Zn- and Mg- containing tricalcium phosphates-based adjuvants for cancer immunotherapy

Bioactive mesoporous silica materials-assisted cancer immunotherapy

Immunotherapy is initially envisioned as a powerful approach to train immune cells within the tumor microenvironment (TME) and lymphoid tissues to elicit strong anti-tumor responses. However, clinical cancer immunotherapy still faces challenges, such as limited immunogenicity and insufficient immune response. Leveraging the advantages of mesoporous silica (MS) materials in controllable drug and immunomodulator release, recent efforts have focused on engineering MS with intrinsic immunoregulatory functions to promote robust, systemic, and safe anti-tumor responses. This review discusses advances in bioactive MS materials that address the challenges of immunotherapy. Beyond their role in on-demand delivery and drug release in response to the TME, we highlight the intrinsic functions of bioactive MS in orchestrating localized immune responses by inducing immunogenic cell death in tumor cells, modulating immune cell activity, and facilitating tumor-immune cell interactions. Additionally, we emphasize the advantages of bioactive MS in recruiting and activating immune cells within lymphoid tissues to initiate anti-tumor vaccination. The review also covers the challenges of MS-assisted immunotherapy, potential solutions, and future outlooks. With a deeper understanding of material-bio interactions, the rational design of MS with sophisticated bioactivities and controllable responsiveness holds great promise for enhancing the outcomes of personalized immunotherapy.

3D nanocomposites of β-TCP-H3BO3-Cu with improved mechanical and biological performances for bone regeneration applications

Recently, 3-D porous architecture of the composites play a key role in cell proliferation, bone regeneration, and anticancer activities. The osteoinductive and osteoconductive properties of β-TCP allow for the complete repair of numerous bone defects. Herein, β-TCP was synthesized by wet chemical precipitation route, and their 3-D porous composites with H3BO3 and Cu nanoparticles were prepared by the solid-state reaction method with improved mechanical and biological performances. Several characterization techniques have been used to investigate the various characteristics of fabricated porous composites. SEM and TEM studies revealed the porous morphology and hexagonal sheets of the β-TCP for the composite THC8 (82TCP-10H3BO3-8Cu). Moreover, the mechanical study showed excellent compressive strength (188 MPa), a high Young's modulus (2.84 GPa), and elevated fracture toughness (9.11 MPa.m1/2). An in vitro study by MTT assay on osteoblast (MG-63) cells demonstrated no or minimal cytotoxicity at the higher concentration, 100 µg/ml after 24 h and it was found a more pronounced result at 20 µg/ml on increasing the concentration of Cu nanoparticles after incubating 72 h. The THC12 composite showed the highest antibacterial potency exclusively against B. subtilis. S. pyogene, S. typhi and E. coli. at 10 mg/ml, indicating its potential effectiveness in inhibiting all of these pathogens. Genotoxicity and cytotoxicity tests were also performed on rearing Drosophila melanogaster, and these findings did not detect any trypan blue-positive staining, which further recommended that the existence of composites did not harm the larval gut. Therefore, the fabricated porous composites THC8 and THC12 are suitable for bone regrowth without harming the surrounding cells and protect against bacterial infections.

Immunomodulatory metal-based biomaterials for cancer immunotherapy

Cancer immunotherapy, as an emerging cancer treatment approach, harnesses the patient's own immune system to effectively prevent tumor recurrence or metastasis. However, its clinical application has been significantly hindered by relatively low immune response rates. In recent years, metal-based biomaterials have been extensively studied as effective immunomodulators and potential tools for enhancing anti-tumor immune responses, enabling the reversal of immune suppression without inducing toxic side effects. This review introduces the classification of bioactive metal elements and summarizes their immune regulatory mechanisms. In addition, we discuss the immunomodulatory roles of biomaterials constructed from various metals, including aluminum, manganese, gold, calcium, zinc, iron, magnesium, and copper. More importantly, a systematic overview of their applications in enhancing immunotherapy is provided. Finally, the prospects and challenges of metal-based biomaterials with immunomodulatory functions in cancer immunotherapy are outlined.

Mg alloys with antitumor and anticorrosion properties for orthopedic oncology: A review from mechanisms to application strategies

As a primary malignant bone cancer, osteosarcoma (OS) poses a great threat to human health and is still a huge challenge for clinicians. At present, surgical resection is the main treatment strategy for OS. However, surgical intervention will result in a large bone defect, and some tumor cells remaining around the excised bone tissue often lead to the recurrence and metastasis of OS. Biomedical Mg-based materials have been widely employed as orthopedic implants in bone defect reconstruction, and, especially, they can eradicate the residual OS cells due to the antitumor activities of their degradation products. Nevertheless, the fast corrosion rate of Mg alloys has greatly limited their application scope in the biomedical field, and the improvement of the corrosion resistance will impair the antitumor effects, which mainly arise from their rapid corrosion. Hence, it is vital to balance the corrosion resistance and the antitumor activities of Mg alloys. The presented review systematically discussed the potential antitumor mechanisms of three corrosion products of Mg alloys. Moreover, several strategies to simultaneously enhance the anticorrosion properties and antitumor effects of Mg alloys were also proposed.

Vaccine adjuvants: current status, research and development, licensing, and future opportunities

Vaccines represent one of the most significant inventions in human history and have revolutionized global health. Generally, a vaccine functions by triggering the innate immune response and stimulating antigen-presenting cells, leading to a defensive adaptive immune response against a specific pathogen's antigen. As a key element, adjuvants are chemical materials often employed as additives to increase a vaccine's efficacy and immunogenicity. For over 90 years, adjuvants have been essential components in many human vaccines, improving their efficacy by enhancing, modulating, and prolonging the immune response. Here, we provide a timely and comprehensive review of the historical development and the current status of adjuvants, covering their classification, mechanisms of action, and roles in different vaccines. Additionally, we perform systematic analysis of the current licensing processes and highlights notable examples from clinical trials involving vaccine adjuvants. Looking ahead, we anticipate future trends in the field, including the development of new adjuvant formulations, the creation of innovative adjuvants, and their integration into the broader scope of systems vaccinology and vaccine delivery. The article posits that a deeper understanding of biochemistry, materials science, and vaccine immunology is crucial for advancing vaccine technology. Such advancements are expected to lead to the future development of more effective vaccines, capable of combating emerging infectious diseases and enhancing public health.

TLR7 Agonist-Loaded Gadolinium Oxide Nanotubes Promote Anti-Tumor Immunity by Activation of Innate and Adaptive Immune Responses

Improving the delivery of biomolecules to DCs and lymph nodes is critical to increasing their anti-tumor efficacy, reducing their off-target side effects, and improving their safety. In this study, Gd2O3 nanotubes with lengths of 70-80 nm, diameters of 20-30 nm, and pore sizes of up to 18 nm were synthesized using a facile one-pot solvothermal method. The Gd2O3 nanotubes showed good adsorption capacity of OVA and TLR7a, with a loading efficiency of about 100%. The Gd2O3 nanotubes showed pH-sensitive degradation and biomolecule release properties; the release of gadolinium ions, OVA, and TLR7a was slow at pH 7.4 and fast at pH 5. The Gd2O3 nanotubes showed 2.6-6.0 times higher payload retention around the injection site, 3.1 times higher cellular uptake, 1.7 times higher IL1β secretion, 1.4 times higher TNFα secretion by BMDCs, and markedly enhanced draining lymph node delivery properties. The combination of OVA, TLR7a, and Gd2O3 nanotubes significantly inhibited tumor growth and increased survival rate compared with only OVA-TLR7a, only OVA, and saline. The Gd2O3 nanotubes are biocompatible and can also be used as radiation sensitizers.

Rational design of adjuvants boosts cancer vaccines

Cancer vaccines are expected to be next breakthrough in cancer immunotherapy. In cancer vaccines, adjuvants play an important role by enhancing and reshaping tumor antigen-specific immune responses. Failures in previous cancer vaccine clinical trials can be attributed to inappropriate selection and design of tumor antigens and adjuvants. Using basic theories of tumor immunology, the development of sequencing technology and nanotechnology enables the creation of cancer vaccines through appropriate selection of tumor antigens and adjuvants and their nanoscale assembly based on the specific characteristics of each tumor. In this chapter, we begin by discussing the various types of cancer vaccines and categories of tumor antigens. Then, we summarize the classification of adjuvants for cancer vaccines, including immunostimulatory molecules and delivery systems, and clarify the various factors that influence the properties of adjuvants, such as chemical composition, structure, and surface modification. Finally, we provide perspectives and insights on rational design of adjuvants in cancer vaccines to enhance their efficacy.

Bacteria-based immunotherapy for cancer: a systematic review of preclinical studies

Immunotherapy has been emerging as a powerful strategy for cancer management. Recently, accumulating evidence has demonstrated that bacteria-based immunotherapy including naive bacteria, bacterial components, and bacterial derivatives, can modulate immune response via various cellular and molecular pathways. The key mechanisms of bacterial antitumor immunity include inducing immune cells to kill tumor cells directly or reverse the immunosuppressive microenvironment. Currently, bacterial antigens synthesized as vaccine candidates by bioengineering technology are novel antitumor immunotherapy. Especially the combination therapy of bacterial vaccine with conventional therapies may further achieve enhanced therapeutic benefits against cancers. However, the clinical translation of bacteria-based immunotherapy is limited for biosafety concerns and non-uniform production standards. In this review, we aim to summarize immunotherapy strategies based on advanced bacterial therapeutics and discuss their potential for cancer management, we will also propose approaches for optimizing bacteria-based immunotherapy for facilitating clinical translation.

Synergistic anti-tumor efficacy of a hollow mesoporous silica-based cancer vaccine and an immune checkpoint inhibitor at the local site

Immune checkpoint inhibitors elicit durable tumor regression in multiple types of tumor, but may induce potential side effects with low response rates in many tumors. Herein, to increase the therapeutic efficacy of immune checkpoint inhibitors, a hollow mesoporous silica (HMS) nanosphere-based cancer vaccine was combined with an immune checkpoint inhibitor, anti-programmed death-ligand 1 (anti-PD-L1) antibody. The HMS nanospheres function as adjuvants that promote dendritic cell activation and antigen cross-presentation. Mice immunized with the HMS-based cancer vaccine show suppressed tumor growth with increased tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-2 (IL-2) levels in their spleens compared with those without HMS-based cancer vaccine. Moreover, the HMS-based cancer vaccine synergistically acts with the anti-PD-L1 antibody on the tumor. The combination of an HMS-based cancer vaccine and an antibody markedly decreases the required dose of the immune checkpoint inhibitor. Mice locally administered with the HMS-based cancer vaccine and 1/8 dose of a standard anti-PD-L1 antibody (25 µg/mouse) show comparable anti-tumor effect and significantly increased CD4⁺ and CD8⁺ T cell populations, compared with those systemically immunized with the standard anti-PD-L1 antibody done at 200 µg/mouse. Our work presents a promising cancer treatment strategy of combining an immune checkpoint inhibitor with an HMS-based cancer vaccine. STATEMENT OF SIGNIFICANCE: The clinical benefits of checkpoint blockade therapy rekindle the hope of cancer immunotherapy. However, objective response rates in checkpoint blockade therapy remain at about 10-40% owing to multiple immunosuppressive factors. To solve these problems, herein, a hollow mesoporous silica (HMS) nanosphere-based cancer vaccine was combined with an immune checkpoint inhibitor, anti-PD-L1 antibody. The HMS-based cancer vaccine synergistically acts with the anti-PD-L1 antibody on the tumor. Mice locally administered with the HMS-based cancer vaccine and 1/8 dose of a standard anti-PD-L1 antibody (25 µg/mouse) show comparable anti-tumor effect and significantly increased CD4⁺ and CD8⁺ T cell populations, compared with those systemically immunized with the standard anti-PD-L1 antibody done at 200 µg/mouse. Our work presents a promising cancer treatment strategy of combining an immune checkpoint inhibitor with an HMS-based cancer vaccine.

Manganese-Doped Silica-Based Nanoparticles Promote the Efficacy of Antigen-Specific Immunotherapy

Prophylactic human papillomavirus (HPV) vaccines are commercially available for prevention of infection with cancerogenic HPV genotypes but are not able to combat pre-existing HPV-associated disease. In this study, we designed a nanomaterial-based therapeutic HPV vaccine, comprising manganese (Mn⁴⁺)-doped silica nanoparticles (Mn⁴⁺-SNPs) and the viral neoantigen peptide GF001 derived from the HPV16 E7 oncoprotein. We show in mice that Mn⁴⁺-SNPs act as self-adjuvants by activating the inflammatory signaling pathway via generation of reactive oxygen species, resulting in immune cell recruitment to the immunization site and dendritic cell maturation. Mn⁴⁺-SNPs further serve as Ag carriers by facilitating endo/lysosomal escape via depletion of protons in acidic endocytic compartments and subsequent Ag delivery to the cytosol for cross-presentation. The Mn⁴⁺-SNPs+GF001 nanovaccine induced strong E7-specific CD8⁺ T cell responses, leading to remission of established murine HPV16 E7-expressing solid TC-1 tumors and E7-expressing transgenic skin grafts. This vaccine construct offers a simple and general strategy for therapeutic HPV and potentially other cancer vaccines.

Tailoring inorganic nanoadjuvants towards next-generation vaccines

Vaccines, one of the most effective and powerful public health measures, have saved countless lives over the past century and still have a tremendous global impact. As an indispensable component of modern vaccines, adjuvants play a critical role in strengthening and/or shaping a specific immune response against infectious diseases as well as malignancies. The application of nanotechnology provides the possibility of precisely tailoring the building blocks of nanoadjuvants towards modern vaccines with the desired immune response. The last decade has witnessed great academic progress in inorganic nanomaterials for vaccine adjuvants in terms of nanometer-scale synthesis, structure control, and functionalization design. Inorganic adjuvants generally facilitate the delivery of antigens, allowing them to be released in a sustained manner, enhance immunogenicity, deliver antigens efficiently to specific targets, and induce a specific immune response. In particular, the recent discovery of the intrinsic immunomodulatory function of inorganic nanomaterials further allows us to shape the immune response towards the desired type and increase the efficacy of vaccines. In this article, we comprehensively review state-of-the-art research on the use of inorganic nanomaterials as vaccine adjuvants. Attention is focused on the physicochemical properties of versatile inorganic nanoadjuvants, such as composition, size, morphology, shape, hydrophobicity, and surface charge, to effectively stimulate cellular immunity, considering that the clinically used alum adjuvants can only induce strong humoral immunity. In addition, the efforts made to date to expand the application of inorganic nanoadjuvants in cancer vaccines are summarized. Finally, we discuss the future prospects and our outlook on tailoring inorganic nanoadjuvants towards next-generation vaccines.

Biodegradable Metal Ion-Doped Mesoporous Silica Nanospheres Stimulate Anticancer Th1 Immune Response in Vivo

Modern vaccines usually require accompanying adjuvants to increase the immune response to antigens. Aluminum (alum) compounds are the most commonly used adjuvants in human vaccinations for infection diseases. However, alum adjuvants are nondegradable, cause side effects due to the persistence of alum at injection sites, and are rather ineffective for cancer immunotherapy, which requires the Th1 immune response. Recently, we have shown that a plain mesoporous silica (MS) adjuvant can stimulate Th1 anticancer immunity for cancer vaccines. Herein, MS nanospheres doped with Ca, Mg, and Zn (MS-Ca, MS-Mg, and MS-Zn) showed significantly higher degradation rates than pure MS. Moreover, MS-Ca, MS-Mg, and MS-Zn nanospheres  stimulated anticancer immune response and increased the CD4⁺ and CD8⁺ T cell populations in spleen. The MS-Ca, MS-Mg, and MS-Zn nanospheres with improved biodegradability and excellent ability to induce Th1 anticancer immunity show potential for clinical applications as cancer immunoadjuvants.

Hollow ZnO Nanospheres Enhance Anticancer Immunity by Promoting CD4+ and CD8+ T Cell Populations In Vivo

Appropriate adjuvant aiding in generating robust anticancer immunity is crucial for cancer immunotherapy. Herein, hollow ZnO (HZnO) nanospheres are synthesized by a facile method using carbon nanospheres as the template. The HZnO nanospheres significantly promote the cellular uptake of a model antigen, and cytokine secretion by antigen-presenting cells in vitro. HZnO loaded with ovalbumin and polyinosinic-polycytidylic acid (poly(I:C)) inhibits cancer growth and metastasis to inguinal lymph node in a cancer cell challenge model. Moreover, HZnO loaded with autologous cancer antigens inhibits cancer cell growth in a cancer cell re-challenge model. HZnO nanospheres significantly improve the CD4⁺ and/or CD8⁺ T cell population in splenocytes of mice in both cancer cell challenge model and re-challenge model. The HZnO nanospheres can be used for cancer immunotherapy as adjuvant.

Biofunctional Ionic-Doped Calcium Phosphates: Silk Fibroin Composites for Bone Tissue Engineering Scaffolding

The treatment and regeneration of bone defects caused by traumatism or diseases have not been completely addressed by current therapies. Lately, advanced tools and technologies have been successfully developed for bone tissue regeneration. Functional scaffolding materials such as biopolymers and bioresorbable fillers have gained particular attention, owing to their ability to promote cell adhesion, proliferation, and extracellular matrix production, which promote new bone growth. Here, we present novel biofunctional scaffolds for bone regeneration composed of silk fibroin (SF) and β-tricalcium phosphate (β-TCP) and incorporating Sr, Zn, and Mn, which were successfully developed using salt-leaching followed by a freeze-drying technique. The scaffolds presented a suitable pore size, porosity, and high interconnectivity, adequate for promoting cell attachment and proliferation. The degradation behavior and compressive mechanical strengths showed that SF/ionic-doped TCP scaffolds exhibit improved characteristics for bone tissue engineering when compared with SF scaffolds alone. The in vitro bioactivity assays using a simulated body fluid showed the growth of an apatite layer. Furthermore, in vitro assays using human adipose-derived stem cells presented different effects on cell proliferation/differentiation when varying the doping agents in the biofunctional scaffolds. The incorporation of Zn into the scaffolds led to improved proliferation, while the Sr- and Mn-doped scaffolds presented higher osteogenic potential as demonstrated by DNA quantification and alkaline phosphatase activity. The combination of Sr with Zn led to an influence on cell proliferation and osteogenesis when compared with single ions. Our results indicate that biofunctional ionic-doped composite scaffolds are good candidates for further in vivo studies on bone tissue regeneration.

Hollow boron nitride nanospheres as boron reservoir for prostate cancer treatment

High global incidence of prostate cancer has led to a focus on prevention and treatment strategies to reduce the impact of this disease in public health. Boron compounds are increasingly recognized as preventative and chemotherapeutic agents. However, systemic administration of soluble boron compounds is hampered by their short half-life and low effectiveness. Here we report on hollow boron nitride (BN) spheres with controlled crystallinity and boron release that decrease cell viability and increase prostate cancer cell apoptosis. In vivo experiments on subcutaneous tumour mouse models treated with BN spheres demonstrated significant suppression of tumour growth. An orthotopic tumour growth model was also utilized and further confirmed the in vivo anti-cancer efficacy of BN spheres. Moreover, the administration of hollow BN spheres with paclitaxel leads to synergetic effects in the suppression of tumour growth. The work demonstrates that hollow BN spheres may function as a new agent for prostate cancer treatment.

Use of soluble boron compounds in prostate cancer therapy is hampered by their short half-life time and low effectiveness. Here, the authors show that boron nitride nanospheres with controlled boron release can reduce proliferation of prostate cancer cells and inhibit tumour growth in animal models.

Comprehensive Mechanism Analysis of Mesoporous-Silica-Nanoparticle-Induced Cancer Immunotherapy

A plain mesoporous silica nanoparticle without any immunomodulatory molecules significantly enhances anticancer immunity in vivo. Comprehensive mechanism of mesoporous-silica-nanoparticle-induced cancer immunotherapy is analyzed in this paper. The mesoporous silica nanoparticle promotes both Th1 and Th2 immune responses, as it accelerates lymphocytes proliferation, stimulates IFN-γ, IL-2, IL-4, and IL-10 cytokine secretion by lymphocytes ex vivo, and increases IgG, IgG1, IgG2a, IgM, and IgA antibody titers in mice serum compared with those of alum and adjuvant-free groups. Moreover, the mesoporous silica nanoparticle enhances effector memory CD4(+) and CD8(+) T cell populations in three most important immune organs (bone marrow, lymph node, and spleen) of mice compared with those of alum and adjuvant-free groups three months after adjuvant injection. The present study paves the way for the application of mesoporous silica nanoparticle as immunoadjuvant for cancer immunotherapy.

Unique antitumor property of the Mg-Ca-Sr alloys with addition of Zn

In clinical practice, tumor recurrence and metastasis after orthopedic prosthesis implantation is an intensely troublesome matter. Therefore, to develop implant materials with antitumor property is extremely necessary and meaningful. Magnesium (Mg) alloys possess superb biocompatibility, mechanical property and biodegradability in orthopedic applications. However, whether they possess antitumor property had seldom been reported. In recent years, it showed that zinc (Zn) not only promote the osteogenic activity but also exhibit good antitumor property. In our present study, Zn was selected as an alloying element for the Mg-1Ca-0.5Sr alloy to develop a multifunctional material with antitumor property. We investigated the influence of the Mg-1Ca-0.5Sr-xZn (x = 0, 2, 4, 6 wt%) alloys extracts on the proliferation rate, cell apoptosis, migration and invasion of the U2OS cell line. Our results show that Zn containing Mg alloys extracts inhibit the cell proliferation by alteration the cell cycle and inducing cell apoptosis via the activation of the mitochondria pathway. The cell migration and invasion property were also suppressed by the activation of MAPK (mitogen-activated protein kinase) pathway. Our work suggests that the Mg-1Ca-0.5Sr-6Zn alloy is expected to be a promising orthopedic implant in osteosarcoma limb-salvage surgery for avoiding tumor recurrence and metastasis.

Rod-shaped and fluorine-substituted hydroxyapatite free of molecular immunopotentiators stimulates anti-cancer immunity in vivo

Rod-shaped and fluorine-substituted hydroxyapatite nanoparticles significantly increased the cellular uptake of a model antigen by BMDCs, improved antigen presentation, stimulated immune-related cytokine secretion, and enhanced the anti-cancer immunity.