Mesoporous Silica Nanoparticles as an Ideal Platform for Cancer Immunotherapy: Recent Advances and Future Directions

Cancer immunotherapy recently transforms the traditional approaches against various cancer malignancies. Immunotherapy includes systemic and local treatments to enhance immune responses against cancer and involves strategies such as immune checkpoints, cancer vaccines, immune modulatory agents, mimetic antigen-presenting cells, and adoptive cell therapy. Despite promising results, these approaches still suffer from several limitations including lack of precise delivery of immune-modulatory agents to the target cells and off-target toxicity, among others, that can be overcome using nanotechnology. Mesoporous silica nanoparticles (MSNs) are investigated to improve various aspects of cancer immunotherapy attributed to the advantageous structural features of this nanomaterial. MSNs can be engineered to alter their properties such as size, shape, porosity, surface functionality, and adjuvanticity. This review explores the immunological properties of MSNs and the use of MSNs as delivery vehicles for immune-adjuvants, vaccines, and mimetic antigen-presenting cells (APCs). The review also details the current strategies to remodel the tumor microenvironment to positively reciprocate toward the anti-tumor immune cells and the use of MSNs for immunotherapy in combination with other anti-tumor therapies including photodynamic/thermal therapies to enhance the therapeutic effect against cancer. Last, the present demands and future scenarios for the use of MSNs for cancer immunotherapy are discussed.

Recent advances in the development of poly(ester amide)s-based carriers for drug delivery

Biodegradable and biocompatible biomaterials have several important applications in drug delivery. The biomaterial family known as poly(ester amide)s (PEAs) has garnered considerable interest because it exhibits the benefits of both polyester and polyamide, as well as production from readily available raw ingredients and sophisticated synthesis techniques. Specifically, α-amino acid-based PEAs (AA-PEAs) are promising carriers because of their structural flexibility, biocompatibility, and biodegradability. Herein, we summarize the latest applications of PEAs in drug delivery systems, including antitumor, gene therapy, and protein drugs, and discuss the prospects of drug delivery based on PEAs, which provides a reference for designing safe and efficient drug delivery carriers.

Gold Nanoparticle-Loaded Silica Nanospheres for Sensitive and Selective Electrochemical Detection of Bisphenol A

In this work, silica nanospheres were used as support for gold nanoparticles and applied for bisphenol A electrochemical detection. The development of new silica-supported materials has attracted increasing attention in the scientific world. One approach of interest is using silica nanospheres as support for gold nanoparticles. These materials have a variety of applications in several areas, such as electrochemical sensors. The obtained materials were characterized by solid-state UV-vis spectroscopy, electron microscopy, X-ray diffraction, and electrochemical techniques. The electrode modified with AuSiO2700/CHI/Pt was applied as an electrochemical sensor for BPA, presenting an oxidation potential of 0.842 V and a higher peak current among the tested materials. The AuSiO2700/CHI/Pt electrode showed a logarithmic response for the detection of BPA in the range of 1-1000 nmol L-1, with a calculated detection limit of 7.75 nmol L-1 and a quantification limit of 25.8 nmol L-1. Thus, the electrode AuSiO2700/CHI/Pt was presented as a promising alternative to an electrochemical sensor in the detection of BPA.

Delivery of Natural Agents by Means of Mesoporous Silica Nanospheres as a Promising Anticancer Strategy

Natural prodrugs derived from different natural origins (e.g., medicinal plants, microbes, animals) have a long history in traditional medicine. They exhibit a broad range of pharmacological activities, including anticancer effects in vitro and in vivo. They have potential as safe, cost-effective treatments with few side effects, but are lacking in solubility, bioavailability, specific targeting and have short half-lives. These are barriers to clinical application. Nanomedicine has the potential to offer solutions to circumvent these limitations and allow the use of natural pro-drugs in cancer therapy. Mesoporous silica nanoparticles (MSNs) of various morphology have attracted considerable attention in the search for targeted drug delivery systems. MSNs are characterized by chemical stability, easy synthesis and functionalization, large surface area, tunable pore sizes and volumes, good biocompatibility, controlled drug release under different conditions, and high drug-loading capacity, enabling multifunctional purposes. In vivo pre-clinical evaluations, a significant majority of results indicate the safety profile of MSNs if they are synthesized in an optimized way. Here, we present an overview of synthesis methods, possible surface functionalization, cellular uptake, biodistribution, toxicity, loading strategies, delivery designs with controlled release, and cancer targeting and discuss the future of anticancer nanotechnology-based natural prodrug delivery systems.

Sodium alginate passivated CuInS2/ZnS QDs encapsulated in the mesoporous channels of amine modified SBA 15 with excellent photostability and biocompatibility

We herein report the synthesis of CuInS₂/ZnS (CIS/ZnS) quantum dots (QDs) via a greener method followed by sodium alginate (SA) passivation and encapsulation into mesoporous channels of amine modified silica (SBA15-NH₂) for improved photostability and biocompatibility. The as-synthesized CIS/ZnS QDs exhibited near infrared emission even after SA passivation and silica encapsulation. Transmission electron microscopy (TEM) and Small angle X-ray diffraction (XRD) revealed the mesoporous nature of the SBA-15 remained stable after loading with the SA-CIS/ZnS QDs. The effective encapsulation of SA-CIS/ZnS QDs inside the pores of SBA15-NH₂ matrix was confirmed by Brunauer-Emmett-Teller (BET) pore volume analysis while the interaction between the QDs and SBA15-NH₂ was confirmed using Fourier transform infrared (FTIR) spectroscopy. The photostability of the QDs was greatly enhanced after these modifications. The resultant SA-CIS/ZnS-SBA15-NH₂ (QDs-silica) composite possessed remarkable biocompatibility towards lung cancer (A549) and kidney (HEK 293) cell lines making it a versatile material for theranostic applications.

Rational design of yolk–shell nanostructures for drug delivery

The recent progress in yolk–shell nanoparticles (YSNPs) as a new class of hollow nanostructures applied for drug delivery.

Rational Design of Nanocarriers for Intracellular Protein Delivery

Protein/antibody therapeutics have exhibited the advantages of high specificity and activity even at an extremely low concentration compared to small molecule drugs. However, they are accompanied by unfavorable physicochemical properties such as fragile tertiary structure, large molecular size, and poor penetration of the membrane, and thus the clinical use of protein drugs is hindered by inefficient delivery of proteins into the host cells. To overcome the challenges associated with protein therapeutics and enhance their biopharmaceutical applications, various protein-loaded nanocarriers with desired functions, such as lipid nanocapsules, polymeric nanoparticles, inorganic nanoparticles, and peptides, are developed. In this review, the different strategies for intracellular delivery of proteins are comprehensively summarized. Their designed routes, mechanisms of action, and potential therapeutics in live cells or in vivo are discussed in detail. Furthermore, the perspective on the new generation of delivery systems toward the emerging area of protein-based therapeutics is presented as well.

Mesoporous Silica as a Versatile Platform for Cancer Immunotherapy

Immunotherapy has been recognized for decades as a promising therapeutic method for cancer treatment. To enhance host immune responses against cancer, antigen-presenting cells (APCs; e.g., dendritic cells) or T cells are educated using immunomodulatory agents including tumor-associated antigens and adjuvants, and manipulated to induce a cascading adaptive immune response targeting tumor cells. Mesoporous silica materials are promising candidates to improve cancer immunotherapy based on their attractive properties that include high porosity, high biocompatibility, facile surface modification, and self-adjuvanticity. Here, the recent progress on mesoporous-silica-based immunotherapies based on two material forms is summarized: 1) mesoporous silica nanoparticles (MSNs), which can be internalized into APCs, and 2) micrometer-sized mesoporous silica rods (MSRs) that can form a 3D space to recruit APCs. Subcutaneously injected MSN-based cancer vaccines can be taken up by peripheral APCs or by APCs in lymphoid organs to educate the immune system against cancer cells. MSR cancer vaccines can recruit immune cells into the MSR scaffold to induce cancer-specific immunity. Both vaccine systems successfully stimulate the adaptive immune response to eradicate cancer in vivo. Thus, mesoporous silica has potential value as a material platform for the treatment of cancer or infectious diseases.

A general soft-enveloping strategy in the templating synthesis of mesoporous metal nanostructures

Metal species have a relatively high mobility inside mesoporous silica; thus, it is difficult to introduce the metal precursors into silica mesopores and suppress the migration of metal species during a reduction process. Therefore, until now, the controlled growth of metal nanocrystals in a confined space, i.e., mesoporous channels, has been very challenging. Here, by using a soft-enveloping reaction at the interfaces of the solid, liquid, and solution phases, we successfully control the growth of metallic nanocrystals inside a mesoporous silica template. Diverse monodispersed nanostructures with well-defined sizes and shapes, including Ag nanowires, 3D mesoporous Au, AuAg alloys, Pt networks, and Au nanoparticle superlattices are successfully obtained. The 3D mesoporous AuAg networks exhibit enhanced catalytic activities in an electrochemical methanol oxidation reaction. The current soft-enveloping synthetic strategy offers a robust approach to synthesize diverse mesoporous metal nanostructures that can be utilized in catalysis, optics, and biomedicine applications.

Understanding the Effect of Surface Chemistry of Mesoporous Silica Nanorods on Their Vaccine Adjuvant Potency

Mesoporous silica nanoparticles are reported as adjuvants in nanovaccines in generating robust antigen-specific immunity. However, the effect of surface chemistry in initiating and modulating the immune response remains largely unexplored. In this study, mesoporous silica nanorods (MSNRs) are modified with NH₂ and C₁₈ groups to investigate the influence of surface functional groups (OH, NH₂ , and C₁₈ ) on their adjuvant efficacy. It is found that compared to OH and NH₂ groups, the hydrophobic C₁₈ modification significantly enhances antigen uptake by antigen presenting cells and endosomal-lysosomal escape in vitro, dendritic cells, and macrophages maturation ex vivo, and elicits secretion of interferon-γ level and antibody response in immunized mice. Moreover, bare MSNR and MSNRNH₂ exhibit T-helper 2 biased immune response, while MSNRC₁₈ shows a T-helper 1 biased immune response. These findings suggest that the surface chemistry of nanostructured adjuvants has profound impact on the immune response, which provides useful guidance for the design of effective nanomaterial based vaccines.

Large pore mesoporous silica nanomaterials for application in delivery of biomolecules

Various approaches for the synthesis of mesoporous silicate nanoparticles (MSN) with large pore (LP) diameters (in the range of 3-50 nm) are reviewed in this article. The work also covers the construction of magnetic analogues of large pore-mesoporous silica nanoparticles (LPMMSN) and their biomedical applications. The constructed materials exhibit vast potential for application in the loading and delivery of large drug molecules and biomolecules. Literature reports on the application of LPMSN and LPMMSN materials for the adsorption and delivery of proteins, enzymes, antibodies, and nucleic acids are covered in depth, which exemplify their highly potent characteristics for use in drug and biomolecule delivery to diseased tissues.

Vapour phase hydrogenation of phenol over rhodium on SBA-15 and SBA-16

In the present work, mesoporous SBA-15 and SBA-16 were synthesised using classical methods, and their physicochemical properties were investigated by X-ray diffraction (XRD), FTIR, TEM and N2 adsorption-desorption. Rhodium (Rh, 1 wt %) was loaded on the mesoporous SBA-15 and SBA-16 by an impregnation method. The Rh surface coverage, dispersion and crystallite size were determined by room temperature H2 chemisorption on reduced samples. The catalytic activity of Rh supported on mesoporous SBA-15 and SBA-16 was evaluated for the first time in the hydrogenation of phenol in vapour phase in a temperature range between 130 and 270 °C at atmospheric pressure. The reaction over Rh/SBA-15 at 180 °C produced cyclohexanone as the major product (about 60%) along with lower amounts of cyclohexanol (about 35%) and cyclohexane (about 15%). The influences of temperature, H2/phenol ratio, contact time and the nature of the solvent on the catalytic performance were systematically investigated. The Rh/SBA-16 system offered lower phenol conversion compared to Rh/SBA-15, but both have a very high selectivity for cyclohexanone (above 60%).