Clay Nanoparticles Elicit Long-Term Immune Responses by Forming Biodegradable Depots for Sustained Antigen Stimulation

Separable nanocomposite hydrogel microneedles for intradermal and sustained delivery of antigens to enhance adaptive immune responses

Vaccines play a critical role in combating infectious diseases and cancers, yet improving their efficacy remains challenging. Here, we introduce a separable nanocomposite hydrogel microneedle (NHMN) patch designed for intradermal and sustained delivery of ovalbumin (OVA), a model antigen, to enhance adaptive immune responses. The NHMN patch consists of an array of OVA-loaded microneedles made from photo-cross-linked methacrylated hyaluronic acid and laponite (LAP), supported by a hyaluronic acid backing. The incorporation of LAP not only enhances the mechanical strength of the pure hydrogel microneedles but also significantly prolongs OVA release. Furthermore, in vitro cell experiments demonstrate that NHMNs effectively activate dendritic cells without compromising cell viability. Upon skin penetration, NHMNs detach from the backing as the hyaluronic acid rapidly dissolves upon contact with the skin interstitial fluid, thereby acting as antigen reservoirs to release antigens to abundant skin dendritic cells. NHMNs containing 0.5% w/v LAP achieved a 15-day OVA release in vivo. Immunization studies demonstrate that the intradermal and sustained release of OVA via NHMNs elicited stronger and longer-lasting adaptive immune responses compared to conventional bolus injection. Given its easy to use, painless and minimally invasive features, the NHMN patch shows promise in improving vaccination accessibility and efficacy against a range of diseases. STATEMENT OF SIGNIFICANCE: The study introduces a separable nanocomposite hydrogel microneedle (NHMN) patch. This patch consists of an array of ovalbumin (OVA, a model antigen)-loaded microneedles made from photo-cross-linked methacrylated hyaluronic acid and laponite, with a hyaluronic acid backing, designed for intradermal and sustained delivery of antigens. This patch addresses several key challenges in traditional vaccination methods, including poor antigen uptake and presentation, and rapid systematic clearance. The incorporation of laponite enhances mechanical strength of microneedles, promotes dendritic cell activation, and significantly slows down antigen release. NHMN-based vaccination elicits stronger and longer-lasting adaptive immune responses compared to conventional bolus injection. This NHMN patch holds great potential for improving the efficacy, accessibility, and patient comfort of vaccinations against a range of diseases.

A laponite-based immunologically active gel delivery system for long-acting tumor vaccine

Traditional bolus vaccines typically require multiple doses, which complicates the vaccination process and may cause missed shots, leading to sub-optimal immunity and reduced vaccine effectiveness. Herein, a gel-based long-acting vaccine system with self-adjuvant properties based on laponite was constructed to simplify vaccination procedures and improve vaccine effectiveness. Firstly, the gel system could recruit multiple types of immune cells to form immune niches. Secondly, it could achieve sustained delivery of antigens to lymph nodes by active transport and passive drainage. Then, the gel system triggered the formation of a large number of germinal centers, which elicited enhanced and durable humoral immune responses, as well as strong cellular immune responses. As a result, it eventually showed good prophylactic and therapeutic effects in a variety of tumor models including melanoma, colorectal cancer and peritoneal metastasis models. By further combining the immunoadjuvant CpG ODN and cytokine IL-12, the effect of the gel-vaccine could be further enhanced. In a murine peritoneal metastasis model of colorectal carcinoma, a single administration of the gel-vaccine resulted in complete tumor eradication in 8/9 mice. In summary, this study developed an immunologically active gel-vaccine system. And as a robust and versatile vaccine platform, by loading different antigens and adjuvants, this gel-vaccine system is expected to realize its better therapeutic potential.

Layered Double Hydroxides (LDH) as Delivery Vehicles of a Chimeric Protein Carrying Epitopes from the Porcine Reproductive and Respiratory Syndrome Virus

The Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) causes reproductive failure and respiratory symptoms, leading to huge economic losses for the pig farming industry. Although several vaccines against PRRSV are available in the market; they show an overall low efficacy, and several countries have the need for vaccines covering the local, circulating variants. This project aims at developing a new chimeric antigen targeting specific epitopes from PRRSV and evaluating two test adjuvants to formulate a vaccine candidate. The test antigen was called LTB-PRRSV, which was produced recombinantly in Escherichia coli and consisted of the heat labile enterotoxin B subunit from E. coli (LTB) and four epitopes from PRRSV. LTB-PRRSV was rescued as inclusion bodies and methods for its solubilization, IMAC-based purification, and refolding were standardized, leading to mean yields of 18 mg of pure protein per liter culture. Layered double hydroxides (LDH) have been used as vaccine adjuvants given their biocompatibility, low cost, and positive surface charge that allows an efficient adsorption of negatively charged biomolecules. Therefore, LDH were selected as delivery vehicles of LTB-PRRSV. Pure LTB-PRRSV was adsorbed onto LDH by incubation at different LDH:LTB-PRRSV mass ratios (1:0.25, 1:0.5, 1:1, and 1:2) and at pH 9.5. The best adsorption occurred with a 1:2 mass ratio, and in a sucrose-tween solution. The conjugates obtained had a polydispersity index of 0.26, a hydrodynamic diameter of 192 nm, and a final antigen concentration of 64.2 μg/mL. An immunogenicity assessment was performed by injecting mice with LDH:LTB-PRRSV, Alum/LTB-PRRSV, or LTB-PRRSV in a scheme comprising three immunizations at two-week intervals and two dose levels (1 and 5 μg). LTB-PRRSV was capable of inducing strong humoral responses, which lasted for a longer period when LDH was used as the delivery vehicle/adjuvant. The potential of LDH to serve as an attractive carrier for veterinary vaccines is discussed.

Intranasal delivery of phenytoin loaded layered double hydroxide nanoparticles improves therapeutic effect on epileptic seizures

Improving the efficiency of antiseizure medication entering the brain is the key to reducing its peripheral toxicity. A combination of intranasal administration and nanomedicine presents a practical approach for treating epileptic seizures via bypassing the blood-brain barrier. In this study, phenytoin (PHT) loaded layered double hydroxide nanoparticles (BSA-LDHs-PHT) were fabricated via a coprecipitation - hydrothermal method for epileptic seizure control. In this study, we expound on the preparation method and characterization of BSA-LDHs-PHT. In-vitro drug release experiment shows both rapid and continuous drug release from BSA-LDHs-PHT, which is crucial for acute seizure control and chronic epilepsy therapy. In-vivo biodistribution assays after intranasal administration indicate excellent brain targeting ability of BSA-LDHs. Compared to BSA-Cyanine5.5, BSA-LDHs-Cyanine5.5 were associated with a higher brain/peripheral ratio across all tested time points. Following intranasal delivery with small doses of BSA-LDHs-PHT, the latency of seizures in the pentylenetetrazole-induced mouse models was effectively improved. Collectively, the present study successfully designed and applied BSA-LDHs-PHT as a promising strategy for treating epileptic seizures with an enhanced therapeutic effect.

Silicon-containing nanomedicine and biomaterials: materials chemistry, multi-dimensional design, and biomedical application

The invention of silica-based bioactive glass in the late 1960s has sparked significant interest in exploring a wide range of silicon-containing biomaterials from the macroscale to the nanoscale. Over the past few decades, these biomaterials have been extensively explored for their potential in diverse biomedical applications, considering their remarkable bioactivity, excellent biocompatibility, facile surface functionalization, controllable synthesis, etc. However, to expedite the clinical translation and the unexpected utilization of silicon-composed nanomedicine and biomaterials, it is highly desirable to achieve a thorough comprehension of their characteristics and biological effects from an overall perspective. In this review, we provide a comprehensive discussion on the state-of-the-art progress of silicon-composed biomaterials, including their classification, characteristics, fabrication methods, and versatile biomedical applications. Additionally, we highlight the multi-dimensional design of both pure and hybrid silicon-composed nanomedicine and biomaterials and their intrinsic biological effects and interactions with biological systems. Their extensive biomedical applications span from drug delivery and bioimaging to therapeutic interventions and regenerative medicine, showcasing the significance of their rational design and fabrication to meet specific requirements and optimize their theranostic performance. Additionally, we offer insights into the future prospects and potential challenges regarding silicon-composed nanomedicine and biomaterials. By shedding light on these exciting research advances, we aspire to foster further progress in the biomedical field and drive the development of innovative silicon-composed nanomedicine and biomaterials with transformative applications in biomedicine.

Enhancing Cancer Chemo-Immunotherapy: Innovative Approaches for Overcoming Immunosuppression by Functional Nanomaterials

Chemotherapy is a critical modality in cancer therapy to combat malignant cell proliferation by directly attacking cancer cells and inducing immunogenic cell death, serving as a vital component of multi-modal treatment strategies for enhanced therapeutic outcomes. However, chemotherapy may inadvertently contribute to the immunosuppression of the tumor microenvironment (TME), inducing the suppression of antitumor immune responses, which can ultimately affect therapeutic efficacy. Chemo-immunotherapy, combining chemotherapy and immunotherapy in cancer treatment, has emerged as a ground-breaking approach to target and eliminate malignant tumors and revolutionize the treatment landscape, offering promising, durable responses for various malignancies. Notably, functional nanomaterials have substantially contributed to chemo-immunotherapy by co-delivering chemo-immunotherapeutic agents and modulating TME. In this review, recent advancements in chemo-immunotherapy are thus summarized to enhance treatment effectiveness, achieved by reversing the immunosuppressive TME (ITME) through the exploitation of immunotherapeutic drugs, or immunoregulatory nanomaterials. The effects of two-way immunomodulation and the causes of immunoaugmentation and suppression during chemotherapy are illustrated. The current strategies of chemo-immunotherapy to surmount the ITME and the functional materials to target and regulate the ITME are discussed and compared. The perspective on tumor immunosuppression reversal strategy is finally proposed.

Nanovaccines for Advancing Long-Lasting Immunity against Infectious Diseases

Infectious diseases, particularly life-threatening pathogens such as small pox and influenza, have substantial implications on public health and global economies. Vaccination is a key approach to combat existing and emerging pathogens. Immunological memory is an essential characteristic used to evaluate vaccine efficacy and durability and the basis for the long-term effects of vaccines in protecting against future infections; however, optimizing the potency, improving the quality, and enhancing the durability of immune responses remains challenging and a focus for research involving investigation of nanovaccine technologies. In this review, we describe how nanovaccines can address the challenges for conventional vaccines in stimulating adaptive immune memory responses to protect against reinfection. We discuss protein and nonprotein nanoparticles as useful antigen platforms, including those with highly ordered and repetitive antigen array presentation to enhance immunogenicity through cross-linking with multiple B cell receptors, and with a focus on antigen properties. In addition, we describe how nanoadjuvants can improve immune responses by providing enhanced access to lymph nodes, lymphnode targeting, germinal center retention, and long-lasting immune response generation. Nanotechnology has the advantage to facilitate vaccine induction of long-lasting immunity against infectious diseases, now and in the future.

A Booster for Radiofrequency Ablation: Advanced Adjuvant Therapy via In Situ Nanovaccine Synergized with Anti-programmed Death Ligand 1 Immunotherapy for Systemically Constraining Hepatocellular Carcinoma

Radiofrequency ablation (RFA) is one of the most common minimally invasive techniques for treating hepatocellular carcinoma (HCC), which could destroy tumors through hyperthermia and generate massive tumor-associated antigens (TAAs). However, residual malignant tissues or small satellite lesions are hard to eliminate, generally resulting in metastases and recurrence. Herein, an advanced in situ nanovaccine formed by layered double hydroxides carrying cGAMP (STING agonist) (LDHs-cGAMP) and adsorbed TAAs was designed to potentiate the RFA-induced antitumor immune response. As-prepared LDHs-cGAMP could effectively enter cancerous or immune cells, inducing a stronger type I interferon (IFN-I) response. After further adsorption of TAAs, nanovaccine generated sustained immune stimulation and efficiently promoted activation of dendritic cells (DCs). Notably, infiltrations of cytotoxic lymphocytes (CTLs) and activated DCs in tumor and lymph nodes were significantly enhanced after nanovaccine treatment, which distinctly inhibited primary, distant, and metastasis of liver cancer. Furthermore, such a nanovaccine strategy greatly changed the tumor immune microenvironment and promoted the response efficiency of anti-programmed death ligand 1 (αPD-L1) immunotherapy, significantly arresting the poorly immunogenic hepa1-6 liver cancer progression. These findings demonstrate the potential of nanovaccine as a booster for RFA in liver cancer therapy and provide a promising in situ cancer vaccination strategy.

Assessing the Adjuvant Effect of Layered Double Hydroxides (LDH) on BALB/c Mice

The discovery and validation of new adjuvants are critical areas for vaccinology. Mineral materials (e.g., alum microparticles) have been used for a long time as adjuvants in human vaccine formulations. Nonetheless, the use of nanosized materials is a promising approach to diversify the properties of adjuvants. Nanoclays are potential adjuvants proposed by some research groups. However, their adjuvant mechanisms and safety have not been fully elucidated. Herein, we aimed at expanding the knowledge on the potential adjuvanticity of layered double hydroxide (LDH) nanoparticles by reporting a detailed method for the synthesis and characterization of LDHs and the adsorption of a model antigen (bovine serum albumin, BSA). LDHs varying in diameter (from 56 to 88 nm) were obtained, and an in vitro evaluation revealed that the LDHs are not inherently toxic. BSA was passively adsorbed onto the LDHs, and the immunogenicity in mice of the conjugates obtained was compared to that of free BSA and BSA co-administered with alum (Alum-BSA). The LDH-BSA conjugates induced a higher humoral response that lasted for a longer period compared with that of free BSA and Alum-BSA, confirming that LDH exerts adjuvant effects. The 56 nm LDH particles were deemed as the more efficient carrier since they induced a higher and more balanced Th1/Th2 response than the 88 nm particles. This study is a contribution toward expanding the characterization and use of nanoclays in vaccinology and justifies further studies with pathogen-specific antigens.

Nanoparticle-Based Adjuvants and Delivery Systems for Modern Vaccines

Ever since the development of the first vaccine, vaccination has had the great impact on global health, leading to the decrease in the burden of numerous infectious diseases. However, there is a constant need to improve existing vaccines and develop new vaccination strategies and vaccine platforms that induce a broader immune response compared to traditional vaccines. Modern vaccines tend to rely on certain nanotechnology platforms but are still expected to be readily available and easy for large-scale manufacturing and to induce a durable immune response. In this review, we present an overview of the most promising nanoadjuvants and nanoparticulate delivery systems and discuss their benefits from tehchnological and immunological standpoints as well as their objective drawbacks and possible side effects. The presented nano alums, silica and clay nanoparticles, nanoemulsions, adenoviral-vectored systems, adeno-associated viral vectors, vesicular stomatitis viral vectors, lentiviral vectors, virus-like particles (including bacteriophage-based ones) and virosomes indicate that vaccine developers can now choose different adjuvants and/or delivery systems as per the requirement, specific to combatting different infectious diseases.

"Trojan horse" nanoparticle-delivered cancer cell membrane vaccines to enhance cancer immunotherapy by overcoming immune-escape

Cancer cell membranes (CCMs) have emerged as advanced cancer treatment vaccines to boost the immune response against cancer and have shown great potential in cancer immunotherapy. However, the CCM vaccine confronts the challenges of a weak and short immune response, ascribed to the immune escape and low accumulation of the CCM in antigen presentation cells (APCs). To overcome these shortcomings, we devised a "Trojan horse" CCM nano-vaccine delivered by layered double hydroxide (LDH) nanoparticles with mannose targeting and bovine serum albumin (BSA) coating to overcome the immune escape challenge, efficiently boosting the immune response to cancer cells. This "Trojan horse" CCM nano-vaccine, named LGCMB, is constructed by assembling the CCM antigen on CpG-LDH (LG), followed by mannose-BSA coating for the APC target and BSA coating to mask immune-escape protein on the CCM. The in vitro cellular uptake and maturation data have clearly shown that the BSA coating strategy with mannose as a "Trojan horse" efficiently targeted APCs (macrophages and DCs) and effectively inhibited the immune escape of the CCM, competently stimulating the APC maturation. Moreover, LGCMB can migrate to the draining lymph nodes (LNs) and trigger tumor-specific CD8⁺ T cell responses in vivo. As expected, the LGCMB nano-vaccine significantly suppressed tumor growth in vivo, showing great potential as a precision cancer vaccine.

Engineered NanoAlum from aluminum turns cold tumor hot for potentiating cancer metalloimmunotherapy

The poor cancer immunotherapy outcome has been closely related to immunosuppressive tumor microenvironment (TME), which usually inactivates the antitumor immune cells and leads to immune tolerance. Metalloimmunotherapy by supplementing nutritional metal ions into TME has emerged as a potential strategy to activate the tumor-resident immune cells. Herein, we engineered a magnesium-contained nano-aluminum adjuvant (NanoAlum) through hydrolyzing a mixture of Mg(OH)₂ and Al(OH)₃, which has highly similar components to commercial Imject Alum. Peritumoral injection of NanoAlum effectively neutralized the acidic TME while releasing Mg²⁺ to activate the tumor-resident T cells. Meanwhile, NanoAlum also blocked the autophagy pathway in tumor cells and subsequently induced cell apoptosis. The in vivo studies showed that merely peritumoral injection of NanoAlum successfully inhibited the growth of solid tumors in mice. On this basis, NanoAlum combined with chemical drug methotrexate or immunomodulatory adjuvant CpG further induced potent antigen-specific antitumor immunity. Overall, our study first provides a rational design for engineering tumor-targeted nanomodulator from clinical adjuvants to achieve effective cancer metalloimmunotherapy against solid tumors.

Nanovaccines: Merits, and diverse roles in boosting antitumor immune responses

An attractive type of cancer immunotherapy is cancer therapeutic vaccines that induce antitumor immunity effectively. Although supportive results in the recent vaccine studies, there are still numerous drawbacks, such as poor stability, weak immunogenicity and strong toxicity, to be tackled for promoting the potency and durability of antitumor efficacy. NPs (Nanoparticles)-based vaccines offer unique opportunities to breakthrough the current bottleneck. As a rule, nanovaccines are new the generations of vaccines that use NPs as carriers and/or adjuvants. Several advantages of nanovaccines are constantly explored, including optimal nanometer size, high stability, plenty of antigen loading, enhanced immunogenicity, tunable antigen presentation, more retention in lymph nodes and promote patient compliance by a lower frequency of dosing. Here, we summarized the merits and highlight the diverse role nanovaccines play in improving antitumor responses.

Clay nanoparticles efficiently deliver small interfering RNA to intact plant leaf cells

RNA interference is triggered in plants by the exogenous application of double-stranded RNA or small interfering RNA (siRNA) to silence the expression of target genes. This approach can potentially provide insights into metabolic pathways and gene function and afford plant protection against viruses and other plant pathogens. However, the effective delivery of biomolecules such as siRNA into plant cells is difficult because of the unique barrier imposed by the plant cell wall. Here, we demonstrate that 40-nm layered double hydroxide (LDH) nanoparticles are rapidly taken up by intact Nicotiana benthamiana leaf cells and by chloroplasts, following their application via infiltration. We also describe the distribution of infiltrated LDH nanoparticles in leaves and demonstrate their translocation through the apoplast and vasculature system. Furthermore, we show that 40-nm LDH nanoparticles can greatly enhance the internalization of nucleic acids by N. benthamiana leaf cells to facilitate siRNA-mediated downregulation of targeted transgene mRNA by >70% within 1 day of exogenous application. Together, our results show that 40-nm LDH nanoparticle is an effective platform for delivery of siRNA into intact plant leaf cells.

Development of Foot-and-Mouth Disease Vaccines in Recent Years

Foot-and-mouth disease (FMD) is a serious disease affecting the global graziery industry. Once an epidemic occurs, it can lead to economic and trade stagnation. In recent decades, FMD has been effectively controlled and even successfully eradicated in some countries or regions through mandatory vaccination with inactivated foot-and-mouth disease vaccines. Nevertheless, FMD still occurs in some parts of Africa and Asia. The transmission efficiency of foot-and-mouth disease is high. Both disease countries and disease-free countries should always be prepared to deal with outbreaks of FMD. The development of vaccines has played a key role in this regard. This paper summarizes the development of several promising vaccines including progress and design ideas. It also provides ways to develop a new generation of vaccines for FMDV and other major diseases.

A Peritumorally Injected Immunomodulating Adjuvant Elicits Robust and Safe Metalloimmunotherapy against Solid Tumors

Clinical immunotherapy of solid tumors elicits durable responses only in a minority of patients, largely due to the highly immunosuppressive tumor microenvironment (TME). Although rational combinations of vaccine adjuvants with inflammatory cytokines or immune agonists that relieve immunosuppression represent an appealing therapeutic strategy against solid tumors, there are unavoidable nonspecific toxicities due to the pleiotropy of cytokines and undesired activation of off-target cells. Herein, a Zn²⁺ doped layered double hydroxide (Zn-LDH) based immunomodulating adjuvant, which not only relieves immunosuppression but also elicits robust antitumor immunity, is reported. Peritumorally injected Zn-LDH sustainably neutralizes acidic TME and releases abundant Zn²⁺ , promoting a pro-inflammatory network composed of M1-tumor-associated macrophages, cytotoxic T cells, and natural-killer cells. Moreover, the Zn-LDH internalized by tumor cells effectively disrupts endo-/lysosomes to block autophagy and induces mitochondrial damage, and the released Zn²⁺ activates the cGas-STING signaling pathway to induce immunogenic cell death, which further promotes the release of tumor-associated antigens to induce antigen-specific cytotoxic T lymphocytes. Unprecedentedly, merely injection of Zn-LDH adjuvant, without using any cytotoxic inflammatory cytokines or immune agonists, significantly inhibits the growth, recurrence, and metastasis of solid tumors in mice. This study provides a rational bottom-up design of potent adjuvant for cancer metalloimmunotherapy against solid tumors.

Nanoclays: Promising Materials for Vaccinology

Clay materials and nanoclays have gained recent popularity in the vaccinology field, with biocompatibility, simple functionalization, low toxicity, and low-cost as their main attributes. As elements of nanovaccines, halloysite nanotubes (natural), layered double hydroxides and hectorite (synthetic) are the nanoclays that have advanced into the vaccinology field. Until now, only physisorption has been used to modify the surface of nanoclays with antigens, adjuvants, and/or ligands to create nanovaccines. Protocols to covalently attach these molecules have not been developed with nanoclays, only procedures to develop adsorbents based on nanoclays that could be extended to develop nanovaccine conjugates. In this review, we describe the approaches evaluated on different nanovaccine candidates reported in articles, the immunological results obtained with them and the most advanced approaches in the preclinical field, while describing the nanomaterial itself. In addition, complex systems that use nanoclays were included and described. The safety of nanoclays as carriers is an important key fact to determine their true potential as nanovaccine candidates in humans. Here, we present the evaluations reported in this field. Finally, we point out the perspectives in the development of vaccine prototypes using nanoclays as antigen carriers.

Efficient Immunotherapy of Drug-Free Layered Double Hydroxide Nanoparticles via Neutralizing Excess Acid and Blocking Tumor Cell Autophagy

Cancer immunotherapy efficacy is largely limited by the suppressive tumor immune microenvironment (TIME) where antitumor immune cells are inhibited and tumor antigens continue to mutate or be lost. To remodel the TIME, we here applied weakly alkaline layered double hydroxide nanoparticles (LDH NPs) to neutralize the excess acid and block autophagy of tumor cells for neoadjuvant cancer immunotherapy. Peritumoral injection of LDH NPs provided a long-term and efficient acid-neutralization in the TIME, blocked the lysosome-mediated autophagy pathway in tumor cells, and increased the levels of antitumor tumor-associated macrophages and T cells. These LDH NPs captured tumor antigens released in the tumor tissues and effectively inhibited the growth of both melanoma and colon tumors in vivo. These findings indicate that LDH NPs, as an immunomodulator and adjuvant, successfully "awaken" and promote the host innate and adaptive immune systems, showing promising potential for solid tumor immunotherapy.

Layered double hydroxide-based nanomaterials for biomedical applications

Against the backdrop of increased public health awareness, inorganic nanomaterials have been widely explored as promising nanoagents for various kinds of biomedical applications. Layered double hydroxides (LDHs), with versatile physicochemical advantages including excellent biocompatibility, pH-sensitive biodegradability, highly tunable chemical composition and structure, and ease of composite formation with other materials, have shown great promise in biomedical applications. In this review, we comprehensively summarize the recent advances in LDH-based nanomaterials for biomedical applications. Firstly, the material categories and advantages of LDH-based nanomaterials are discussed. The preparation and surface modification of LDH-based nanomaterials, including pristine LDHs, LDH-based nanocomposites and LDH-derived nanomaterials, are then described. Thereafter, we systematically describe the great potential of LDHs in biomedical applications including drug/gene delivery, bioimaging diagnosis, cancer therapy, biosensing, tissue engineering, and anti-bacteria. Finally, on the basis of the current state of the art, we conclude with insights on the remaining challenges and future prospects in this rapidly emerging field.

Topology dependent modification of layered double hydroxide for therapeutic and diagnostic platform

Layered double hydroxide is a family of two-dimensional materials with wide range of compositions. Recently, its ability to accommodate various chemical species and biocompatibility have been attracted in the biomedical applications to develop drug delivery system and nanodiagnostics. In this review, we categorized biomedical approaches of layered double hydroxide with respect to the three topologies of, namely, interlayer space, outer surface with particle edge, and the lattice points. There have been extensive researches on the intercalation of drug or tracing to make use of interlayer space of layered double hydroxide for drug stabilization, sustained release, cellular delivery and etc. Outer surface or edge has been utilized to immobilization of large therapeutic moieties and to attach tracing moiety. Lattice points consisting of various metal species could be utilized for the specific metal species like paramagnetic elements or radioisotopes. Based on these topologies in layered double hydroxide, both the synthetic routes and the achieved functionalities in terms of biomedical application will be discussed.

Interference of layered double hydroxide nanoparticles with pathways for biomedical applications

Recent decades have witnessed a surge of explorations into the application of multifarious materials, especially biomedical applications. Among them, layered double hydroxides (LDHs) have been widely developed as typical inorganic layer materials to achieve remarkable advancements. Multiple physicochemical properties endow LDHs with excellent merits in biomedical applications. Moreover, LDH nanoplatforms could serve as "molecular switches", which are capable of the controlled release of payloads under specific physiological pH conditions but are stable during circulation in the bloodstream. In addition, LDHs themselves are composed of several specific cations and possess favorable biological effects or regulatory roles in various cellular functions. These advantages have caused LDHs to become increasingly of interest in the area of nanomedicine. Recent efforts have been devoted to revealing the potential factors that interfere with the biological pathways of LDH-based nanoparticles, such as their applications in shaping the functions of immune cells and in determining the fate of stem cells and tumor treatments, which are comprehensively described herein. In addition, several intracellular signaling pathways interfering with by LDHs in the above applications were also systematically expatiated. Finally, the future development and challenges of LDH-based nanomedicine are discussed in the context of the ultimate goal of practical clinical application.

Application Perspectives of Nanomedicine in Cancer Treatment

Cancer is a disease that seriously threatens human health. Based on the improvement of traditional treatment methods and the development of new treatment modes, the pattern of cancer treatment is constantly being optimized. Nanomedicine plays an important role in these evolving tumor treatment modalities. In this article, we outline the applications of nanomedicine in three important tumor-related fields: chemotherapy, gene therapy, and immunotherapy. According to the current common problems, such as poor targeting of first-line chemotherapy drugs, easy destruction of nucleic acid drugs, and common immune-related adverse events in immunotherapy, we discuss how nanomedicine can be combined with these treatment modalities, provide typical examples, and summarize the advantages brought by the application of nanomedicine.

Mg/Al-LDH as a nano-adjuvant for pertussis vaccine: a evaluation compared with aluminum hydroxide adjuvant

Background. Layered double hydroxide (LDH) has been demonstrated as a highly efficient antigen platform to induce effective and durable immune response. However, whether LDH nanoparticles could act as an adjuvant for pertussis vaccines is still unknown. Here we evaluated the potential of Mg/Al-LDH as a nano-adjuvant to improve immune response against pertussis and compared it with commercial aluminum hydroxide (AH) adjuvant.Method. The Mg/Al-LDH nanoparticles were synthesized by a hydrothermal reaction. The morphology, structure and size of Mg/Al-LDH were characterized by transmission electron microscope, x-ray diffraction and MALVERN particle analysis. The ovalbumin and Pertussis toxin (PTd) was adsorbed to Mg/Al-LDH. The immune response of antigen-LDH complex was evaluated in mice, compared with commercial adjuvant alum. Hematoxylin-eosin staining was used to evaluate the inflammatory response at injection site.Results. The synthetic Mg/Al-LDH nanoparticles showed a typical hexagonal lamellar structure. The average size of synthetic nanoparticles was 102.9 nm with PDI of 0.13 and zeta potential was 44.4 mV. Mg/Al-LDH nanoparticles effectively adsorbed protein antigen and mediated antigen uptake by DC cells. Animal experiments showed that Mg/Al-LDH gave enhancement in anti-pertussis toxin (PTd) humoral immune response, which was considerable to commercial AH adjuvant. Finally, Mg/Al-LDH produced a slighter inflammatory response than AH at injection site and this injury was quickly recovered.Conclusion. Our study demonstrated the potential of Mg/Al-LDH as an effective adjuvant for pertussis vaccine, which induced comparable antibody response and had a better safety compared with commercial AH adjuvant.

LDH nanoparticle adjuvant subunit vaccine induces an effective immune response for porcine epidemic diarrhea virus

Porcine Epidemic Diarrhea (PED) is a highly contagious intestinal disease which mostly caused by Porcine Epidemic Diarrhea Virus (PEDV). The PED has caused huge economic losses to the pig industry all over the world and a valid PEDV vaccine is needed to prevent the infection. In this study, we constructed expression plasmid based on the spike (S) gene of the epidemic PEDV strain. The recombinant eukaryotic S (Se) and prokaryotic S (Sp) subunit proteins were expressed and purified as vaccine antigens. We designed a new subunit vaccine based on S proteins, adjuvanted with layered double hydroxide (LDH). The results indicated that the LDH adjuvanted subunit vaccines induced a better immune effect in terms of antibody level and cellular immune response. In conclusion, this study showed a new design of a PEDV subunit vaccine with nanotechnology and demonstrated the potential for its clinical application.

Delivery of nanovaccine towards lymphoid organs: recent strategies in enhancing cancer immunotherapy

With the in-depth exploration on cancer therapeutic nanovaccines, increasing evidence shows that the poor delivery of nanovaccines to lymphoid organs has become the culprit limiting the rapid induction of anti-tumor immune response. Unlike the conventional prophylactic vaccines that mainly form a depot at the injection site to gradually trigger durable immune response, the rapid proliferation of tumors requires an efficient delivery of nanovaccines to lymphoid organs for rapid induction of anti-tumor immunity. Optimization of the physicochemical properties of nanovaccine (e.g., size, shape, charge, colloidal stability and surface ligands) is an effective strategy to enhance their accumulation in lymphoid organs, and nanovaccines with dynamic structures are also designed for precise targeted delivery of lymphoid organs or their subregions. The recent progress of these nanovaccine delivery strategies is highlighted in this review, and the challenges and future direction are also discussed.

Sheet-like clay nanoparticles deliver RNA into developing pollen to efficiently silence a target gene

Topical application of double-stranded RNA (dsRNA) can induce RNA interference (RNAi) and modify traits in plants without genetic modification. However, delivering dsRNA into plant cells remains challenging. Using developing tomato (Solanum lycopersicum) pollen as a model plant cell system, we demonstrate that layered double hydroxide (LDH) nanoparticles up to 50 nm in diameter are readily internalized, particularly by early bicellular pollen, in both energy-dependent and energy-independent manners and without physical or chemical aids. More importantly, these LDH nanoparticles efficiently deliver dsRNA into tomato pollen within 2-4 h of incubation, resulting in an 89% decrease in transgene reporter mRNA levels in early bicellular pollen 3-d post-treatment, compared with a 37% decrease induced by the same dose of naked dsRNA. The target gene silencing is dependent on the LDH particle size, the dsRNA dose, the LDH-dsRNA complexing ratio, and the treatment time. Our findings indicate that LDH nanoparticles are an effective nonviral vector for the effective delivery of dsRNA and other biomolecules into plant cells.

Two-dimensional layered double hydroxide nanoadjuvant: recent progress and future direction

Layered double hydroxide (LDH) is a 'sandwich'-like two-dimensional clay material that has been systematically investigated for biomedical application in the past two decades. LDH is an alum-similar adjuvant, which has a well-defined layered crystal structure and exhibits high adjuvanticity. The unique structure of LDH includes positively charged layers composed of divalent and trivalent cations and anion-exchangeable interlayer galleries. Among the many variants of LDH, MgAl-LDH (the cationic ions are Mg2+ and Al3+) has the highest affinity to antigens, bioadjuvants and drug molecules, and exhibits superior biosafety. Past research studies indicate that MgAl-LDH can simultaneously load antigens, bioadjuvants and molecular drugs to amplify the strength of immune responses, and induce broad-spectrum immune responses. Moreover, the size and dispersity of MgAl-LDH in biological environments can be well controlled to actively deliver antigens to the immune system, realizing the rapid induction and maintenance of durable immune responses. Furthermore, the functionalization of MgAl-LDH nanoadjuvants enables it to capture antigens in situ and induce personalized immune responses, thereby more effectively overcoming complex diseases. In this review, we comprehensively summarize the development and application of MgAl-LDH nanoparticles as a vaccine adjuvant, demonstrating that MgAl-LDH is the most potential adjuvant for clinical application.

Layered double hydroxide nanoparticles as an adjuvant for inactivated foot-and-mouth disease vaccine in pigs

Background

Foot-and-mouth disease (FMD) is a highly transmissible disease that leads to vast economic losses in many countries. Prevention using inactivated vaccines is one effective measure used to control FMD. Unfortunately, inactivated FMD vaccines provide only short-term protection and require a cold-chain system. In recent years, many studies have shown that layered double metal hydroxides (LDHs) carrying antigens can be used to strongly induce immune responses. In this study, LDH nanoparticles (NPs) were prepared by hydrothermal synthesis. LDH particle size, electric potential, and morphology were measured and observed. The adsorption capacity of LDH NPs to FMDV was tested. The effects of LDH as an adjuvant on inactivated FMDV vaccines were further evaluated and compared with commercial FMDV Montanide ISA-206 in BALB/C female mice and Yorkshire pigs.

Results

LDH NPs were successfully prepared with a uniform particle size of ~ 87.21 nm, regular edges, a loose hexagonal shape and positive zeta charge of 32 mV. The maximum absorption concentration was 0.16–0.31 μg FMDV/μg LDH. In the mouse experiment, antibody levels in group LDH + FMDV were significantly higher compared to group saline + FMDV (P < 0.01) from days 42–98 and were significantly higher to group ISA-206 + FMDV on day 56 post-immunization (P < 0.05). After day 14 post-immunization, IFN-γ content was significantly increased (P < 0.05). In the pig experiment, antibody levels in both the ISA-206 + FMDV and LDH + FMDV were positive and were significantly higher compared with the PBS group on day 7 (P < 0.005). Antibody levels in 90% pigs were positive on day 56 in the LDH group. The neutralizing antibody levels in the LDH and ISA-206 groups were significantly higher from days 7–28 compared to the PBS control group (P < 0.05). Thus, LDH NPs were effective at inducing an immune response against FMDV.

Conclusions

LDHs with a loose hexagonal shape and a positive charge were prepared and evaluated as adjuvant for FMD vaccine. It was demonstrated that LDHs can induce immune responses in mice and pigs. In addition, the LDHs produced antibodies continuously which may indicate a slow-release effect. The study shows that LDHs may act as a potentially useful FMDV adjuvant.

Chemical Strategies to Boost Cancer Vaccines

Personalized cancer vaccines (PCVs) are reinvigorating vaccine strategies in cancer immunotherapy. In contrast to adoptive T-cell therapy and checkpoint blockade, the PCV strategy modulates the innate and adaptive immune systems with broader activation to redeploy antitumor immunity with individualized tumor-specific antigens (neoantigens). Following a sequential scheme of tumor biopsy, mutation analysis, and epitope prediction, the administration of neoantigens with synthetic long peptide (SLP) or mRNA formulations dramatically improves the population and activity of antigen-specific CD4+ and CD8+ T cells. Despite the promising prospect of PCVs, there is still great potential for optimizing prevaccination procedures and vaccine potency. In particular, the arduous development of tumor-associated antigen (TAA)-based vaccines provides valuable experience and rational principles for augmenting vaccine potency which is expected to advance PCV through the design of adjuvants, delivery systems, and immunosuppressive tumor microenvironment (TME) reversion since current personalized vaccination simply admixes antigens with adjuvants. Considering the broader application of TAA-based vaccine design, these two strategies complement each other and can lead to both personalized and universal therapeutic methods. Chemical strategies provide vast opportunities for (1) exploring novel adjuvants, including synthetic molecules and materials with optimizable activity, (2) constructing efficient and precise delivery systems to avoid systemic diffusion, improve biosafety, target secondary lymphoid organs, and enhance antigen presentation, and (3) combining bioengineering methods to innovate improvements in conventional vaccination, "smartly" re-educate the TME, and modulate antitumor immunity. As chemical strategies have proven versatility, reliability, and universality in the design of T cell- and B cell-based antitumor vaccines, the union of such numerous chemical methods in vaccine construction is expected to provide new vigor and vitality in cancer treatment.

Cancer Nanomedicines in an Evolving Oncology Landscape

Nanomedicine represents an important class of cancer therapy. Clinical translation of cancer nanomedicine has significantly reduced the toxicity and adverse consequences of standard-of-care chemotherapy. Recent advances in new cancer treatment modalities (e.g., gene and immune therapies) are profoundly changing the oncology landscape, bringing with them new requirements and challenges for next-generation cancer nanomedicines. We present an overview of cancer nanomedicines in four emerging oncology-associated fields: (i) gene therapy, (ii) immunotherapy, (iii) extracellular vesicle (EV) therapy, and (iv) machine learning-assisted therapy. We discuss the incorporation of nanomedicine into these emerging disciplines, present prominent examples, and evaluate their advantages and challenges. Finally, we discuss future opportunities for next-generation cancer nanomedicines.

Reactive Oxygen Species (ROS)-Responsive Nanomedicine for Solving Ischemia-Reperfusion Injury

Ischemia-reperfusion injury (IRI) is a severe condition for most organs, which could occur in various tissues including brain, heart, liver, and kidney, etc. As one of the major hazards, reactive oxygen species (ROS) is excessively generated after IRI, which causes severe damage inside tissues and further induces the following injury via inflammatory response. However, current medical strategies could not thoroughly diagnose and prevent this disease, eventually leading to severe sequelae by missing the best time point for therapy. In the past decade, various nanoparticles that could selectively respond to ROS have been developed and applied in IRI. These advanced nanomedicines have shown efficient performance in detecting and treating a series of IRI (e.g., acute kidney injury, acute liver injury, and ischemic stroke, etc.), which are well-summarized in the current review. In addition, the nano-platforms (e.g., anti-IL-6 antibody, rapamycin, and hydrogen sulfide delivering nanoparticles, etc.) for preventing IRI during organ transplantation have also been included. Moreover, the development and challenges of ROS-responsive nanomedicine are systematically discussed for guiding the future direction.

A biomimetic yeast shell vaccine coated with layered double hydroxides induces a robust humoral and cellular immune response against tumors

Enhancing both the humoral and cellular immune response for tumor vaccination remains a challenge. Inspired by natural pathogen structures, we took β-glucan particles derived from a baker's yeast cell shell (YS) as a vaccine carrier and danger signal for dendritic cells (DCs), and coated the YS with catanionic layered double hydroxides (LDH) by electrostatic adsorption to form a biomimetic yeast cell particle (YSL). Our experimental results showed that the YSL vaccine efficiently targeted antigen-presenting cells (APCs) and remarkably enhanced antigen cross-presentation, and strongly improved the activation and maturation of DCs. Moreover, the YSL vaccine elicited an extremely high antibody titer and strong antigen-specific cytotoxic T lymphocyte together with mixed Th1/Th17 cellular immune responses and induced marked prophylactic and therapeutic effects against E.G7-OVA tumors in mouse models. These results suggest that YSL, integrating a yeast shell to mimic natural pathogens and LDH with high antigen-loading capacity and lysosome escape, is a promising tumor vaccine platform for rapid, effective and strong induction of both humoral and cellular immune responses.

A self-aggregating peptide: implications for the development of thermostable vaccine candidates

BACKGROUND

The use of biomaterials has been expanded to improve the characteristics of vaccines. Recently we have identified that the peptide PH_(1-110) from polyhedrin self-aggregates and incorporates foreign proteins to form particles. We have proposed that this peptide can be used as an antigen carrying system for vaccines. However, the immune response generated by the antigen fused to the peptide has not been fully characterized. In addition, the adjuvant effect and thermostability of the particles has not been evaluated.

RESULTS

In the present study we demonstrate the use of a system developed to generate nano and microparticles carrying as a fusion protein peptides or proteins of interest to be used as vaccines. These particles are purified easily by centrifugation. Immunization of animals with the particles in the absence of adjuvant result in a robust and long-lasting immune response. Proteins contained inside the particles are maintained for over 1 year at ambient temperature, preserving their immunological properties.

CONCLUSION

The rapid and efficient production of the particles in addition to the robust immune response they generate position this system as an excellent method for the rapid response against emerging diseases. The thermostability conferred by the particle system facilitates the distribution of the vaccines in developing countries or areas with no electricity.

Layered double hydroxide eliminate embryotoxicity of chemotherapeutic drug through BMP-SMAD signaling pathway

Recent studies indicate that exogenous chemotherapy agents can cross the placenta barrier and cause fetal toxicity, while there exists barely alternative therapy for pregnant cancer patients. Here, we show a robust protective effect of layered double hydroxide (LDH) against etoposide (VP16) induced in vitro mouse embryonic stem cells (mESCs) toxicity and in vivo embryo developmental disorders. The nano-composite system (L-V) abrogated the original VP16 generated mitochondrial mediated mESCs toxicity totally, surprisingly maintained the pluripotency without leukemia inhibitory factor (LIF) and prevented the down-regulation of ectoderm marker expression during spontaneous embryoid bodies differentiation. Fetal growth retardation, the related placenta and skeletal structural abnormalities and long-term toxicity in the offspring were generated when pregnant mice exposed to VP16, while these detrimental effects were abolished when substituted with L-V. The different uterine drug accumulation of VP16 and L-V contributed to partly cause for the functional variation. And further transcriptome analysis confirmed developmental related BMP4-SMAD6 signaling pathway is of crucial importance. Our study revealed the devastating effects of VP16 on embryonic development and the toxicity-relieve method using nano-carrier system, which will provide important guidance for clinical application of LDH as alternative therapeutic system with minimal side effects for pregnant women diagnosed with cancer.

The application of nanotechnology in enhancing immunotherapy for cancer treatment: current effects and perspective

Cancer immunotherapy is emerging as a promising treatment modality that suppresses and eliminates tumors by re-activating and maintaining the tumor-immune cycle, and further enhancing the body's anti-tumor immune response. Despite the impressive therapeutic potential of immunotherapy approaches such as immune checkpoint inhibitors and tumor vaccines in pre-clinical and clinical applications, the effective response is limited by insufficient accumulation in tumor tissues and severe side-effects. Recent years have witnessed the rise of nanotechnology as a solution to improve these technical weaknesses due to its inherent biophysical properties and multifunctional modifying potential. In this review, we summarized and discussed the current status of nanoparticle-enhanced cancer immunotherapy strategies, including intensified delivery of tumor vaccines and immune adjuvants, immune checkpoint inhibitor vehicles, targeting capacity to tumor-draining lymph nodes and immune cells, triggered releasing and regulating specific tumor microenvironments, and adoptive cell therapy enhancement effects.

Nanoparticle-Based Nanomedicines to Promote Cancer Immunotherapy: Recent Advances and Future Directions

Cancer immunotherapy is a promising cancer terminator by directing the patient's own immune system in the fight against this challenging disorder. Despite the monumental therapeutic potential of several immunotherapy strategies in clinical applications, the efficacious responses of a wide range of immunotherapeutic agents are limited in virtue of their inadequate accumulation in the tumor tissue and fatal side effects. In the last decades, increasing evidences disclose that nanotechnology acts as an appealing solution to address these technical barriers via conferring rational physicochemical properties to nanomaterials. In this Review, an imperative emphasis will be drawn from the current understanding of the effect of a nanosystem's structure characteristics (e.g., size, shape, surface charge, elasticity) and its chemical modification on its transport and biodistribution behavior. Subsequently, rapid-moving advances of nanoparticle-based cancer immunotherapies are summarized from traditional vaccine strategies to recent novel approaches, including delivery of immunotherapeutics (such as whole cancer cell vaccines, immune checkpoint blockade, and immunogenic cell death) and engineered immune cells, to regulate tumor microenvironment and activate cellular immunity. The future prospects may involve in the rational combination of a few immunotherapies for more efficient cancer inhibition and elimination.

Degradability and Clearance of Inorganic Nanoparticles for Biomedical Applications

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

The Pathways for Layered Double Hydroxide Nanoparticles to Enhance Antigen (Cross)-Presentation on Immune Cells as Adjuvants for Protein Vaccines

Nanoparticles (NPs) are intensively investigated as adjuvants in new generation vaccines, while how these NPs promote the immune responses has not been well understood. In this research, we have tried to elucidate the possible pathways for layered double hydroxide (LDH) NPs to provoke immune responses. As previously reported, LDH NPs efficiently deliver antigens to antigen presenting cells (APCs). In this research, we have found that these internalized LDH NPs are not released by these APCs within 8 h. We have for the first time found that macrophage cells exchange the internalized LDH NPs with other surrounding ones, which may promote immune responses in an additional way. Moreover, the internalized LDH-antigen NPs significantly facilitate the maturation of immature DCs and enhance cross-presentation of epitope/MHC class I complexes on the DC surface. This research would help understand the NP adjuvant mechanism and further assist the design of new specific NPs as more efficient nano-adjuvants.