Redox-responsive mesoporous silica as carriers for controlled drug delivery: a comparative study based on silica and PEG gatekeepers

Potential Applications and Additive Manufacturing Technology-Based Considerations of Mesoporous Silica: A Review

Nanoporous materials are categorized as microporous (pore sizes 0.2-2 nm), mesoporous (pore sizes 2-50 nm), and macroporous (pore sizes 50-1000 nm). Mesoporous silica (MS) has gained a significant interest due to its notable characteristics, including organized pore networks, specific surface areas, and the ability to be integrated in a variety of morphologies. Recently, MS has been widely accepted by range of manufacturer and as drug carrier. Moreover, silica nanoparticles containing mesopores, also known as mesoporous silica nanoparticles (MSNs), have attracted widespread attention in additive manufacturing (AM). AM commonly known as three-dimensional printing is the formalized rapid prototyping (RP) technology. AM techniques, in comparison to conventional methods, aid in reducing the necessity for tooling and allow versatility in product and design customization. There are generally several types of AM processes reported including VAT polymerization (VP), powder bed fusion (PBF), sheet lamination (SL), material extrusion (ME), binder jetting (BJ), direct energy deposition (DED), and material jetting (MJ). Furthermore, AM techniques are utilized in fabrication of various classified fields such as architectural modeling, fuel cell manufacturing, lightweight machines, medical, and fabrication of drug delivery systems. The review concisely elaborates on applications of mesoporous silica as versatile material in fabrication of various AM-based pharmaceutical products with an elaboration on various AM techniques to reduce the knowledge gap.

Development of Surface Chemical Strategies for Synthesizing Redox-Responsive Diatomite Nanoparticles as a Green Platform for On-Demand Intracellular Release of an Antisense Peptide Nucleic Acid Anticancer Agent

Redox-responsive silica drug delivery systems are synthesized by aeco-friendly diatomite source to achieve on-demand release of peptide nucleic acid (PNA) in tumor reducing microenvironment, aiming to inhibit the immune checkpoint programmed cell death 1 receptor/programmed cell death receptor ligand 1 (PD-1/PD-L1) in cancer cells. The nanoparticles (NPs) are coated with polyethylene glycol chains as gatekeepers to improve their physicochemical properties and control drug release through the cleavable disulfide bonds (S-S) in a reductive environment. This study describes different chemical conditions to achieve the highest NPs' surface functionalization yield, exploring both multistep and one-pot chemical functionalization strategies. The best formulation is used for covalent PNA conjugation via the S-S bond reaching a loading degree of 306 ± 25 µg _PNA mg^-1 _DNPs . These systems are used for in vitro studies to evaluate the kinetic release, biocompatibility, cellular uptake, and activity on different cancer cells expressing high levels of PD-L1. The obtained results prove the safety of the NPs up to 200 µg mL^-1 and their advantage for controlling and enhancing the PNA intracellular release as well as antitumor activity. Moreover, the downregulation of PD-L1 observed only with MDA-MB-231 cancer cells paves the way for targeted immunotherapy.

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.

Recent Progress in Bio-Responsive Drug Delivery Systems for Tumor Therapy

Spatially- and/or temporally-controlled drug release has always been the pursuit of drug delivery systems (DDSs) to achieve the ideal therapeutic effect. The abnormal pathophysiological characteristics of the tumor microenvironment, including acidosis, overexpression of special enzymes, hypoxia, and high levels of ROS, GSH, and ATP, offer the possibility for the design of stimulus-responsive DDSs for controlled drug release to realize more efficient drug delivery and anti-tumor activity. With the help of these stimulus signals, responsive DDSs can realize controlled drug release more precisely within the local tumor site and decrease the injected dose and systemic toxicity. This review first describes the major pathophysiological characteristics of the tumor microenvironment, and highlights the recent cutting-edge advances in DDSs responding to the tumor pathophysiological environment for cancer therapy. Finally, the challenges and future directions of bio-responsive DDSs are discussed.

How Advancing are Mesoporous Silica Nanoparticles? A Comprehensive Review of the Literature

The application of mesoporous silica nanoparticles (MSNs) is ubiquitous in various sciences. MSNs possess unique features, including the diversity in manufacturing by different synthesis methods and from different sources, structure controllability, pore design capabilities, pore size tunability, nanoparticle size distribution adjustment, and the ability to create diverse functional groups on their surface. These characteristics have led to various types of MSNs as a unique system for drug delivery. In this review, first, the synthesis of MSNs by different methods via using different sources were studied. Then, the parameters affecting their physicochemical properties and functionalization have been discussed. Finally, the last decade's novel strategies, including surface functionalization, drug delivery, and cancer treatment, based on the MSNs in drug delivery and cancer therapy have been addressed.

Cancer-Targeted Chitosan-Biotin-Conjugated Mesoporous Silica Nanoparticles as Carriers of Zinc Complexes to Achieve Enhanced Chemotherapy In Vitro and In Vivo

Despite being the most common component of numerous metalloenzymes in the human body, zinc complexes are still under-rated as chemotherapeutic agents. Herein, the present study opens up a key route toward enhanced chemotherapy with the help of two Zn^II complexes (ZnMBC) synthesized alongside Mannich base ligands to upsurge biological potency. Further, well-established mesoporous silica nanoparticles (MSNs) have been chosen as carriers of the titled metallodrugs in order to achieve anticancer drug delivery. A pH-sensitive additive, namely, chitosan (CTS) conjugated with biotin is tagged to MSNs for the targeted release of core agents inside tumors selectively. In general, CTS blocks ZnMBC inside the mesopores of MSNs, and biotin acts as a targeting ligand to improve tumor-specific cellular uptake. CTS-biotin surface decoration significantly enhanced the cellular uptake of ZnMBC through endocytosis. A panel of four human cancer cell lines has revealed that ZnMBC (1/2)@MSNs-CTS-biotin nanoparticles (NPs) exhibits unprecedented enhanced cytotoxicity toward cancer cells with IC₅₀ values ranging from 6.5 to 28.8 μM through induction of apoptosis. NPs also possess great selectivity between normal and cancer cells despite this potency. Two-photon-excited in vitro imaging of normal (HEK) and cancer (HeLa) cells has been performed to confirm the biased drug delivery. Also, NP-induced apoptosis was found to be dependent on targeting DNA and ROS generation. Moreover, a lower range of LD₅₀ values (153.6-335.5 μM) were observed upon treatment zebrafish embryos with NPs in vivo. Because of the anatomical similarity to the human heart, the heart rate of NP-treated zebrafish has been analyzed in assessing the cardiac functions, which is in favor of the early clinical trials of ZnMBC (1/2)@MSNs-CTS-biotin candidates for their further evaluation as a chemotherapeutic and chemopreventive agent toward human cancers, especially adenocarcinoma.

Targeted combined therapy in 2D and 3D cultured MCF-7 cells using metformin and erlotinib-loaded mesoporous silica magnetic nanoparticles

AIM

This research aims to develop potential therapeutic nanostructures (NSs) encapsulating metformin (MET) and erlotinib (ER) for combinational therapy in breast cancer.

METHODS

The ER and MET, both were loaded on mesoporous silica magnetic nanoparticles conjugated with polyethylene glycol and methotrexate to achieve targeted NSs. The developed NSs were characterised using SEM, DLS, and FTIR. Afterward, MTT, Trypan blue, and DNA extraction assays were operated for biological evaluations in the 2D and 3D MCF-7 cells.

RESULTS

Physicochemical approaches indicated the mean diameter of 69.4 nm ± 9.5 (PDI = 0.64), and neutral charge (2 mv) for the developed NSs. MET and ER-loaded NSs exhibited 62.56% ± 4.41 and 67.73% ± 3.03 drug release amount in pH = 5.4, respectively. MTT assay revealed that ER- and MET-loaded NSs had less metabolic activity (≈ 20%) in comparison with non-targeted NSs.

CONCLUSION

Overall, our combined ER and MET-loaded targeted NSs result in a synergistic inhibitory impact on MCF-7 cells.

Application of Non-Viral Vectors in Drug Delivery and Gene Therapy

Vectors and carriers play an indispensable role in gene therapy and drug delivery. Non-viral vectors are widely developed and applied in clinical practice due to their low immunogenicity, good biocompatibility, easy synthesis and modification, and low cost of production. This review summarized a variety of non-viral vectors and carriers including polymers, liposomes, gold nanoparticles, mesoporous silica nanoparticles and carbon nanotubes from the aspects of physicochemical characteristics, synthesis methods, functional modifications, and research applications. Notably, non-viral vectors can enhance the absorption of cargos, prolong the circulation time, improve therapeutic effects, and provide targeted delivery. Additional studies focused on recent innovation of novel synthesis techniques for vector materials. We also elaborated on the problems and future research directions in the development of non-viral vectors, which provided a theoretical basis for their broad applications.

Relationship and improvement strategies between drug nanocarrier characteristics and hemocompatibility: What can we learn from the literature

This article discusses the various blood interactions that may occur with various types of nano drug-loading systems. Nanoparticles enter the blood circulation as foreign objects. On the one hand, they may cause a series of inflammatory reactions and immune reactions, resulting in the rapid elimination of immune cells and the reticuloendothelial system, affecting their durability in the blood circulation. On the other hand, the premise of the drug-carrying system to play a therapeutic role depends on whether they cause coagulation and platelet activation, the absence of hemolysis and the elimination of immune cells. For different forms of nano drug-carrying systems, we can find the characteristics, elements and coping strategies of adverse blood reactions that we can find in previous researches. These adverse reactions may include destruction of blood cells, abnormal coagulation system, abnormal effects of plasma proteins, abnormal blood cell behavior, adverse immune and inflammatory reactions, and excessive vascular stimulation. In order to provide help for future research and formulation work on the blood compatibility of nano drug carriers.

Preparation of Magnetic-Luminescent Bifunctional Rapeseed Pod-Like Drug Delivery System for Sequential Release of Dual Drugs

Drug delivery systems (DDSs) limited to a single function or single-drug loading are struggling to meet the requirements of clinical medical applications. It is of great significance to fabricate DDSs with multiple functions such as magnetic targeting or fluorescent labeling, as well as with multiple-drug loading for enhancing drug efficacy and accelerating actions. In this study, inspired by the dual-chamber structure of rapeseed pods, biomimetic magnetic–luminescent bifunctional drug delivery carriers (DDCs) of 1.9 ± 0.3 μm diameter and 19.6 ± 4.4 μm length for dual drug release were fabricated via double-needle electrospraying. Morphological images showed that the rapeseed pod-like DDCs had a rod-like morphology and Janus dual-chamber structure. Magnetic nanoparticles and luminescent materials were elaborately designed to be dispersed in two different chambers to endow the DDCs with excellent magnetic and luminescent properties. Synchronously, the Janus structure of DDCs promoted the luminescent intensity by at least threefold compared to single-chamber DDCs. The results of the hemolysis experiment and cytotoxicity assay suggested the great blood and cell compatibilities of DDCs. Further inspired by the core–shell structure of rapeseeds containing oil wrapped in rapeseed pods, DDCs were fabricated to carry benzimidazole molecules and doxorubicin@chitosan nanoparticles in different chambers, realizing the sequential release of benzimidazole within 12 h and of doxorubicin from day 3 to day 18. These rapeseed pod-like DDSs with excellent magnetic and luminescent properties and sequential release of dual drugs have potential for biomedical applications such as targeted drug delivery, bioimaging, and sustained treatment of diseases.

Cytotoxicity of mesoporous silica modified by amino and carboxyl groups on vascular endothelial cells

Mesoporous silica is widely used because of its unique and excellent properties, especially it can be used as a drug carrier and gene carrier in the biomedical field. After the mesoporous silica is put into clinical use, it is more likely to be exposed in human body. Therefore, the effect of mesoporous silica on human body cannot be ignored. The injury of vascular endothelial cells is a prerequisite for the occurrence of many cardiovascular diseases. As a drug and gene carrier, mesoporous silica increases its contact with vascular endothelial cells, so its toxic effect on cardiovascular system cannot be ignored. In this study, amino (NH₂ ) and carboxyl (COOH) were modified on mesoporous silica SBA-15 by post-grafting. The results showed that it still maintained the one-dimensional hexagonal mesoporous structure of SBA-15 and had typical mesoporous structure. Then human umbilical vein endothelial cells (HUVECs) were infected with SBA-15, NH₂ -SBA-15, and COOH-SBA-15. The results showed that the functionalized mesoporous silica SBA-15 had cytotoxicity to HUVECs and damaged the cell membrane, but compared with the unmodified mesoporous silica SBA-15 the cytotoxicity of functionalized mesoporous silica SBA-15 was lower and the toxicity of carboxyl modified group was the lowest. By comparing the cell inhibition rate and the expression level of lactate dehydrogenate and reactive oxygen species induced by the three materials, oxidative damage and cell membrane damage may be two mechanisms of cytotoxicity. Mesoporous silica SBA-15 has an effect on cardiovascular system by inducing the high expression of nitric oxide, intercellular adhesive molecule-1 and vascular cell adhesive molecule-1 in HUVECs. In summary, our results show that mesoporous silica is toxic to vascular endothelial cells.

Smart gating porous particles as new carriers for drug delivery

The design of smart drug delivery carriers has recently attracted great attention in the biomedical field. Smart carriers can specifically respond to physical and chemical changes in their environment, such as temperature, photoirradiation, ultrasound, magnetic field, pH, redox species, and biomolecules. This review summarizes recent advances in the integration of porous particles and stimuli-responsive gatekeepers for effective drug delivery. Their unique structural properties play an important role in facilitating the diffusion of drug molecules and cell attachment. Various techniques for fabricating porous materials, with their major advantages and limitations, are summarized. Smart gatekeepers provide advanced functions such as "open-close" switching by functionalized stimuli-responsive polymers on a particle's pores. These controlled delivery systems enable drugs to be targeted at specific rates, time programs, and sites of the human body. The gate structures, gating mechanisms, and controlled release mechanisms of each trigger are detailed. Current ongoing research and future trends in targeted drug delivery, tissue engineering, and regenerative medicine applications are highlighted.

Rational design of hollow mesoporous titania nanoparticles loaded with curcumin for UV-controlled release and targeted drug delivery

Curcumin (Cur), appeared to provide huge potential in biomedical application. However, its therapeutic efficacy was greatly limited as the result of poor solubility and instability. To address these limitations, we create a new type of hollow mesoporous titania nanoparticle (HMTN) to encapsulate Cur. HMTN was decorated with a layer of hydrophilic polyethylenimine (PEI), which controlled the release rate of Cur inside the pore due to its dendritic structure. Combined with the folic acid (FA) mediated targeting effect, the potential multifunctional Cur loaded titania nanoparticle (Cur-FA-PEI-HMTN) showed excellent biocompatibility and bioavailability, as well as the UV-responsive drug release properties. The operating parameters to prepare hollow structure were studied and the Cur-FA-PEI-HMTN nanosystem had been fully characterized by Brunauer-Emmet-Teller, Fourier transform infrared spectroscopy, transmission electron microscope, thermal gravity analysis, differential thermal analysis, x-ray diffraction, dynamic light scattering and zeta potential. In addition, the hemolytic test, as well as CCK8, flow cytometry, Hoechst 33342 staining experiment, were carried out to confirm the low cytotoxity and high biocompatibility. The confocal microscopy analysis results also revealed the increasing uptake of Cur@FA-PEI-HMTN by MCF-7 cells. The synthesized nanoparticles displayed great potential as drug nanovehicles with high biocompatibility.

Stimuli-responsive mesoporous silica nanoparticles: A custom-tailored next generation approach in cargo delivery

The pre-mature release of therapeutic cargos in the bloodstream or off-target sites is a major hurdle in drug delivery. However, stimuli-specific drug release responses are capable of providing greater control over the cargo release. Herein, various types of nanocarriers have been employed for such applications. Among various types of nanoparticles, mesoporous silica nanoparticles (MSNPs) have several attractive characteristics, such as high loading capacity, biocompatibility, small size, porous structure, high surface area, tunable pore size and ease of functionalization of the external and internal surfaces, which facilitates the entrapment and development of stimuli-dependent release of drugs. MSNPs could be modified with such stimuli-responsive entities like nucleic acid, peptides, polymers, organic molecules, etc., to prevent pre-mature cargo release, improving the therapeutic outcome. This controlled drug release system could be modulated to function upon extracellular or intracellular specific stimuli, including pH, enzyme, glucose, glutathione, light, temperature, etc., and thus provide minimal side effects at non-target sites. This system has great potential applications for the targeted delivery of therapeutics to treat clinically challenging diseases like cancer. This review summarizes the synthesis and design of stimuli-responsive release strategies of MSNP-based drug delivery systems along with investigations in biomedical applications.

Multi-stimuli responsive hollow MnO2-based drug delivery system for magnetic resonance imaging and combined chemo-chemodynamic cancer therapy

The exploration and application of hollow manganese dioxide nanoparticle (HMDN) for biosensing and biomedicine has gained significant research attention in the past decade. In this study, a type of biodegradable HMDN is prepared for multi-stimuli responsive tumor-targeted drug delivery, which was successfully loaded with doxorubicin hydrochloride (DOX). Then, the drug-loaded HMDN is functionalized with polyethyleneimine (PEI) as a gatekeeper followed by citraconic anhydride (cit) functionalized poly-_L-lysine (PLL(cit)) as a charge reversal moiety successively to yield the resultant DOX@HMDN-PEI-PLL(cit) nanoparticles. In vitro study showed that DOX@HMDN-PEI-PLL(cit) exhibited a ''stealthy'' property under physiological conditions and enhanced cellular uptake activity in response to the mild acidic tumor microenvironment due to the departure of cit. In vitro release profiles proved that the decomposition of HMDN to Mn²⁺ under acidic condition/high glutathione (GSH) concentration triggered the release of DOX and Fenton-like reaction for improved therapeutic effect. And Mn²⁺ could also act as a T₁-weighted magnetic resonance imaging (MRI) contrast agent. In vivo studies further proved with both the charge reversal and combined therapy properties, DOX@HMDN-PEI-PLL(cit) showed a good tumor enrichment ability and therapeutic effect with few side effects to the mice. These results demonstrate that DOX@HMDN-PEI-PLL(cit) nanoparticles are promising drug delivery systems for targeted cancer therapy. STATEMENT OF SIGNIFICANCE: Traditional chemotherapy based on anticancer drugs such as doxorubicin hydrochloride (DOX) shows limited efficacy with serious side effects. We employed hollow manganese dioxide nanoparticle (HMDN) to loaded DOX and coated it with polyethyleneimine and then citraconic anhydride functionalized poly-_L-lysine to endow it with a charge reversal property to obtain a multi-stimuli responsive drug delivery system named DOX@HMDN-PEI-PLL(cit). It was ''stealthy'' with low cellular uptake capability by normal cells, but could be "acid-activated" in tumors for endocytosis by cancer cells to reduce side effects. HMDN could be decomposed to Mn²⁺ under acidic conditions/high glutathione concentration to release DOX intracellular. DOX and Mn²⁺ catalyzed Fenton-like reaction could achieve a combined chemo-chemodynamic therapy. And Mn²⁺ could be used for T₁-weighted magnetic resonance imaging.

Superparamagnetic iron oxide nanoparticles functionalized with a binary alkoxysilane array and poly(4-vinylpyridine) for magnetic targeting and pH-responsive release of doxorubicin

The reported supramolecular arrangement offers an attractive strategy for the pH-sensitive and magnetically-guided release of doxorubicin, which could allow exploring novel therapeutic schemes against cancer.

Cellular uptake of self-emulsifying drug-delivery systems: polyethylene glycol versus polyglycerol surface

Aim: Comparison of the impact of polyethylene glycol (PEG) and polyglycerol (PG) surface decoration on self-emulsifying drug delivery system (SEDDS)-membrane interaction and cellular uptake. Materials & methods: PEG-, PEG/PG- and PG-SEDDS were assessed regarding their self-emulsifying properties, surface charge, bile salt fusibility, cellular uptake and interaction with endosome-mimicking membranes. Results: SEDDS exhibited droplet sizes between 150 and 175 nm, a narrow size distribution and self-emulsified within 7 min. Higher PEG-surfactant amounts in SEDDS resulted in charge-shielding and thus in a decrease of ζ potential up to Δ11 mV. The inert PEG-surface hampered bile salt fusion and interfered SEDDS-cell interaction. By reducing the PEG-surfactant amount to 10%, cellular uptake increased twofold compared with PEG-SEDDS containing 40% PEG-surfactant. PG-SEDDS containing no PEG-surfactants showed a threefold increased cellular uptake. Furthermore, complete replacement of PEG-surfactants by PG-surfactants led to enhanced cellular interaction and improved disruption endosome-like membranes. Conclusion: PG-surfactants demonstrated high potential to address PEG-surface associated drawbacks in SEDDS.

Folic acid modified lipid-bilayer coated mesoporous silica nanoparticles co-loading paclitaxel and tanshinone IIA for the treatment of acute promyelocytic leukemia

In this work, paclitaxel (Ptx) combined with tanshinone IIA (TanIIA) was found to show synergistic effect on inducing apoptosis of human acute promyelocytic leukemia (APL) cell line NB₄, and the anti-tumor effect was strongest when its molar ratio was 1:1. To enhance the efficacy and reduce side effects, an active targeting drug delivery system with mesoporous silica nanoparticles (MSNs) coated with folic acid (FA) modified PEGylated lipid-bilayer (LB) membrane (FA-LB-MSNs) was established for co-loading drugs. The drug loadings of Ptx and TanIIA in FA-LB-MSNs were 5.5% and 1.8%, respectively. Compared with the uncoated MSNs, the FA-LB-MSNs showed a sustained drug release, and Ptx and TanIIA released synchronously from the carriers. By means of biological adhesion between FA and its receptors, the uptake of FA-LB-MSNs by NB₄ cells was significantly higher than that of uncoated preparations, and Ptx combined with TanIIA had strong synergistic effect to enhance the apoptosis and differentiation of NB₄ cells. The results of pharmacodynamics in vivo showed that the FA-LB-MSNs targeted tumor in nude mice more effectively than the compared formulations without FA modification. The Ptx and TanIIA-loaded FA-LB-MSNs group showed significantly better effects on inducing apoptosis and inhibiting tumor growth than the reference groups, which agreed with the results of anti-tumor experiments in vitro. Furthermore, no toxicity was observed to the heart, liver, spleen, lung and kidney of the tumor-bearing animals, indicating good biocompatibility of the prepared novel nanocarriers. This study confirmed the synergistic therapeutic effect of Ptx and TanIIA on APL, and the superior of FA-LB-MSNs as co-loaded nanocarriers for active targeted therapy of tumors.

RhB-encapsulating silica nanoparticles modified with PEG impact the vascular endothelial function in endothelial cells and zebrafish model

Silica nanoparticles (SiNPs) have been widely used in human health related products, such as food additives, cosmetics and even drug delivery, gene therapy or bioimaging. Recently, a first-in-human clinical trial based on polyethylene glycol (PEG)-modified SiNPs had been approved by US FDA to trace melanoma. However, as a nano-based drug delivery system, its biocompatibility and vascular toxicity are still largely unknown. Thus, we synthesized the fluorescent SiNPs to explore the biocompatibility and vascular endothelial function, and compare different biological effects caused by PEG-modified and unmodified SiNPs in cells and zebrafish model. The characterizations of SiNPs and PEG-modified SiNPs were analyzed by TEM, SEM, AFM and DLS, which exhibited relatively good stable and dispersive. Compared with SiNPs, PEG-modified SiNPs had markedly reduced the inflammatory response and vascular damage in Tg (fli-1: EGFP) and Tg (mpo: GFP) transgenic zebrafish lines, respectively. Consistent with the in vivo results, the PEG-modified SiNPs had been found to significantly decline the levels of ROS, inflammatory cytokines and mitochondrial-mediated apoptosis in vascular endothelial cells compared to SiNPs, and the ROS scavenger NAC could effectively alleviate the above adverse effects induced by nanoparticles. Our results suggested that the PEG-modified SiNPs could become more safety via increasing the biocompatibility and decreasing cellular toxicities in living organisms.

Functionalized mesoporous silica nanoparticles in anticancer therapeutics

The application of nanomedicines in tumor targeting and attaining meaningful therapeutic benefits for the treatment of cancers has been going on for almost two decades. Beyond the lipidic and polymeric nanomedicines-based passive and active targeting, the quest for inventing the new generation of carriers has no end. This has lead to the evolution of some of the unique carrier systems with supramolecular assembly structures. Mesoporous nanoparticulate systems (MSNPs) are the recently explored substances with favorable potential for drug delivery and drug targeting applications especially in cancer chemotherapeutics. Notwithstanding their physical properties that makes them a suitable carrier for cancer treatment, but their outstanding ability towards chemical functionalization helps in delivering the imaging agents for diagnostic applications. MSNPs can improve the dissolution rate and systemic availability of the poorly water soluble drugs due to their mesoporous structures. Besides, guest molecules including targeting ligands, biomimetic agents, fluorescent dyes, and biocompatible polymers can be efficiently encapsulated in their tunable porous structure for targeting purpose. Some special features of the MSNPs which make them one of the highly effective nanocarrier systems include their ability to encapsulate non-crystalline drugs in their mesopores, high dispersion ability as a function of large surface area and wetting properties. For anticancer drug delivery, MSNPs are worthful to provide excellent drug loading capacity and endocytotic behavior. Moreover, the external surface of MSNPs can be precisely modified for tumor-recognition and developing sensitivity of the antitumor agents towards the cancer cells. Owing to the innumerable applications of MSNPs till now in cancer treatment, the present article particularly focuses to provide an overview account with complete details on the topic to make the readers abreast with details on physiochemical and material properties of MSNPs, their applications and current innovations for the purpose.

DePEGylation strategies to increase cancer nanomedicine efficacy

To maximize drug targeting to solid tumors, cancer nanomedicines with prolonged circulation times are required. To this end, poly(ethylene glycol) (PEG) has been widely used as a steric shield of nanomedicine surfaces to minimize serum protein absorption (opsonisation) and subsequent recognition and clearance by cells of the mononuclear phagocyte system (MPS). However, PEG also inhibits interactions of nanomedicines with target cancer cells, limiting the effective drug dose that can be reached within the target tumor. To overcome this dilemma, nanomedicines with stimuli-responsive cleavable PEG functionality have been developed. These benefit from both long circulation lifetimes en route to the targeted tumor as well as efficient drug delivery to target cancer cells. In this review, various stimuli-responsive strategies to dePEGylate nanomedicines within the tumor microenvironment will be critically reviewed.

NIR-triggered release of DOX from sophorolipid-coated mesoporous carbon nanoparticles with the phase-change material 1-tetradecanol to treat MCF-7/ADR cells

To prevent premature drug release from nanoparticles, it is vital to design and prepare controlled and site-specific drug release systems.

Folate-targeting and bovine serum albumin-gated mesoporous silica nanoparticles as a redox-responsive carrier for epirubicin release

A targeted DDS with covalently conjugated BSA and folate for GSH-triggered drug release and recognition of FR-positive cancer cells.

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.

Redox-responsive Drug Delivery Systems

Disbalanced reactive oxygen species (ROS) and glutathione (GSH) are characteristic features of tumor cells. High intracellular GSH concentration in tumor cells is a well-documented fact that leads to a very high reducing intracellular bio-milieu. High accumulation of ROS is known to occur in almost all cancers and can act as a two-edged sword during tumor development, by either promoting or inhibiting growth. These two features present unique opportunities to design drug delivery systems that are responsive to reduction or/and oxidation stimuli and has attracted accrued interest from researchers. These nanocarriers change their structural integrity, either through disassembly or degradation, to deliver their payload in the presence of the trigger. The aim of this chapter is to summarize the key developments in the design of materials with redox-responsive behaviour and their subsequent application in the field of nanomedicine targeting cancer. Strategies into exploiting both stimuli in a single nano drug delivery system to enhance therapeutic efficacy are also addressed.

Study on the formation and properties of red blood cell-like Fe3O4/TbLa3(Bim)12/PLGA composite particles

Besides the particle size and surface performance, the shape also plays a key role in drug delivery systems. Red blood cells are the most abundant blood cells in the human body, and are excellent oxygen carriers, due to their unique biconcave discoid shape. In this study, red blood cell (RBC)-like Fe3O4/TbLa3(Bim)12/poly(lactic-co-glycolic acid) (PLGA) composite particles, with magnetic response and bioimaging functions, were prepared by electrospraying. Various electrospraying parameters, such as solvent, PLGA concentration, collecting distance and solution flow rate were investigated in detail to attempt to obtain RBC-like composite particles. The size distribution, morphology, structure, and hydrophobicity-hydrophilicity of particles were characterized. The results revealed the RBC-like Fe3O4/TbLa3(Bim)12/PLGA composite particles exhibited a strong green fluorescence and good magnetic behavior even when incubated with cells. Furthermore, the intensity of the magnetization and fluorescence can be adjusted by changing the contents of Fe3O4 and TbLa3(Bim)12. The effect on cell viability of the RBC-like Fe3O4/TbLa3(Bim)12/PLGA composite particles was evaluated in A549 cells and RBCs, and it was determined to have low cytotoxicity and excellent blood biocompatibility, suggesting that it is a promising candidate for application in drug delivery, targeting and tracking.

Efficient Self-Assembly of mPEG End-Capped Porous Silica as a Redox-Sensitive Nanocarrier for Controlled Doxorubicin Delivery

Porous nanosilica (PNS) has been regarded as a promising candidate for controlled delivery of anticancer drugs. Unmodified PNS-based nanocarriers, however, showed a burst release of encapsulated drugs, which may limit their clinical uses. In this report, PNS was surface conjugated with adamantylamine (ADA) via disulfide bridges (-SS-), PNS-SS-ADA, which was further modified with cyclodextrin-poly(ethylene glycol) methyl ether conjugate (CD-mPEG) to form a core@shell structure PNS-SS-ADA@CD-mPEG for redox triggered delivery of doxorubicin (DOX), DOX/PNS-SS-ADA@CD-mPEG. The prepared PNS-SS-ADA@CD-mPEG nanoparticles were spherical in shape with an average diameter of 55.5 ± 3.05 nm, a little larger than their parentally PNS nanocarriers, at 49.6 ± 2.56 nm. In addition, these nanoparticles possessed high drug loading capacity, at 79.2 ± 3.2%, for controlled release. The release of DOX from DOX/PNS-SS-ADA@CD-mPEG nanoparticles was controlled and prolonged up to 120 h in PBS medium (pH 7.4), compared to less than 40 h under reducing condition of 5 mM DTT. Notably, the PNS-SS-ADA@CD-mPEG was a biocompatible nanocarrier, and the toxicity of DOX was dramatically reduced after loading drugs into the porous core. This redox-sensitive PNS-SS-ADA@CD-mPEG nanoparticle could be considered a potential candidate with high drug loading capacity and a lower risk of systemic toxicity.

pH sensitive chitosan-mesoporous silica nanoparticles for targeted delivery of a ruthenium complex with enhanced anticancer effects

Nanocarriers are widely used for delivering drugs to tumors and their development is progressing steadily. In this study, a pH sensitive mesoporous silica nanocarrier, RuNHC@MSNs-CTS-Biotin (CTS = chitosan), is developed for the targeted delivery and controlled release of a ruthenium(ii) N-heterocyclic carbene (RuNHC) complex. The RuNHC@MSNs-CTS-Biotin nanoparticles were composed of RuNHC loaded mesoporous silica nanoparticles (MSNs) coated with chitosan-biotin (CTS-Biotin) conjugates. CTS traps the RuNHC complex inside the mesopores and biotin is used as a targeting ligand to improve specific cell uptake. The particle size of RuNHC@MSNs-CTS-Biotin was around 90 nm with a zeta potential of 12.0 mV and the RuNHC loading capacity was 26.31%. The release of RuNHC from RuNHC@MSNs-CTS-Biotin was in a pH-dependent manner, and it exhibited a 59.71% terminal release ratio at pH 5.0, but almost no release under neutral conditions (pH 7.4). Its in vitro cellular uptake and anticancer activity revealed that RuNHC@MSNs-CTS-Biotin could be selectively internalized in cancer cells by biotin receptor-mediated endocytosis and this resulted in a significant improvement in anticancer activities as compared with the RuNHC complex. This multifunctional nanocarrier system provides a promising platform for the development of precisely controllable cancer therapy.

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.

NIR light-activated dual-modality cancer therapy mediated by photochemical internalization of porous nanocarriers with tethered lipid bilayers

To overcome endo/lysosomal restriction as well as to increase the clinical availability of nanomedicine, we report on a NIR stimuli-responsive nanoplatform based on mesoporous silica nanoparticles tethered with lipid bilayers (MSN@tLB) for chemotherapy and photodynamic dual-modality therapy. In this nanosystem, a hydrophilic drug molecule zoledronic acid (ZOL) was first incorporated into the MSN core with modifications of hyperbranched polyethylenimine (PEI). To prevent the leakage of the payload, the LB shell was covalently tethered onto the MSN core via the PEI cushion which can greatly enhance the stability of the LB. Meanwhile, a hydrophobic photosensitizer IR-780 iodide was introduced into the hydrophobic compartment to endow the system with photo-activation properties. The as-prepared MSN-ZOL@tLB-IR780 possesses high dispersion stability stemming from the LB, as well as negligible cytotoxicity. After cellular internalization and endo/lysosomal capture of the nanoparticles, photochemical internalization (PCI) mediated simultaneous cargo release and endo/lysosomal escape were achieved by local ROS production upon 808 nm irradiation, thus leading to highly efficient chemo-photodynamic therapy on cancer cells in vitro. Such a system presents a sophisticated platform that integrates biocompatibility, spatiotemporal control, NIR-responsiveness, and synergistic therapies to promote cancer therapy.

Hybrid mesoporous silica nanocarriers with thermovalve-regulated controlled release

Mesoporous silica nanoparticles (MSNs) are excellent nanocarriers, featuring very high cargo capacity due to their large surface area and pore volume. The particle and pore dimensions can be accurately tuned, and both the internal and external surfaces allow versatile functionalization. We developed hybrid MSNs with diameters around 140 nm, with the external surface selectively modified with a temperature-responsive biocompatible copolymer to control cargo release. The nanoparticles feature either a polymer brush or a gel-like responsive shell, produced by grafting from RAFT polymerization of PEG-acrylate macromonomers. The hybrid nanoparticles have fluorescent molecules incorporated into the inorganic network providing excellent optical properties for traceability and imaging. The cargo release profiles are explained by a temperature-controlled "pumping" mechanism: at low temperature (ca. 20 °C) the polymer shell is hydrophilic and expanded, opposing cargo diffusion out of the shell and retaining the molecules released from the mesopores; above room temperature (ca. 40-50 °C) the polymer network becomes more hydrophobic and collapses onto the silica surface, releasing the cargo by a sponge-like squeezing effect. The release kinetics depends on the polymer shell type, with better results obtained for the gel-coated nanoparticles. Our proof-of-concept system shows that by modulating the temperature, it is possible to achieve a pumping regime that increases the release rate in a controlled way.

Superiority of amino-modified chiral mesoporous silica nanoparticles in delivering indometacin

The present study established indometacin (IMC) delivery system with chiral mesoporous silica nanoparticles (CMSNs) and amino-modified chiral mesoporous silica nanoparticles (Amino-CMSNs) that previously reported as pharmaceutical excipients, and their systemic biological effects, mainly consisting of in vitro drug intestinal permeability, haemolysis assay, in vivo pharmacokinetics, anti-inflammation pharmacodynamics and gastric irritation, were addressed. It turned out that the two IMC delivery systems established by CMSN and Amino-CMSN significantly improved drug intestinal permeability due to the improved drug dissolution caused by conversion of drug crystalline state to amorphous phase. Further, IMC-loaded Amino-CMSN was the superior choice because of its higher dissolution rate. Furthermore, CMSN and Amino-CMSN were safe to be circulated in blood, and Amino-CMSN with significant lower haemolysis ratio than CMSN was better for the minimum haemolytic behaviour. Oral bioavailability and anti-inflammation effect of IMC delivery systems established by CMSN and Amino-CMSN were enhanced compared with IMC, which was attributed to the primary cause of the improvement of IMC dissolution, and Amino-CMSN exhibited better biological effect. As a result of these facts, it is believed that the effective delivery of IMC by Amino-CMSN will provide a new candidate to formulate poorly soluble drugs so as to significantly develop pharmaceutical application.

Multifunctional Peptide-Amphiphile End-Capped Mesoporous Silica Nanoparticles for Tumor Targeting Drug Delivery

A tumor targeting redox-responsive drug delivery system (DDS) with bioactive surface was constructed by immobilizing peptide-based amphiphile C12-CGRKKRRQRRRPPQRGDS (defined as ADDA-TCPP) onto the mesoporous silica nanoparticles (MSNs) as an end-capping nanovalve, which consists of two main segments: a hydrophobic alkyl chain ADDA and a hydrophilic amino acid sequence containing a Tat_48-60 peptide sequence with a thiol terminal group and an RGDS targeting ligand, via a disulfide linkage for redox-triggered intracellular drug delivery. A series of characterizations confirmed that the nanosystem had been successfully fabricated. The antitumor drug doxorubicin (DOX) was selected as a model drug and efficiently trapped in the pores of MSNs, and an in vitro release experiment demonstrated that the mesopores of the resulting DOX-loaded MSNs (DOX@MSN-ss-ADDA-TCPP) could be sealed tightly with ADDA-TCPP self-assemblies through hydrophobic interactions between the alkyl chains; the resulting DDS exhibited "zero premature release" of DOX in the physical environment. However, a burst drug release was triggered by a high concentration of glutathione (GSH) in simulated cellular cytosol. Moreover, detailed investigations confirmed that incorporation of RGDS peptide facilitated the active targeting delivery of DOX to α_vβ₃ integrin overexpressed tumor cells, and Tat_48-60 modification on MSNs could enhance intracellular drug delivery, exhibiting an obvious toxicity to tumor cells. The multifunctional nanosystem constructed here can realize the controlled drug release and serve as a platform for designing multifunctional nanocarriers using diversified bioactive peptide-based amphiphile.