior and function remain understudied. Herein, we incorporated different chemical functional groups (amino, DETA, hydroxyl, phosphate, and sulfonate with charges of +9.5, + 21.7, -14.1, -25.6, and -37.7, respectively) to the surface of inorganic silica nanoparticles. To trace their effects on mesenchymal stem cells (MSCs) of rat bone marrow, these functionalized silica nanoparticles were used to encapsulate Rhodamine B fluorophore dye. We found that surface functionalization with positively charged and short-chain chemical groups facilitates cell internalization and retention of nanoparticles in MSCs. The endocytic pathway differed among functionalized nanoparticles when tested with ion-channel inhibitors. Negatively charged nanoparticles mainly use lysosomal exocytosis to exit cells, while positively charged nanoparticles can undergo endosomal escape to avoid scavenging. The cytotoxic profiles of these functionalized silica nanoparticles are still within acceptable limits and tolerable. They exerted subtle effects on the actin cytoskeleton and migration ability. Last, phosphate-functionalized nanoparticles upregulate osteogenesis-related genes and induce osteoblast-like morphology, implying that it can direct MSCs lineage specification for bone tissue engineering. Our study provides insights into the rational design of biomaterials for effective drug delivery and regenerative medicine.

Stimuli-responsive biodegradable silica nanoparticles: From native structure designs to biological applications

Due to their inherent advantages, silica nanoparticles (SiNPs) have greatly potential applications as bioactive materials in biosensors/biomedicine. However, the long-term and nonspecific accumulation in healthy tissues may give rise to toxicity, thereby impeding their widespread clinical application. Hence, it is imperative and noteworthy to develop biodegradable and clearable SiNPs for biomedical purposes. Recently, the design of multi-stimuli responsive SiNPs to improve degradation efficiency under specific pathological conditions has increased their clinical trial potential as theranostic nanoplatform. This review comprehensively summaries the rational design and recent progress of biodegradable SiNPs under various internal and external stimuli for rapid in vivo degradation and clearance. In addition, the factors that affect the biodegradation of SiNPs are also discussed. We believe that this systematic review will offer profound stimulus and timely guide for further research in the field of SiNP-based nanosensors/nanomedicine.

Ultrasmall silica nanoparticles in translational biomedical research: Overview and outlook

The exemplary progress of silica nanotechnology has attracted extensive attention across a range of biomedical applications such as diagnostics and imaging, drug delivery, and therapy of cancer and other diseases. Ultrasmall silica nanoparticles (USNs) have emerged as a particularly promising class demonstrating unique properties that are especially suitable for and have shown great promise in translational and clinical biomedical research. In this review, we discuss synthetic strategies that allow precise engineering of USNs with excellent control over size and surface chemistry, functionalization, and pharmacokinetic and toxicological profiles. We summarize the current state-of-the-art in the biomedical applications of USNs with a particular focus on select clinical studies. Finally, we illustrate long-standing challenges in the translation of inorganic nanotechnology, particularly in the context of ultrasmall nanomedicines, and provide our perspectives on potential solutions and future opportunities in accelerating the translation and widespread adoption of USN technology in biomedical research.

Engineered Mesoporous Silica-Based Core-Shell Nanoarchitectures for Synergistic Chemo-Photodynamic Therapies

Combinatorial therapies have garnered enormous interest from researchers in efficiently devastating malignant tumors through synergistic effects. To explore the combinatorial approach, multiple therapeutic agents are typically loaded in the delivery vehicles, controlling their release profiles and executing subsequent therapeutic purposes. Herein, we report the fabrication of core (silica)-shell (mesoporous silica nanoparticles, MSNs) architectures to deliver methylene blue (MB) and cupric doxorubicin (Dox) as model drugs for synergistic photodynamic therapy (PDT), chemotherapy, and chemodynamic therapy (CDT). MB, as the photosensitizer, is initially loaded and stabilized in the silica core for efficient singlet oxygen generation under light irradiation towards PDT. The most outside shell with imidazole silane-modified MSNs is immobilized with a chemotherapeutic agent of Dox molecules through the metal (Copper, Cu)-ligand coordination interactions, achieving the pH-sensitive release and triggering the production of intracellular hydrogen peroxide and subsequent Fenton-like reaction-assisted Cu-catalyzed free radicals for CDT. Further, the designed architectures are systematically characterized using various physicochemical characterization techniques and demonstrate the potent anti-cancer efficacy against skin melanoma. Together our results demonstrated that the MSNs-based core-shell nanoarchitectures have great potential as an effective strategy in synergistically ablating cancer through chemo-, chemodynamic, and photodynamic therapies.

A review on the latest developments of mesoporous silica nanoparticles as a promising platform for diagnosis and treatment of cancer

Cancer is the second cause of human mortality after cardiovascular disease around the globe. Conventional cancer therapies are chemotherapy, radiation, and surgery. In fact, due to the lack of absolute specificity and high drug concentrations, early recognition and treatment of cancer with conventional approaches have become challenging issues in the world. To mitigate against the limitations of conventional cancer chemotherapy, nanomaterials have been developed. Nanomaterials exhibit particular properties that can overcome the drawbacks of conventional therapies such as lack of specificity, high drug concentrations, and adverse drug reactions. Among nanocarriers, mesoporous silica nanoparticles (MSNs) have gained increasing attention due to their well-defined pore size and structure, high surface area, good biocompatibility and biodegradability, ease of surface modification, and stable aqueous dispersions. This review highlights the current progress with the use of MSNs for the delivery of chemotherapeutic agents for the diagnosis and treatment of cancer. Various stimuli-responsive gatekeepers, which endow the MSNs with on-demand drug delivery, surface modification strategies for targeting purposes, and multifunctional MSNs utilized in drug delivery systems (DDSs) are also addressed. Also, the capability of MSNs as flexible imaging platforms is considered. In addition, physicochemical attributes of MSNs and their effects on cancer therapy with a particular focus on recent studies is emphasized. Moreover, major challenges to the use of MSNs for cancer therapy, biosafety and cytotoxicity aspects of MSNs are discussed.

Engineering mesoporous silica nanoparticles for drug delivery: where are we after two decades?

The present review details a chronological description of the events that took place during the development of mesoporous materials, their different synthetic routes and their use as drug delivery systems. The outstanding textural properties of these materials quickly inspired their translation to the nanoscale dimension leading to mesoporous silica nanoparticles (MSNs). The different aspects of introducing pharmaceutical agents into the pores of these nanocarriers, together with their possible biodistribution and clearance routes, would be described here. The development of smart nanocarriers that are able to release a high local concentration of the therapeutic cargo on-demand after the application of certain stimuli would be reviewed here, together with their ability to deliver the therapeutic cargo to precise locations in the body. The huge progress in the design and development of MSNs for biomedical applications, including the potential treatment of different diseases, during the last 20 years will be collated here, together with the required work that still needs to be done to achieve the clinical translation of these materials. This review was conceived to stand out from past reports since it aims to tell the story of the development of mesoporous materials and their use as drug delivery systems by some of the story makers, who could be considered to be among the pioneers in this area.

Covalently Attaching Hollow Silica Nanoparticles on a COC Surface for the Fabrication of a Three-Dimensional Protein Microarray

Compared to traditional two-dimensional (2D) biochips, three-dimensional (3D) biochips exhibit the advantages of higher probe density and detection sensitivity due to their designable surface microstructure as well as enlarged surface area. In the study, we proposed an approach to prepare a 3D protein chip by deposition of a monolayer of functionalized hollow silica nanoparticles (HSNs) on an activated cyclic olefin copolymer (COC) substrate. First, the COC substrate was chemically modified through the photografting technique to tether poly[3-(trimethoxysilyl) propyl methacrylate] (PTMSPMA) brushes on it. Then, a monolayer of HSNs was deposited on the modified COC and covalently attached via a condensation reaction between the hydrolyzed pendant siloxane groups of PTMSPMA and the Si-OH groups of HSNs. The roughness of the COC substrate significantly increased to 50.3 nm after depositing a monolayer of HSNs (ranging from 100 to 700 nm), while it only caused a negligible reduction in the light transmittance of COC. The HSN-modified COC was further functionalized with epoxide groups by a silane coupling agent for binding proteins. Immunoglobulin G could be effectively immobilized on this substrate with the highest immobilization efficiency of 75.2% and a maximum immobilization density of 1.236 μg/cm², while the highest immobilization efficiency on a 2D epoxide group-modified glass slide was only 57.4%. Moreover, immunoassay results confirmed a competitive limit of detection (LOD) (1.06 ng/mL) and a linear detection range (1-100 ng/mL) of the 3D protein chip. This facile and effective approach for fabricating nanoparticle-based 3D protein microarrays has great potential in the field of biorelated detection.

Development of local anesthetic drug delivery system by administration of organo-silica nanoformulations under ultrasound stimuli: in vitro and in vivo investigations

The development of local anesthetic (LA) system is the application of commercial drug for the pain management that indorses the reversible obstructive mechanism of neural transmission through preventing the innervation process in human peripheral nerves. Ropivacaine (RV) is one of the greatest frequently used LA s with the actions of long-lasting and low-toxicity for the post-operative pain management. In this work, we have approached novel design and development of glycosylated chitosan (GCS) encapsulated mesoporous silica nanoparticles (GCS-MONPs)-based nano-scaffold for sustainable distributions and controlled/supported arrival of stacked RV for targeting sites, which can be activated by either outer ultrasound activating to discharge the payload, foundation on-request and dependable analgesia. The structural and morphology analyses result established that prepared nano-formulations have successful molecular interactions and RV loaded spherical morphological structures. The drug release profile of developed nanostructure with ultrasound-activation has been achieved 50% of drug release in 2 h and 90% of drug release was achieved in 12 h, which displays more controlled release when compared to free RV solution. The in vitro cell compatibility analysis exhibited GCS-MONPs with RV has improved neuron cell survival rates when compared to other samples due to its porous surface and suitable biopolymer proportions. The analysis of ex vitro and in vivo pain relief analysis demonstrated treated animal models have high compatibility with GCS-MONPs@RV, which was confirmed by histomorphology. This developed MONPs based formulations with ultrasound-irradiation gives a prospective technique to clinical agony the board through on-request and dependable help with discomfort.

Fabrication, functionalization and advanced applications of magnetic hollow materials in confined catalysis and environmental remediation

Magnetic hollow-structured functional hybrid materials with unique architectures and preeminent properties have always been an area of extensive research. They represent a subtle collaboration of hollow architecture, mesoporous nanostructure and magnetic character. Owing to the merits of a large void space, low density, high specific surface area, well-defined active sites and facile magnetic recovery, these materials present promising application projections in numerous fields, such as drug delivery, adsorption, storage, catalysis and many others. In this review, recent progress in the design, synthesis, functionalization and applications of magnetic hollow-meso/nanostructured materials are discussed. The first part of the review has been dedicated to the preparation and functionalization of the materials. The synthetic protocols have been broadly classified into template-assisted and template-free methods and major trends in their synthesis have been elaborated in detail. Furthermore, the benefits and drawbacks of each method are compared. The later part summarizes the application aspects of confined catalysis in organic transformations and environmental remediation such as degradation of organic pollutants, dyes and antibiotics and adsorption of heavy metal ions. Finally, an outlook of future directions in this research field is highlighted.

A Comprehensive Study of Drug Loading in Hollow Mesoporous Silica Nanoparticles: Impacting Factors and Loading Efficiency

Although hollow mesoporous silica nanoparticles (HMSNs) have been intensively studied as nanocarriers, selecting the right HMSNs for specific drugs still remains challenging due to the enormous diversity in so far reported HMSNs and drugs. To this end, we herein made a comprehensive study on drug loading in HMSNs from the viewpoint of impacting factors and loading efficiency. Specifically, two types of HMSNs with negative and positive zeta potential were delicately constructed, and three categories of drugs were selected as delivery targets: highly hydrophobic and lipophobic (oily), hydrophobic, and hydrophilic. The results indicated that (i) oily drugs could be efficiently loaded into both of the two HMSNs, (ii) HMSNs were not good carriers for hydrophobic drugs, especially for planar drugs, (iii) HMSNs had high loading efficiency towards oppositely charged hydrophilic drugs, i.e., negatively charged HMSNs for cationic molecules and vice versa, (iv) entrapped drugs would alter zeta potential of drug-loaded HMSNs. This work may provide general guidelines about designing high-payload HMSNs by reference to the physicochemical property of drugs.

Silica-Based Nanoparticles as Drug Delivery Vehicles for Prostate Cancer Treatment

Prostate cancer (PCa) is one of the most commonly diagnosed cancers and is the fifth common cause of cancer-related mortality in men. Current methods for PCa treatment are insufficient owing to the challenges related to the non-specificity, instability and side effects caused by the drugs and therapy agents. These drawbacks can be mitigated by the design of a suitable drug delivery system that can ensure targeted delivery and minimise side effects. Silica based nanoparticles (SBNPs) have emerged as one of the most versatile materials for drug delivery due to their tunable porosities, high surface area and tremendous capacity to load various sizes and chemistry of drugs. This review gives a brief overview of the diagnosis and current treatment strategies for PCa outlining their existing challenges. It critically analyzes the design, development and application of pure, modified and hybrid SBNPs based drug delivery systems in the treatment of PCa, their advantages and limitations.

Glucosamine Modified the Surface of pH-Responsive Poly(2-(diethylamino)ethyl Methacrylate) Brushes Grafted on Hollow Mesoporous Silica Nanoparticles as Smart Nanocarrier

This work presents the synthesis of pH-responsive poly(2-(diethylamino) ethyl methacrylate) (PDEAEMA) brushes anchored on hollow mesoporous silica nanoparticles (HMSN-PDEAEMA) via a surface-initiated ARGET ATRP technique. The average size of HMSNs was ca. 340 nm, with a 90 nm mesoporous silica shell. The dry thickness of grafted PDEAEMA brushes was estimated to be ca 30 nm, as estimated by SEM and TEM. The halogen group on the surface of PDEAMA brushes was successfully derivatized with glucosamine, as confirmed by XPS. The effect of pH on the size of the hybrid nanoparticles was investigated by DLS. The size of fabricated nanoparticle decreased from ca. 950 nm in acidic media to ca. 500 nm in basic media due to the deprotonation of tertiary amine in the PDEAEMA. The PDEAEMA modified HMSNs nanocarrier was efficiently loaded with doxorubicin (DOX) with a loading capacity of ca. 64%. DOX was released in a relatively controlled pH-triggered manner from hybrid nanoparticles. The cytotoxicity studies demonstrated that DOX@HMSN-PDEAEMA-Glucosamine showed a strong ability to kill breast cancer cells (MCF-7 and MCF-7/ADR) at low drug concentrations, in comparison to free DOX.

Mesoporous Silica Nanoparticles as Theranostic Antitumoral Nanomedicines

Nanoparticles have become a powerful tool in oncology not only as carrier of the highly toxic chemotherapeutic drugs but also as imaging contrast agents that provide valuable information about the state of the disease and its progression. The enhanced permeation and retention effect for loaded nanocarriers in tumors allow substantial improvement of selectivity and safety of anticancer nanomedicines. Additionally, the possibility to design stimuli-responsive nanocarriers able to release their payload in response to specific stimuli provide an excellent control on the administered dosage. The aim of this review is not to present a comprehensive revision of the different theranostic mesoporous silica nanoparticles (MSN) which have been published in the recent years but just to describe a few selected examples to offer a panoramic view to the reader about the suitability and effectiveness of these nanocarriers in the oncology field.

Hydroxychloroquine-loaded hollow mesoporous silica nanoparticles for enhanced autophagy inhibition and radiation therapy

Radiotherapy (RT) is a major modality for cancer treatment, along with surgery and chemotherapy. Despite its therapeutic effect, the recurrence and metastasis of tumors due to the acquired resistance of cancer cells to RT remain significant clinical problems. Therefore, it is imperative to overcome radioresistance and improve radiosensitivity in cancer patients. Here, we synthesized hydroxychloroquine (HCQ)-loaded hollow mesoporous silica nanoparticles (HMSNs) to enable effective inhibition of radiation-induced cytoprotective autophagy and enhance the therapeutic efficacy of RT. HCQ-HMSN-treated HCT116 colon cancer cells showed a 200-fold higher intracellular uptake of HCQ than that of free HCQ-treated cells, thereby effectively inhibiting the radiation-induced autophagy of cancer cells. In vivo imaging and therapy studies of a tumor xenograft model showed preferential accumulation of HCQ-HMSNs in tumor tissues and significant enhancement of RT by inhibiting autophagy in the tumor sites. Histopathology analyses of major organs, blood chemistry profiles, and changes in body weights of mice confirmed the good biocompatibility of HCQ-HMSNs.

Synthesis of Colloidal Mesoporous Silica Spheres with Large Through-Holes on the Shell

Colloidal silica spheres with controllable large through-holes and mesopores on the shell were synthesized by using polystyrene (PS) spheres as a hard template and cationic surfactant hexadecyl trimethylammonium bromide (CTAB) as a soft template. Through modulating the synthetic conditions, including the volume ratio of ethanol (EtOH)/water, the amount of ammonia hydroxide, and the dosage of CTAB, SiO₂ spheres can transform among hollow structure, through-hole structure, and no large pore structure. The investigation suggests that the hydrolysis rate of the silica source and the interaction strength between the PS sphere template and SiO₂ may determine the large pore structure of the final product. The moderate hydrolysis rate of tetraethyl orthosilicate (TEOS) and strong interaction between the PS sphere template and SiO₂ is conductive to the formation of large through-holes in SiO₂ spheres. To further investigate the pore structure of through-holes of SiO₂ spheres, the lysozyme (Lz) was selected as a model molecule for adsorption experiments. The Lz adsorption experiments show that SiO₂ spheres with through-hole structure exhibit a much faster adsorption rate than SiO₂ spheres with hollow structure and higher adsorption capacity than SiO₂ with no large pore structure. Such a behavior could find interesting applications in the fields that require a fast-loading characteristic.

Loss of membrane asymmetry alters the interactions of erythrocytes with engineered silica nanoparticles

Disruption of plasma membrane integrity is a primary mechanism of nanoparticle toxicity in cells. Mechanistic studies on nanoparticle-induced membrane damage have been commonly performed using model membranes with a focus on symmetric bilayers, overlooking the fact that the membrane has an asymmetric phospholipid composition. In this study, erythrocytes with normal and scrambled membrane asymmetry were utilized to examine how the loss of membrane asymmetry and the resulting alterations in the outer leaflet lipid composition affect nanoparticle-membrane interactions. Unmodified, amine-modified, and carboxyl-modified silica (30 nm) were used as nanoparticle models. Loss of membrane asymmetry was achieved by induction of eryptosis, using a calcium ionophore. Erythrocyte membrane disruption (hemolysis) by unmodified silica nanoparticles was significantly reduced in eryptotic compared to healthy cells. Amine- and carboxyl-modified particles did not cause hemolysis in either cell. In agreement, a significant reduction in the binding of unmodified silica nanoparticles to the membrane was observed upon loss of membrane asymmetry. Unmodified silica particles also caused significant cell deformation, changing healthy erythrocytes into a spheroid shape. In agreement with findings in the cells, unmodified particles disrupted vesicles mimicking the erythrocyte outer leaflet lipid composition. The degree of disruption and nanoparticle binding to the membrane was reduced in vesicles mimicking the composition of scrambled membranes. Cryo-electron microscopy revealed the presence of lipid layers on particle surfaces, pointing to lipid adsorption as the mechanism for vesicle damage. Together, findings indicate an important role for the lipid composition of the membrane outer leaflet in nanoparticle-induced membrane damage in both vesicles and erythrocytes.

Multimodal Decorations of Mesoporous Silica Nanoparticles for Improved Cancer Therapy

The presence of leaky vasculature and the lack of lymphatic drainage of small structures by the solid tumors formulate nanoparticles as promising delivery vehicles in cancer therapy. In particular, among various nanoparticles, the mesoporous silica nanoparticles (MSN) exhibit numerous outstanding features, including mechanical thermal and chemical stability, huge surface area and ordered porous interior to store different anti-cancer therapeutics with high loading capacity and tunable release mechanisms. Furthermore, one can easily decorate the surface of MSN by attaching ligands for active targeting specifically to the cancer region exploiting overexpressed receptors. The controlled release of drugs to the disease site without any leakage to healthy tissues can be achieved by employing environment responsive gatekeepers for the end-capping of MSN. To achieve precise cancer chemotherapy, the most desired delivery system should possess high loading efficiency, site-specificity and capacity of controlled release. In this review we will focus on multimodal decorations of MSN, which is the most demanding ongoing approach related to MSN application in cancer therapy. Herein, we will report about the recently tried efforts for multimodal modifications of MSN, exploiting both the active targeting and stimuli responsive behavior simultaneously, along with individual targeted delivery and stimuli responsive cancer therapy using MSN.

The Engineering of Porous Silica and Hollow Silica Nanoparticles to Enhance Drug-loading Capacity

As a promising candidate for expanding the capacity of drug loading in silica nanoplatforms, hollow mesoporous silica nanoparticles (HMSNs) are gaining increasing attention. In this study, porous nanosilica (PNS) and HMSNs were prepared by the sol-gel method and template assisted method, then further used for Rhodamine (RhB) loading. To characterize the as-synthesized nanocarriers, a number of techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen absorption-desorption isotherms, dynamic light scattering (DLS), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) were employed. The size of HMSN nanoparticles in aqueous solution averaged 134.0 ± 0.3 nm, which could be adjusted by minor changes during synthesis, whereas that of PNS nanoparticles was 63.4 ± 0.6 nm. In addition, the encapsulation of RhB into HMSN nanoparticles to form RhB-loaded nanocarriers (RhB/HMSN) was successful, achieving high loading efficiency (51.67% ± 0.11%). This was significantly higher than that of RhB-loaded PNS (RhB/PNS) (12.24% ± 0.24%). Similarly, RhB/HMSN also possessed a higher RhB loading content (10.44% ± 0.02%) compared to RhB/PNS (2.90% ± 0.05%). From those results, it is suggested that prepared HMSN nanocarriers may act as high-capacity carriers in drug delivery applications.

Hollow Micro/Nanostructured Ceria-Based Materials: Synthetic Strategies and Versatile Applications

Hollow micro/nanostructured CeO₂ -based materials (HMNCMs) have triggered intensive attention as a result of their unique structural traits, which arise from their hollowness and the fascinating physicochemical properties of CeO₂ . This attention has led to widespread applications with improved performance. Herein, a comprehensive overview of methodologies applied for the synthesis of various hollow structures, such as hollow spheres, nanotubes, nanoboxes, and multishelled hollow spheres, is provided. The synthetic strategies toward CeO₂ hollow structures are classified into three major categories: 1) well-established template-assisted (hard-, soft-, and in situ template) methods; 2) newly emerging self-template approaches, including selective etching, Ostwald ripening, the Kirkendall effect, galvanic replacement, etc.; 3) bottom-up self-organized formation synthesis (namely, oriented attachment and self-deformation). Their underlying mechanisms are concisely described and discussed in detail, the differences and similarities of which are compared transversely and longitudinally. Niche applications of HMNCMs in a wide range of fields including catalysis, energy conversion and storage, sensors, absorbents, photoluminescence, and biomedicines are reviewed. Finally, an outlook of future opportunities and challenges in the synthesis and application of CeO₂ -based hollow structures is also presented.

Thermosensitive Biodegradable Copper Sulfide Nanoparticles for Real-Time Multispectral Optoacoustic Tomography

Although multifunctional inorganic nanoparticles have been extensively explored for effective cancer diagnosis and therapy, their clinical translation has been greatly impeded because of significant uptake in the reticuloendothelial system and concerns about potential toxicity. In this study, we uncovered the thermosensitive biodegradability of CuS nanoparticles, which have classically been considered as stable in bulk state. Polyethylene glycol (PEG)-coated CuS nanoparticles (CuS-PEG) were well preserved at 4 ºC but were rapidly degraded at 37 ºC within 1 week in both in vitro and in vivo tests. Furthermore, real-time multispectral optoacoustic tomography, which is more convenient and accurate than traditional ex vivo analysis, was successfully employed to noninvasively demonstrate the biodegradability of CuS-PEG nanoparticles and dynamically monitor their tumor imaging capacity. The temperature-dependent controllable degradation profile and excellent tumor retention of CuS-PEG nanoparticles endows them with great potential for clinical applications since it ensures that the nanoparticles remain intact during production, transportation, and storage but degrade and clear from the body at physiological temperature after accomplishing sufficient diagnosis and therapeutic operations.

Positron Emission Tomography/Magnetic Resonance Imaging of Glioblastoma Using a Functionalized Gadofullerene Nanoparticle

Water-soluble gadofullerene nanomaterials have been extensively investigated as magnetic resonance imaging (MRI) contrast agents, radical scavengers, sensitizers for photodynamic therapy, and inherent antineoplastic agents. Most recently, an alanine-modified gadofullerene nanoparticle (Gd@C₈₂-Ala) with excellent anticancer activity has been reported; however, the absolute tumor uptake of Gd@C₈₂-Ala is still far from being satisfactory, and its dynamic pharmacokinetics and long-term metabolic behaviors remain to be elucidated. Herein, Gd@C₈₂-Ala was chemically modified with eight-arm polyethylene glycol amine to improve its biocompatibility and provide the active sites for the attachment of a tumor-homing ligand (cRGD) and positron emission tomography (PET) isotopes (i.e., ⁶⁴Cu or ⁸⁹Zr). The physical and chemical properties (e.g., size, surface functionalization condition, radiochemical stability, etc.) of functionalized Gd@C₈₂-Ala were properly characterized. Also, its glioblastoma cell targeting capacity was evaluated in vitro by flow cytometry, confocal fluorescence microscopy, and dynamic cellular interaction assays. Because of the presence of gadolinium ions, the gadofullerene conjugates can act simultaneously as T₁* MRI contrast agents and PET probes. Thus, the pharmacokinetic behavior of functionalized Gd@C₈₂-Ala was investigated by PET/MRI, which combines the merits of high resolution and excellent sensitivity. The functionalized Gd@C₈₂-Ala-PEG-cRGD-NOTA-⁶⁴Cu (NOTA stands for 1,4,7-triazacyclononane-triacetic acid) demonstrated much higher accumulation in U87-MG tumor than its counterpart without cRGD attachment from in vivo PET observation, consistent with observation at the cellular level. In addition, Gd@C₈₂-Ala-PEG-Df-⁸⁹Zr (Df stands for desferrioxamine) was employed to investigate the metabolic behavior of gadofullerene conjugates in vivo for up to 30 days. It was estimated that nearly 70% of Gd@C₈₂-Ala-PEG-Df-⁸⁹Zr was excreted from the test subjects primarily through renal pathways within 24 h. With proper surface engineering, functionalized Gd@C₈₂-Ala nanoparticles can show an improved accumulation in glioblastoma. Pharmacokinetic studies also confirmed the safety of this nanoplatform, which can be used as an image-guidable therapeutic agent for glioblastoma.

Red Blood Cell Membrane Bioengineered Zr-89 Labelled Hollow Mesoporous Silica Nanosphere for Overcoming Phagocytosis

Biomimetic nanoparticles (NPs) have been actively studied for their biological compatibility due to its distinguished abilities viz. long-term circulation, low toxicity, ease for surface modification, and its ability to avoid phagocytosis of NPs by macrophages. Coating the NPs with a variety of cell membranes bearing the immune control proteins increases drug efficacy while complementing the intrinsic advantages of the NPs. In this study, efforts were made to introduce oxophilic radiometal 89Zr with hollow mesoporous silica nanospheres (HMSNs) having abundant silanol groups and were bioengineered with red blood cell membrane (Rm) having cluster of differentiation 47 (CD47) protein to evaluate its long-term in vivo behavior. We were successful in demonstrating the increased in vivo stability of synthesized Rm-camouflaged, 89Zr-labelled HMSNs with the markedly reduced 89Zr release. Rm camouflaged 89Zr-HMSNs effectively accumulated in the tumor by avoiding phagocytosis of macrophages. In addition, re-injecting the Rm isolated using the blood of the same animal helped to overcome the immune barrier. This novel strategy can be applied extensively to identify the long-term in vivo behavior of nano-drugs while enhancing their biocompatibility.

Biodegradable hybrid mesoporous silica nanoparticles for gene/chemo-synergetic therapy of breast cancer

Mesoporous silica nanoparticles have been extensively explored in anticancer nanomedicine due to their excellent biodegradability, which is one important focus in their further clinical translations. However, the traditional design concepts based on the functional modification with active groups cannot significantly improve the controlled drug release efficiency and anticancer effect. Herein, a molecularly organic–inorganic hybrid mesoporous silica nanoparticle (HMSN) nanocarrier coated with hyaluronic acid (HA) and polyethyleneimine (PEI) was constructed for the gene/chemo-synergetic therapy of breast cancer. Notably, HMSN with tumor-sensitive disulfide bond and targeting ligand HA can be decomposed when it encounters high concentration of glutathione (GSH) and hyaluronidase (HAase). The biodegradability of host molecules and the fast disintegration of the framework in tumor microenvironment can also accelerate the stimuli responsive release of cargos inside the pore space. Furthermore, the grafting of polyethyleneimine (PEI) could increase gene loading efficiency. From the above, the smart approach involves a combination of biodegradability and biological effect and results in synergetic antitumor effect of gene and chemical drug on breast cancer. All these findings demonstrated that HMSN/HA/PEI nanocarriers can be suitable for biomedical application, paving the way to fast development of multi-functional nano-biomedicine.

Comparison of high-performance liquid chromatography and ultraviolet-visible spectrophotometry to determine the best method to assess Levofloxacin released from mesoporous silica microspheres/nano-hydroxyapatite composite scaffolds

An assessment of Levofloxacin by high-performance liquid chromatography (HPLC) or ultraviolet-visible spectrophotometry (UV-Vis) and its pharmacokinetics in serum or plasma was made in a previous study by the present authors. Levofloxacin-loaded mesoporous silica microspheres/nano-hydroxyapatite (n-HA) composite scaffolds comprise a novel synthetic composite scaffold that may be utilized as a drug-delivery system for clinical usage. However, few studies have been published concerning a comparison of HPLC with UV-Vis, which is the preferred method for determination of Levofloxacin. In the present study, an HPLC method was first established, and subsequently a comparison of HPLC with the UV-Vis method was performed. The standard curve was established, and recovery rate from simulated body fluid was calculated. The linear concentration range for Levofloxacin was 0.05–300 µg/ml. The regression equation for HPLC was y=0.033x+0.010, with R²=0.9991, whereas that for UV-Vis was y=0.065x+0.017, with R²=0.9999. The recovery rates of low, medium and high (5, 25 and 50 µg/ml) concentrations of Levofloxacin determined by HPLC were 96.37±0.50, 110.96±0.23 and 104.79±0.06%, respectively, whereas those for low, medium and high concentrations according to UV-Vis were 96.00±2.00, 99.50±0.00 and 98.67±0.06%, respectively. Taken together, these findings demonstrated that it is not accurate to measure the concentration of drugs loaded on the biodegradable composite composites by UV-Vis. HPLC is the preferred method to evaluate sustained release characteristics of Levofloxacin released from mesoporous silica microspheres/n-HA composite scaffolds. The present study also provides guidance on which methods should be selected for investigating the sustained release properties of drugs in tissue engineering. The accurate determination of drug concentration in the drug delivery system provides guidance for the treatment of infectious diseases.

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.

Mesoporous silica nanoparticles as cutting-edge theranostics: Advancement from merely a carrier to tailor-made smart delivery platform

Large surface area, uniform and tunable pore size, high pore volume and low mass density- such attractive features of Mesoporous silica nanoparticles (MSNPs) have compelled researchers to explore the biomedical potential of this nano-material. Recently gained interest in MSNPs have been due to their tremendous potential in cancer therapy and imaging. Last several years have witnessed a rapid development in engineering functionalized MSNPs with various types of functional groups integrated into the system for imaging and therapeutic applications. Although their potential for drug delivery application has been studied since the year 2000, still a major challenge is to improve drug loading capacity and in vivo targeting with minimal side-effects to major organs. In this review article, the recent development of MSNPs as a therapeutic and diagnostic platform has been detailed out with emphasis on drug and bio-macromolecule delivery/co-delivery, bio-imaging and detoxification.

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.

Understanding the Connection between Nanoparticle Uptake and Cancer Treatment Efficacy using Mathematical Modeling

Nanoparticles have shown great promise in improving cancer treatment efficacy while reducing toxicity and treatment side effects. Predicting the treatment outcome for nanoparticle systems by measuring nanoparticle biodistribution has been challenging due to the commonly unmatched, heterogeneous distribution of nanoparticles relative to free drug distribution. We here present a proof-of-concept study that uses mathematical modeling together with experimentation to address this challenge. Individual mice with 4T1 breast cancer were treated with either nanoparticle-delivered or free doxorubicin, with results demonstrating improved cancer kill efficacy of doxorubicin loaded nanoparticles in comparison to free doxorubicin. We then developed a mathematical theory to render model predictions from measured nanoparticle biodistribution, as determined using graphite furnace atomic absorption. Model analysis finds that treatment efficacy increased exponentially with increased nanoparticle accumulation within the tumor, emphasizing the significance of developing new ways to optimize the delivery efficiency of nanoparticles to the tumor microenvironment.

Functional mesoporous silica nanoparticles for bio-imaging applications

Biomedical investigations using mesoporous silica nanoparticles (MSNs) have received significant attention because of their unique properties including controllable mesoporous structure, high specific surface area, large pore volume, and tunable particle size. These unique features make MSNs suitable for simultaneous diagnosis and therapy with unique advantages to encapsulate and load a variety of therapeutic agents, deliver these agents to the desired location, and release the drugs in a controlled manner. Among various clinical areas, nanomaterials-based bio-imaging techniques have advanced rapidly with the development of diverse functional nanoparticles. Due to the unique features of MSNs, an imaging agent supported by MSNs can be a promising system for developing targeted bio-imaging contrast agents with high structural stability and enhanced functionality that enable imaging of various modalities. Here, we review the recent achievements on the development of functional MSNs for bio-imaging applications, including optical imaging, magnetic resonance imaging (MRI), positron emission tomography (PET), computed tomography (CT), ultrasound imaging, and multimodal imaging for early diagnosis. With further improvement in noninvasive bio-imaging techniques, the MSN-supported imaging agent systems are expected to contribute to clinical applications in the future. This article is categorized under: Diagnostic Tools > In vivo Nanodiagnostics and Imaging Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

In Vivo Tumor-Targeted Dual-Modality PET/Optical Imaging with a Yolk/Shell-Structured Silica Nanosystem

Silica nanoparticles have been one of the most promising nanosystems for biomedical applications due to their facile surface chemistry and non-toxic nature. However, it is still challenging to effectively deliver them into tumor sites and noninvasively visualize their in vivo biodistribution with excellent sensitivity and accuracy for effective cancer diagnosis. In this study, we design a yolk/shell-structured silica nanosystem ⁶⁴Cu-NOTA-QD@HMSN-PEG-TRC105, which can be employed for tumor vasculature targeting and dual-modality PET/optical imaging, leading to superior targeting specificity, excellent imaging capability and more reliable diagnostic outcomes. By combining vasculature targeting, pH-sensitive drug delivery, and dual-modality imaging into a single platform, as-designed yolk/shell-structured silica nanosystems may be employed for the future image-guided tumor-targeted drug delivery, to further enable cancer theranostics.

Mesoporous Silica Nanoparticles

Integration of nanotechnology and biomedicine has offered great opportunities for the development of nanoscaled therapeutic platforms. Amongst various nanocarriers, mesoporous silica nanoparticles (MSNs) is one of the most developed and promising inorganic materials-based drug delivery system for clinical translations due to their simple composition and nanoporous structure. MSNs possess unique structural features, for example, well-defined morphology, large surface areas, uniform size, controllable structure, flexible pore volume, tunable pore sizes, extraordinarily high loading efficiency, and excellent biocompatibility. Progress in structure control and functionalization may endow MSNs with functionalities that enable medical applications of these integrated nanoparticles such as molecularly targeted drug delivery, multicomponent synergistic therapy, in vivo imaging and therapeutic capability, on-demand/stimuli-responsive drug release, etc. In this chapter, the authors overview MSNs' characteristics and the scientific efforts developed till date involving drug delivery and biomedical applications.

Mesoporous silica-based nanoplatforms for the delivery of photodynamic therapy agents

Photodynamic therapy (PDT) is an established method for the treatment of cancer which utilizes light, a photosensitizer (PS), and oxygen. Unfavourable characteristics of most PSs, such as low solubility and tumour specificity have led many researchers to adopt nanoscale drug delivery platforms for use in PDT. Mesoporous silica nanoparticles (MSNs) form a significant part of that effort, due to their ease and controllability of synthesis, ease of loading, availability of diverse surface functionalization, and biocompatibility. Therefore, in this review, we discuss the properties of MSNs as they pertain to their use in PDT and review the latest advances in the field, comparing the different approaches currently being used.

Quantitative and correlative biodistribution analysis of 89Zr-labeled mesoporous silica nanoparticles intravenously injected into tumor-bearing mice

The biodistribution of ⁸⁹Zr-labeled mesoporous silica nanoparticles (MSNs) was evaluated in detail using a prostate cancer mouse model bearing LNCaP C4-2 and PC-3 tumor xenografts with focus on passive targeting. PEGylation of radiolabeled MSNs significantly improved the blood circulation times and radically enhanced the accumulation in tumors comparable to the accumulation levels previously reported for similar but actively targeted particles. The distribution of the passively targeted MSNs was related to the degree of vascularization of the tumors and did not follow the trends observed in vitro. Correlative analyses of organ-to-blood ratios revealed that little or no accumulation of the particles is observed in the lungs, heart, and brain, and that the particles detected were present in the blood pool. On the other hand, clear accumulation was observed in the liver and spleen, in addition to the uptake in the tumors. The accumulation of particles in the kidney did not correlate with the MSN concentration in the blood, but indicated a rather steady level of particles in the kidney. The results, which partly contradict previous studies, highlight the importance of correlative analyses in order to evaluate the organ accumulation of particles.

Enhanced Fluorescence Imaging and Photodynamic Cancer Therapy Using Hollow Mesoporous Nanocontainers

Here we show that "off-on" type of photodynamic therapy agents could be developed using hollow mesoporous silica nanoparticles (HMSNPs), which can be used not only for enhancing delivery of photosensitizers to cancer cells but also for enabling switchable optical properties of the photosensitizers. Fluorescence and singlet oxygen generation of the photosensitizer-loaded HMSNP are turned off in its native state. In vitro cell studies showed that this HMSNP-based "off-on" agent may have potential utility in selective fluorescence detection and photodynamic therapy of cancers.

Human Hepatocarcinoma Cell Targeting by Glypican-3 Ligand Peptide Functionalized Silica Nanoparticles: Implications for Ultrasound Molecular Imaging

Silica nanoparticles (SiNPs) are widely studied nanomaterials for their potential employment in advanced biomedical applications, such as selective molecular imaging and targeted drug delivery. SiNPs are generally low cost and highly biocompatible, can be easily functionalized with a wide variety of functional ligands, and have been demonstrated to be effective in enhancing ultrasound contrast at clinical diagnostic frequencies. Therefore, SiNPs might be used as contrast agents in echographic imaging. In this work, we have developed a SiNPs-based system for the in vitro molecular imaging of hepatocellular carcinoma cells that express high levels of glypican-3 protein (GPC-3) on their surface. In this regard, a novel GPC-3 targeting peptide was designed and conjugated to fluorescent silica nanoparticles. The physicochemical properties, acoustic behavior, and biocompatibility profile of the functionalized SiNPs were characterized; then binding and uptake of both naked and functionalized SiNPs were analyzed by laser scanning confocal microscopy and transmission electron microscopy in GPC-3 positive HepG2 cells, a human hepatocarcinoma cell line. The results obtained showed that GPC-3-functionalized fluorescent SiNPs significantly enhanced the ultrasound contrast and were effectively bound and taken up by HepG2 cells without affecting their viability.

Indocyanine green-loaded hollow mesoporous silica nanoparticles as an activatable theranostic agent

Here we report indocyanine green (ICG)-loaded hollow mesoporous silica nanoparticles (ICG@HMSNP) as an activatable theranostic platform. Near-infrared fluorescence and singlet oxygen generation of ICG@HMSNP was effectively quenched (i.e. turned off) in its native state because of the fluorescence resonance energy transfer between ICG molecules. Therefore, ICG@HMSNP was nonfluorescent and nonphototoxic in the extracellular region. After the nanoparticles entered the cancer cells via endocytosis, they became highly fluorescent and phototoxic. In addition, intracellular uptake of ICG@HMSNP was 2.75 times higher than that of free ICG, resulting in an enhanced phototherapy of cancer.

Positron emission tomography and nanotechnology: A dynamic duo for cancer theranostics

Development of novel imaging probes for cancer diagnosis is critical for early disease detection and management. The past two decades have witnessed a surge in the development and evolution of radiolabeled nanoparticles as a new frontier in personalized cancer nanomedicine. The dynamic synergism of positron emission tomography (PET) and nanotechnology combines the sensitivity and quantitative nature of PET with the multifunctionality and tunability of nanomaterials, which can help overcome certain key challenges in the field. In this review, we discuss the recent advances in radionanomedicine, exemplifying the ability to tailor the physicochemical properties of nanomaterials to achieve optimal in vivo pharmacokinetics and targeted molecular imaging in living subjects. Innovations in development of facile and robust radiolabeling strategies and biomedical applications of such radionanoprobes in cancer theranostics are highlighted. Imminent issues in clinical translation of radiolabeled nanomaterials are also discussed, with emphasis on multidisciplinary efforts needed to quickly move these promising agents from bench to bedside.

Radiolabeled inorganic nanoparticles for positron emission tomography imaging of cancer: an overview

Over the last few years, a plethora of radiolabeled inorganic nanoparticles have been developed and evaluated for their potential use as probes in positron emission tomography (PET) imaging of a wide variety of cancers. Inorganic nanoparticles represent an emerging paradigm in molecular imaging probe design, allowing the incorporation of various imaging modalities, targeting ligands, and therapeutic payloads into a single vector. A major challenge in this endeavor is to develop disease-specific nanoparticles with facile and robust radiolabeling strategies. Also, the radiolabeled nanoparticles should demonstrate adequate in vitro and in vivo stability, enhanced sensitivity for detection of disease at an early stage, optimized in vivo pharmacokinetics for reduced non-specific organ uptake, and improved targeting for achieving high efficacy. Owing to these challenges and other technological and regulatory issues, only a single radiolabeled nanoparticle formulation, namely "C-dots" (Cornell dots), has found its way into clinical trials thus far. This review describes the available options for radiolabeling of nanoparticles and summarizes the recent developments in PET imaging of cancer in preclinical and clinical settings using radiolabeled nanoparticles as probes. The key considerations toward clinical translation of these novel PET imaging probes are discussed, which will be beneficial for advancement of the field.

Current Multistage Drug Delivery Systems Based on the Tumor Microenvironment

The development of traditional tumor-targeted drug delivery systems based on EPR effect and receptor-mediated endocytosis is very challenging probably because of the biological complexity of tumors as well as the limitations in the design of the functional nano-sized delivery systems. Recently, multistage drug delivery systems (Ms-DDS) triggered by various specific tumor microenvironment stimuli have emerged for tumor therapy and imaging. In response to the differences in the physiological blood circulation, tumor microenvironment, and intracellular environment, Ms-DDS can change their physicochemical properties (such as size, hydrophobicity, or zeta potential) to achieve deeper tumor penetration, enhanced cellular uptake, timely drug release, as well as effective endosomal escape. Based on these mechanisms, Ms-DDS could deliver maximum quantity of drugs to the therapeutic targets including tumor tissues, cells, and subcellular organelles and eventually exhibit the highest therapeutic efficacy. In this review, we expatiate on various responsive modes triggered by the tumor microenvironment stimuli, introduce recent advances in multistage nanoparticle systems, especially the multi-stimuli responsive delivery systems, and discuss their functions, effects, and prospects.

Chemo-photodynamic combined gene therapy and dual-modal cancer imaging achieved by pH-responsive alginate/chitosan multilayer-modified magnetic mesoporous silica nanocomposites

Novel nanocomposites were fabricated as theranostics for MR/CT imaging and tumor therapy in vivo.

Image-Guided Drug Delivery with Single-Photon Emission Computed Tomography: A Review of Literature

Tremendous resources are being invested all over the world for prevention, diagnosis, and treatment of various types of cancer. Successful cancer management depends on accurate diagnosis of the disease along with precise therapeutic protocol. The conventional systemic drug delivery approaches generally cannot completely remove the competent cancer cells without surpassing the toxicity limits to normal tissues. Therefore, development of efficient drug delivery systems holds prime importance in medicine and healthcare. Also, molecular imaging can play an increasingly important and revolutionizing role in disease management. Synergistic use of molecular imaging and targeted drug delivery approaches provides unique opportunities in a relatively new area called 'image-guided drug delivery' (IGDD). Single-photon emission computed tomography (SPECT) is the most widely used nuclear imaging modality in clinical context and is increasingly being used to guide targeted therapeutics. The innovations in material science have fueled the development of efficient drug carriers based on, polymers, liposomes, micelles, dendrimers, microparticles, nanoparticles, etc. Efficient utilization of these drug carriers along with SPECT imaging technology have the potential to transform patient care by personalizing therapy to the individual patient, lessening the invasiveness of conventional treatment procedures and rapidly monitoring the therapeutic efficacy. SPECT-IGDD is not only effective for the treatment of cancer but might also find utility in the management of several other diseases. Herein, we provide a concise overview of the latest advances in SPECT-IGDD procedures and discuss the challenges and opportunities for advancement of the field.