Fever-Inspired Immunotherapy Based on Photothermal CpG Nanotherapeutics: The Critical Role of Mild Heat in Regulating Tumor Microenvironment

Emerging nanoparticle platforms for CpG oligonucleotide delivery

Unmethylated cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs), which were therapeutic DNA with high immunostimulatory activity, have been applied in widespread applications from basic research to clinics as therapeutic agents for cancer immunotherapy, viral infection, allergic diseases and asthma since their discovery in 1995. The major factors to consider for clinical translation using CpG motifs are the protection of CpG ODNs from DNase degradation and the delivery of CpG ODNs to the Toll-like receptor-9 expressed human B-cells and plasmacytoid dendritic cells. Therefore, great efforts have been devoted to the advances of efficient delivery systems for CpG ODNs. In this review, we outline new horizons and recent developments in this field, providing a comprehensive summary of the nanoparticle-based CpG delivery systems developed to improve the efficacy of CpG-mediated immune responses, including DNA nanostructures, inorganic nanoparticles, polymer nanoparticles, metal-organic-frameworks, lipid-based nanosystems, proteins and peptides, as well as exosomes and cell membrane nanoparticles. Moreover, future challenges in the establishment of CpG delivery systems for immunotherapeutic applications are discussed. We expect that the continuously growing interest in the development of CpG-based immunotherapy will certainly fuel the excitement and stimulation in medicine research.

Pulsed Photothermal Therapy of Solid Tumors as a Precondition for Immunotherapy

Photothermal therapy (PTT) refers to the use of plasmonic nanoparticles to convert electromagnetic radiation in the near infrared region to heat and kill tumor cells. Continuous wave lasers have been used clinically to induce PTT, but the treatment is associated with heat-induced tissue damage that limits usability. Here, the engineering and validation of a novel long-pulsed laser device able to induce selective and localized mild hyperthermia in tumors while reducing the heat affected zone and unwanted damage to surrounding tissue are reported. Long-pulsed PTT induces acute necrotic cell death in heat affected areas and the release of tumor associated antigens. This antigen release triggers maturation and stimulation of CD80/CD86 in dendritic cells in vivo that primes a cytotoxic T cell response. Accordingly, long-pulsed PTT enhances the therapeutic effects of immune checkpoint inhibition and increases survival of mice with bladder cancer. Combined, the data promote long-pulsed PTT as a safe and effective strategy for enhancing therapeutic responses to immune checkpoint inhibitors while minimizing unwanted tissue damage.

Immunomodulatory Prodrug Micelles Imitate Mild Heat Effects to Reshape Tumor Microenvironment for Enhanced Cancer Immunotherapy

Physical stimulation with mild heat possesses the notable ability to induce immunomodulation within the tumor microenvironment (TME). It transforms the immunosuppressive TME into an immune-active state, making tumors more receptive to immune checkpoint inhibitor (ICI) therapy. Transient receptor potential vanilloid 1 (TRPV1), which can be activated by mild heat, holds the potential to induce these alterations in the TME. However, achieving precise temperature control within tumors while protecting neighboring tissues remains a significant challenge when using external heat sources. Taking inspiration from the heat sensation elicited by capsaicin-containing products activating TRPV1, this study employs capsaicin to chemically stimulate TRPV1, imitating immunomodulatory benefits akin to those induced by mild heat. This involves developing a glutathione (GSH)-responsive immunomodulatory prodrug micelle system to deliver capsaicin and an ICI (BMS202) concurrently. Following intravenous administration, the prodrug micelles accumulate at the tumor site through the enhanced permeability and retention effect. Within the GSH-rich TME, the micelles disintegrate and release capsaicin and BMS202. The released capsaicin activates TRPV1 expressed in the TME, enhancing programmed death ligand 1 expression on tumor cell surfaces and promoting T cell recruitment into the TME, rendering it more immunologically active. Meanwhile, the liberated BMS202 blocks immune checkpoints on tumor cells and T cells, activating the recruited T cells and ultimately eradicating the tumors. This innovative strategy represents a comprehensive approach to fine-tune the TME, significantly amplifying the effectiveness of cancer immunotherapy by exploiting the TRPV1 pathway and enabling in situ control of immunomodulation within the TME.

In Situ Nanofiber Patch Boosts Postoperative Hepatocellular Carcinoma Immune Activation by Trimodal Combination Therapy

Poor clinical efficacy associated with postoperative hepatocellular carcinoma (HCC) often results from recurrence and metastasis. Hence, research has focused on establishing an effective multimodal therapy. However, complex combinations of active ingredients require multiple functions in therapeutic systems. Herein, a portable nanofiber patch composing germanium phosphorus (GeP) and anlotinib (AL) was designed to form a versatile platform for molecularly targeted photothermal-immune checkpoint blockade (ICB) trimodal combination therapy. The patches possess hydrophilic, satisfactory mechanical, and excellent photothermal conversion properties. Moreover, they achieve a penetrating and sustained drug release. The near-infrared light-assisted GeP-induced temperature increase regulates AL release, downregulating the expression of vascular-related factor receptors, triggering immunogenic cell death of tumor cells, and inducing dendritic cell maturation. Simultaneously, ICB therapy (programmed cell death ligand 1, PD-L1) was introduced to improve treatment outcomes. Notably, this trimodal combination therapy significantly inhibits vascular hypergrowth, enhances effector T-cell infiltration, and sensitizes the PD-L1 antibody response, boosting immunotherapy to suppress residual HCC recurrence and metastasis. Further validation of the genome sequencing results revealed cell pathways related primarily to regulatory immune effects. This study demonstrates the use of an effective and practical nanofiber patch to improve multimodal therapy of postoperative HCC, with high clinical translation value.

Multimodal Imaging-Guided Photoimmunotherapy of Pancreatic Cancer by Organosilica Nanomedicine

Immune checkpoint blockade (ICB) treatments have contributed to substantial clinical progress. However, challenges persist, including inefficient drug delivery and penetration into deep tumor areas, inadequate response to ICB treatments, and potential risk of inflammation due to over-activation of immune cells and uncontrolled release of cytokines following immunotherapy. In response, this study, for the first time, presents a multimodal imaging-guided organosilica nanomedicine (DCCGP) for photoimmunotherapy of pancreatic cancer. The novel DCCGP nanoplatform integrates fluorescence, magnetic resonance, and real-time infrared photothermal imaging, thereby enhancing diagnostic precision and treatment efficacy for pancreatic cancer. In addition, the incorporated copper sulfide nanoparticles (CuS NPs) lead to improved tumor penetration and provide external regulation of immunotherapy via photothermal stimulation. The synergistic immunotherapy effect is realized through the photothermal behavior of CuS NPs, inducing immunogenic cell death and relieving the immunosuppressive tumor microenvironment. Coupling photothermal stimulation with αPD-L1-induced ICB, the platform amplifies the clearance efficiency of tumor cells, achieving an optimized synergistic photoimmunotherapy effect. This study offers a promising strategy for the clinical application of ICB-based combined immunotherapy and presents valuable insights for applications of organosilica in precise tumor immunotherapy and theranostics.

PD-L1 blockade TAM-dependently potentiates mild photothermal therapy against triple-negative breast cancer

The present work was an endeavor to shed light on how mild photothermia possibly synergizes with immune checkpoint inhibition for tumor therapy. We established mild photothermal heating protocols to generate temperatures of 43 °C and 45 °C in both in vitro and in vivo mouse 4T1 triple-negative breast cancer (TNBC) models using polyglycerol-coated carbon nanohorns (CNH-PG) and 808 nm laser irradiation. Next, we found that 1) CNH-PG-mediated mild photothermia (CNH-PG-mPT) significantly increased expression of the immune checkpoint PD-L1 and type-1 macrophage (M1) markers in the TNBC tumors; 2) CNH-PG-mPT had a lower level of anti-tumor efficacy which was markedly potentiated by BMS-1, a PD-L1 blocker. These observations prompted us to explore the synergetic mechanisms of CNH-PG-mPT and BMS-1 in the context of tumor cell-macrophage interactions mediated by PD-L1 since tumor-associated macrophages (TAMs) are a major source of PD-L1 expression in tumors. In vitro, the study then identified two dimensions where BMS-1 potentiated CNH-PG-mPT. First, CNH-PG-mPT induced PD-L1 upregulation in the tumor cells and showed a low level of cytotoxicity which was potentiated by BMS-1. Second, CNH-PG-mPT skewed TAMs towards an M1-like anti-tumor phenotype with upregulated PD-L1, and BMS-1 bolstered the M1-like phenotype. The synergistic effects of BMS-1 and CNH-PG-mPT both on the tumor cells and TAMs were more pronounced when the two cell populations were in co-culture. Further in vivo study confirmed PD-L1 upregulation both in tumor cells and TAMs in the TNBC tumors following treatment of CNH-PG-mPT. Significantly, TAMs depletion largely abolished the anti-TNBC efficacy of CNH-PG-mPT alone and in synergy with BMS-1. Collectively, our findings reveal PD-L1 upregulation to be a key response of TNBC to mild photothermal stress, which plays a pro-survival role in the tumor cells while also acting as a brake on the M1-like activation of the TAMs. Blockade of mPT‑induced PD‑L1 achieves synergistic anti-TNBC efficacy by taking the intrinsic survival edge off the tumor cells on one hand and taking the brakes off the M1-like TAMs on the other. Our findings reveal a novel way (i.e. mild thermia plus PD-L1 blockade) to modulate the TAMs-tumor cell interaction to instigate a mutiny of the TAMs against their host tumor cells.

Dendritic cell hybrid nanovaccine for mild heat inspired cancer immunotherapy

Cancer therapeutic vaccine can induce antigen-specific immune response, which has shown great potential in cancer immunotherapy. As the key factor of vaccine, antigen plays a central role in eliciting antitumor immunity. However, the insufficient antigen delivery and low efficiency of antigen presentation by dendritic cells (DCs) have greatly restricted the therapeutic efficiency of vaccine. Here we developed a kind of DC hybrid zinc phosphate nanoparticles to co-deliver antigenic peptide and photosensitive melanin. Owing to the chelating ability of Zn2+, the nanoparticles can co-encapsulate antigenic peptide and melanin with high efficiency. The nanovaccine showed good physiological stability with the hydration particle size was approximately 30 nm, and zeta potential was around - 10 mV. The nanovaccine showed homologous targeting effect to DCs in vivo and in vitro, efficiently delivering antigen to DCs. Meanwhile, the nanovaccine could effectively reflux to the tumor-draining lymph nodes. When combined with near-infrared irradiation, the nanovaccine induced effective mild heat in vitro and in vivo to promote antigen presentation. After administrating to MC38 tumor-bearing mice, the hybrid nanovaccine effectively promoted the maturation of DCs, the expansion of cytotoxic T lymphocytes and helper T cells, and the secretion of immunostimulatory cytokines, thereby significantly inhibiting tumor growth.

Immunotherapeutic effect of photothermal-mediated exosomes secreted from breast cancer cells

Aim: Exosomal damage-associated molecular patterns can play a key role in immunostimulation and changing the cold tumor microenvironment to hot. Materials & methods: This study examined the immunostimulation effect of photothermal and hyperthermia-treated 4T1 cell-derived exosomes on 4T1 cell-induced breast tumors in BALB/c animal models. Exosomes were characterized for HSP70, HSP90 and HMGB-1 before injection into mice and tumor tissues were analyzed for IL-6, IL-12 and IL-1β, CD4 and CD8 T-cell permeability, and PD-L1 expression. Results: Thermal treatments increased high damage-associated molecular patterns containing exosome secretion and the permeability of T cells to tumors, leading to tumor growth inhibition. Conclusion: Photothermal-derived exosomes showed higher damage-associated molecular patterns than hyperthermia with a higher immunostimulation and inhibiting tumor growth effect.

Automated Approach to In Vitro Image-Guided Photothermal Therapy with Top-Down and Bottom-Up-Synthesized Graphene Quantum Dots

Graphene-based materials have been the subject of interest for photothermal therapy due to their high light-to-heat conversion efficiency. Based on recent studies, graphene quantum dots (GQDs) are expected to possess advantageous photothermal properties and facilitate fluorescence image-tracking in the visible and near-infrared (NIR), while surpassing other graphene-based materials in their biocompatibility. Several GQD structures including reduced graphene quantum dots (RGQDs) derived from reduced graphene oxide via top-down oxidation and hyaluronic acid graphene quantum dots (HGQDs) hydrothermally bottom-up synthesized from molecular hyaluronic acid were employed to test these capabilities in the present work. These GQDs possess substantial NIR absorption and fluorescence throughout the visible and NIR beneficial for in vivo imaging while being biocompatible at up to 1.7 mg/mL concentrations. In aqueous suspensions, RGQDs and HGQDs irradiated with a low power (0.9 W/cm2) 808 nm NIR laser facilitate a temperature increase up to 47.0 °C, which is sufficient for cancer tumor ablation. In vitro photothermal experiments sampling multiple conditions directly in the 96-well plate were performed using an automated simultaneous irradiation/measurement system developed on the basis of a 3D printer. In this study, HGQDs and RGQDs facilitated the heating of HeLa cancer cells up to 54.5 °C, leading to the drastic inhibition of cell viability from over 80% down to 22.9%. GQD's fluorescence in the visible and NIR traces their successful internalization into HeLa cells maximized at 20 h suggesting both extracellular and intracellular photothermal treatment capabilities. The combination of the photothermal and imaging modalities tested in vitro makes the GQDs developed in this work prospective agents for cancer theragnostics.

Application of nanomaterials in combined thermal ablation and immunotherapy for liver tumors

Thermal ablation is one of the important treatments for liver tumors, but the postoperative recurrence rate is high. Thermal ablation has been reported to trigger the release of tumor-associated antigens, which in turn initiates antitumor immune response. However, this anti-tumor immune effect cannot effectively suppress tumor recurrence due to the obstacles of antigen presentation, the formation of tumor-suppressive immune microenvironment, and the hypoxic and hypovascular tumor microenvironment. Therefore, using immunotherapy to enhance the antitumor immune effect after thermal ablation is a potential strategy to improve the prognosis of tumor patients. However, free immune drugs have the disadvantages of poor targeting and short half-life. Nanomaterials have the advantages of strong modifiability, controllable drug ratio, and excellent targeting. Based on the characteristics of the tumor immune microenvironment after thermal ablation, scholars have designed nano-immunopharmaceuticals that can increase the tumor permeability of immune drugs, stimulate antigen presentation, and reshape the tumor immune microenvironment. This review focuses on the role of nanomaterials in tumor ablation combined with immunotherapy for liver tumors.

Ultra-thin layered double hydroxide-mediated photothermal therapy combine with asynchronous blockade of PD-L1 and NR2F6 inhibit hepatocellular carcinoma

Background

The efficacy of immune checkpoint blockade (ICB), in the treatment of hepatocellular carcinoma (HCC), is limited due to low levels of tumor-infiltrating T lymphocytes and deficient checkpoint blockade in this immunologically "cool" tumor. Thus, combination approaches are needed to increase the response rates of ICB and induce synergistic antitumor immunity.

Methods

Herein, we designed a pH-sensitive multifunctional nanoplatform based on layered double hydroxides (LDHs) loaded with siRNA to block the intracellular immune checkpoint NR2F6, together with the asynchronous blockade surface receptor PD-L1 to induce strong synergistic antitumor immunity. Moreover, photothermal therapy (PTT) generated by LDHs after laser irradiation modified an immunologically “cold” microenvironment to potentiate Nr2f6-siRNA and anti-PD-L1 immunotherapy. Flow cytometry was performed to assess the immune responses initiated by the multifunctional nanoplatform.

Results

Under the slightly acidic tumor extracellular environment, PEG detached and the re-exposed positively charged LDHs enhanced tumor accumulation and cell uptake. The accumulated siRNA suppressed the signal of dual protumor activity in both immune and H22 tumor cells by silencing the NR2F6 gene, which further reduced the tumor burden and enhanced systemic antitumor immunity. The responses include enhanced tumor infiltration by CD4⁺ helper T cells, CD8⁺ cytotoxic T cells, and mature dendritic cells; the significantly decreased level of immune suppressed regulator T cells. The therapeutic responses were also attributed to the production of IL-2, IFN-γ, and TNF-α. The prepared nanoparticles also exhibited potential magnetic resonance imaging (MRI) ability, which could serve to guide synergistic immunotherapy treatment.

Conclusions

In summary, the three combinations of PTT, NR2F6 gene ablation and anti-PD-L1 can promote a synergistic immune response to inhibit the progression of primary HCC tumors and prevent metastasis. This study can be considered a proof-of-concept for the targeting of surface and intracellular immune checkpoints to supplement the existing HCC immunotherapy treatments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01565-9.

An update on dual targeting strategy for cancer treatment

The key issue in the treatment of solid tumors is the lack of efficient strategies for the targeted delivery and accumulation of therapeutic cargoes in the tumor microenvironment (TME). Targeting approaches are designed for more efficient delivery of therapeutic agents to cancer cells while minimizing drug toxicity to normal cells and off-targeting effects, while maximizing the eradication of cancer cells. The highly complicated interrelationship between the physicochemical properties of nanoparticles, and the physiological and pathological barriers that are required to cross, dictates the need for the success of targeting strategies. Dual targeting is an approach that uses both purely biological strategies and physicochemical responsive smart delivery strategies to increase the accumulation of nanoparticles within the TME and improve targeting efficiency towards cancer cells. In both approaches, either one single ligand is used for targeting a single receptor on different cells, or two different ligands for targeting two different receptors on the same or different cells. Smart delivery strategies are able to respond to triggers that are typical of specific disease sites, such as pH, certain specific enzymes, or redox conditions. These strategies are expected to lead to more precise targeting and better accumulation of nano-therapeutics. This review describes the classification and principles of dual targeting approaches and critically reviews the efficiency of dual targeting strategies, and the rationale behind the choice of ligands. We focus on new approaches for smart drug delivery in which synthetic and/or biological moieties are attached to nanoparticles by TME-specific responsive linkers and advanced camouflaged nanoparticles.

Bacteria-based nanodrug for anticancer therapy

Bacteria-based immunotherapy has become a promising strategy to induce innate and adaptive responses for fighting cancer. The advantages of bacteriolytic tumor therapy mainly lie in stimulation of innate immunity and colonization of some bacteria targeting the tumor microenvironment (TME). These bacteria have cytotoxic proteins and immune modulating factors that can effectively restrain tumor growth. However, cancer is a multifactorial disease and single therapy is typically unable to eradicate tumors. Rapid progress has been made in combining bacteria with nanotechnology. Using the nanomolecular properties of bacterial products for tumor treatment preserves many features from the original bacteria while providing some unique advantages. Nano-bacterial therapy can enhance permeability and retention of drugs, increase the tolerability of the targeted drugs, promote the release of immune cell mediators, and induce immunogenic cell death pathways. In addition, combining nano-bacterial mediated antitumor therapeutic systems with modern therapy is an effective strategy for overcoming existing barriers in antitumor treatment and can achieve satisfactory therapeutic efficacy. Overall, exploring the immune antitumor characteristics of adjuvant clinical treatment with bacteria can provide potential efficacious treatment strategies for combatting cancer.

Multifunctional theranostic nanoparticles for multi-modal imaging-guided CAR-T immunotherapy and chemo-photothermal combinational therapy of non-Hodgkin's lymphoma

Accurate and effective tumor diagnosis, detection, and treatment are key for improving the survival rates of patients. Chimeric antigen receptor T (CAR-T) cell therapy has shown remarkable clinical success in eradicating hematologic malignancies. However, the hostile microenvironment in solid tumors severely prevents CAR-T cells from migrating and from infiltrating and killing malignant cells. Tumor microenvironment modulation strategies have attracted much attention in the field of cancer immunotherapy. Multifunctional nanoplatforms that integrate the advantages of different therapeutic techniques can allow for the multimodal synergistic treatment of tumors. In this study, a biocompatible, tumor-targeting, on-demand approach combining CAR-T cell immunotherapy and a chemo-photothermal therapy nanoplatform (FA-Gd-GERTs@Ibrutinib) based on gadolinium-loaded gap-enhanced Raman tags (Gd-GERTs) has been developed for multimodal imaging, and it provides a reliable treatment strategy for solid tumor immunotherapy via microenvironment reconstruction. In our study, folate (FA) receptor targeted molecules are used to improve the accuracy and sensitivity of computed tomography/magnetic resonance/Raman multimodal tumor imaging. The photothermal effect of the nanoprobe can promote the angiogenesis of lymphoma tissue, destroy the extracellular matrix, loosen compact tissue, stimulate chemokine secretion, and effectively enhance the infiltration ability in the case of non-Hodgkin's lymphoma, without dampening the CD19 CAR-T cell activity. The treatment results in tumor-bearing mice proved the existence of excellent synergistic therapy; photothermal therapy improves the accumulation and effector function of CAR-T cells within solid tumors. It is believed that multifunctional nanomaterials with targeted multi-modal imaging capabilities that support combination therapy can provide an efficient route for accurate diagnosis and efficient treatment.

Cell-Selective Encapsulation within Metal-Organic Framework Shells via Precursor-Functionalized Aptamer Identification for Whole-Cell Cancer Vaccine

Single-cell encapsulation is an emerging technology to endow cells with various functions, of which developing new applications in vivo is in high demand. Currently, metal-organic frameworks (MOFs) that are used as nanometric shells to coat living cells, however, have not realized cell-selective encapsulation. Here, a biocompatible and selective cell encapsulation strategy based on precursor-functionalized nucleolin aptamer and in situ MOF mineralization on the aptamer-identified cancer cell surface are developed. After MOF coating, the encapsulated cancer cells undergo immunogenic cell death, which is found associated with the changed cell stiffness (indicated by Young's modulus). The immunogenic dead cancer cells are used as whole-cell cancer vaccines (WCCVs), forming the integral WCCV-in-shell structure with enhanced immunogenicity ascribing from the surface-exposed calreticulin to promote dendritic cell recruitment, antigen presentation, and T-cell activation. The major activation pathways in the immune response are identified including tumor necrosis factor signaling pathway, cytokine-cytokine receptor interaction, and Toll-like receptor signaling pathway, suggesting the potential adjuvant effect of the MOF shells. After vaccination, WCCV-in-shell shows much better tumor immunoprophylaxis than either the imperfectly coated cancer cells or the traditional WCCV. This strategy is promising for the universal and facile development of novel whole-cell vaccines.

Spatiotemporally Controllable Distribution of Combination Therapeutics in Solid Tumors by Dually Modified Bacteria

Methods capable of distributing antitumor therapeutics uniformly and durably throughout an entire tumor would be of great significance in maximizing their treatment efficacy, but they have proven to be extremely challenging. Here, bacteria-mediated spatiotemporally controllable distribution of combination therapeutics in solid tumors is reported to reprogram the immune microenvironment for optimizing antitumor efficacy. By combining synthetic biology and interfacial chemistry, bacteria are inside and outside concurrently modified to express photothermal melanin and to attach immune checkpoint inhibitors on their surface. Due to the nature of bacteria to colonize the hypoxia intratumoral environment, both therapeutic agents can be distributed homogenously and lastingly in tumors during ex vivo human and in vivo mouse studies. Spatiotemporally controllable localization of melanin can repeatedly generate a moderate yet uniform heating of the tumor upon light exposure in a broad treatment window. Combination with similarly localized inhibitors elicits a dual photothermally stimulated and checkpoint-blockade-mediated immune activation effect, synergistically reprogramming the immunosuppressive tumor microenvironment. Therapeutic values are demonstrated by significantly inhibited tumor growth and prolonged survival of mice in both subcutaneous and orthotopic murine models. Colonization of dually modified bacteria paves an avenue for spatiotemporally controllable distribution of therapeutic drugs in solid tumors.

Amino acid sequence determines the adjuvant potency of a D-Tetra-Peptide hydrogel

The development of novel vaccine adjuvants is essential for the production of modern vaccines against infectious agents and cancer. We recently reported a supramolecular hydrogel of a self-assembling D-tetra-peptide named...

Nanomedicine potentiates mild photothermal therapy for tumor ablation

The booming photothermal therapy (PTT) has achieved great progress in non-invasive oncotherapy, and paves a novel way for clinical oncotherapy. Of note, mild temperature PTT (mPTT) of 42–45 °C could avoid treatment bottleneck of the traditional PTT, including nonspecific injury to normal tissues, vasculature and host antitumor immunity. However, cancer cells can resist mPTT via heat shock response and autophagy, thus leading to insufficient mPTT monotherapy to ablate tumor. To overcome the deficient antitumor efficacy caused by thermo-resistance of cancer cells and mono mPTT, synergistic therapies towards cancer cells have been conducted with mPTT. This review summarizes the recent advances in nanomedicine-potentiated mPTT for cancer treatment, including strategies for enhanced single-mode mPTT and mPTT plus synergistic therapies. Moreover, challenges and prospects for clinical translation of nanomedicine-potentiated mPTT are discussed.

Cancer Cytomembrane-Cloaked Prussian Blue Nanoparticles Enhance the Efficacy of Mild-Temperature Photothermal Therapy by Disrupting Mitochondrial Functions of Cancer Cells

Despite its success against cancer, photothermal therapy (PTT) (>50 °C) suffers from several limitations such as triggering inflammation and facilitating immune escape and metastasis and also damage to the surrounding normal cells. Mild-temperature PTT has been proposed to override these shortcomings. We developed a nanosystem using HepG2 cancer cell membrane-cloaked zinc glutamate-modified Prussian blue nanoparticles with triphenylphosphine-conjugated lonidamine (HmPGTL NPs). This innovative approach achieved an efficient mild-temperature PTT effect by downregulating the production of intracellular ATP. This disrupts a section of heat shock proteins that cushion cancer cells against heat. The physicochemical properties, anti-tumor efficacy, and mechanisms of HmPGTL NPs both in vitro and in vivo were investigated. Moreover, the nanoparticles cloaked with the HepG2 cell membrane substantially prolonged the circulation time in vivo. Overall, the designed nanocomposites enhance the efficacy of mild-temperature PTT by disrupting the production of ATP in cancer cells. Thus, we anticipate that the mild-temperature PTT nanosystem will certainly present its enormous potential in various biomedical applications.

Photothermal therapy combined with neoantigen cancer vaccination for effective immunotherapy against large established tumors and distant metastasis

Photothermal therapy (PTT) and neoantigen cancer vaccine each offers minimally invasive and highly specific cancer therapy; however, they are not effective against large established tumors due to physical and biological barriers that attenuate thermal ablation and abolish anti-tumor immunity. Here, we designed and performed comparative study using small (~ 50 mm3) and large (> 100 mm3) tumors to examine how tumor size affects the therapeutic efficiency of PTT and neoantigen cancer vaccine. We show that spiky gold nanoparticle (SGNP)-based PTT and synergistic dual adjuvant-based neoantigen cancer vaccine can efficiently regress small tumors as a single agent, but not large tumors due to limited internal heating and immunosuppressive tumor microenvironment (TME). We report that PTT sensitizes tumors to neoantigen cancer vaccination by destroying and compromising the TME via thermally induced cellular and molecular damage, while neoantigen cancer vaccine reverts local immune suppression induced by PTT and shapes residual TME in favor of anti-tumor immunity. The combination therapy efficiently eradicated large local tumors and also exerted strong abscopal effect against pre-established distant tumors with robust systemic anti-tumor immunity. Thus, PTT combined with neoantigen cancer vaccine is a promising nano-immunotherapy for personalized therapy of advanced cancer.

Recent advances in nanoparticles mediated photothermal therapy induced tumor regression

Photothermal therapy (PTT) is a minimally invasive procedure for treating cancer. The two significant prerequisites of PTT are the photothermal therapeutic agent (PTA) and near-infrared radiation (NIR). The PTA absorbs NIR, causing hyperthermia in the malignant cells. This increased temperature at the tumor microenvironment finally results in tumor cell damage. Nanoparticles play a crucial role in PTT, aiding in the passive and active targeting of the PTA to the tumor microenvironment. Through enhanced permeation and retention effect and surface-engineering, specific targeting could be achieved. This novel delivery tool provides the advantages of changing the shape, size, and surface attributes of the carriers containing PTAs, which might facilitate tumor regression significantly. Further, inclusion of surface engineering of nanoparticles is facilitated through ligating ligands specific to overexpressed receptors on the cancer cell surface. Thus, transforming nanoparticles grants the ability to combine different treatment strategies with PTT to enhance cancer treatment. This review emphasizes properties of PTAs, conjugated biomolecules of PTAs, and the combinatorial techniques for a better therapeutic effect of PTT using the nanoparticle platform.

Tumor immunotherapy and multi-mode therapies mediated by medical imaging of nanoprobes

Immunotherapy is an effective tumor treatment strategy that has several advantages over conventional methods such as surgery, radiotherapy and chemotherapy. Studies show that multifunctional nanoprobes can achieve multi-mode image-guided multiple tumor treatment modes. The tumor cells killed by chemotherapies or phototherapies release antigens that trigger an immune response and augment the effects of tumor immunotherapy. Thus, combining immunotherapy and multifunctional nanoprobes can achieve early cancer diagnosis and treatment. In this review, we have summarized the current research on the applications of multifunctional nanoprobes in image-guided immunotherapy. In addition, image-guided synergistic chemotherapy/photothermal therapy/photodynamic therapy and immunotherapy have also been discussed. Furthermore, the application potential and clinical prospects of multifunctional nanoprobes in combination with immunotherapy have been assessed.

An MRI-trackable therapeutic nanovaccine preventing cancer liver metastasis

Cancer vaccines consisting of tumor-associated antigens (TAAs) can initiate a powerful antitumor immune response through antigen-presenting cells, such as dendritic cells (DCs) and macrophages, and have shown great potential in cancer prevention and therapy. However, poor anticancer efficacy and an uncertain immunization process have hitherto limited the application of cancer vaccines. Herein, a multifunctional nanovaccine comprising ovalbumin (OVA), MnO₂, and polydopamine (OMPN) was prepared by a facile one-pot method. OMPN displayed excellent anticancer efficacy against an orthotopic melanoma and could also prevent liver metastasis in a tumor re-challenge mice model. Additionally, the migration behavior of DCs in the inguinal lymph node after vaccination was tracked by MRI contrasted with OMPN, indicating successful DC activation and immune response. The superior anticancer efficacy, especially the high efficiency against tumor metastasis, and the capability of tracking the immunization process make OMPN a very promising multifunctional nanovaccine for cancer therapy.

Low-Temperature Photothermal Therapy: Strategies and Applications

Although photothermal therapy (PTT) with the assistance of nanotechnology has been considered as an indispensable strategy in the biomedical field, it still encounters some severe problems that need to be solved. Excessive heat can induce treated cells to develop thermal resistance, and thus, the efficacy of PTT may be dramatically decreased. In the meantime, the uncontrollable diffusion of heat can pose a threat to the surrounding healthy tissues. Recently, low-temperature PTT (also known as mild PTT or mild-temperature PTT) has demonstrated its remarkable capacity of conquering these obstacles and has shown excellent performance in bacterial elimination, wound healing, and cancer treatments. Herein, we summarize the recently proposed strategies for achieving low-temperature PTT based on nanomaterials and introduce the synthesis, characteristics, and applications of these nanoplatforms. Additionally, the combination of PTT and other therapeutic modalities for defeating cancers and the synergistic cancer therapeutic effect of the combined treatments are discussed. Finally, the current limitations and future directions are proposed for inspiring more researchers to make contributions to promoting low-temperature PTT toward more successful preclinical and clinical disease treatments.

Injectable polypeptide-engineered hydrogel depot for amplifying the anti-tumor immune effect induced by chemo-photothermal therapy

The immunosuppressive tumor microenvironment has caused great obstacles to tumor immunotherapy, especially where less tumor-associated antigens are released from tumor sites. Herein, a Ag2S QD/DOX/Bestatin@PC10ARGD genetically engineered polypeptide hydrogel PC10ARGD as a sustained-release material was developed for mammary carcinoma treatment. A near-infrared silver sulfide (Ag2S) QD as a photosensitizer was encapsulated into the hydrophobic cavity formed by the self-assembly of the polypeptide nanogel (PC10ARGD) for photothermal therapy. The water-soluble drug DOX and Bestatin were integrated into the PC10ARGD hydrogel. The photothermal effect could trigger the sustained release of the DOX, which could be applied to initiate in situ vaccination. Bestatin as an immune-adjuvant drug could amplify the body's immune function. The results of in vivo therapy tests exhibited that the Ag2S QD/DOX/Bestatin@PC10ARGD hydrogel with laser irradiation could activate anti-tumor immune effects that inhibit the growth of primary tumors and distal lung metastatic nodules. Meanwhile, a safer lower-temperature with multiple laser irradiation treatment strategy exhibited more effective tumor-killing performance (84.4% tumor inhibition rate) and promoted the penetration of immune cells into the tumor tissue. The CD8+ and CD4+ cytotoxic T cells ratio was increased by 5.3 and 10 times, respectively, thus exhibiting a good prognostic signal. The multifunctional polypeptide hydrogel as a green manufacturing and engineering material is promising to serve as a cancer vaccine for anticancer applications.

Temperature-Sensitive Lipid-Coated Carbon Nanotubes for Synergistic Photothermal Therapy and Gene Therapy

The combination of photothermal therapy (PTT) and gene therapy (GT) shows great potential to achieve synergistic anti-tumor activity. However, the lack of a controlled release of genes from carriers remains a severe hindrance. Herein, peptide lipid (PL) and sucrose laurate (SL) were used to coat single-walled carbon nanotubes (SCNTs) and multi-walled carbon nanotubes (MCNTs) to form bifunctional delivery systems (denoted SCNT-PS and MCNT-PS, respectively) with excellent temperature-sensitivity and photothermal performance. CNT/siRNA suppressed tumor growth by silencing survivin expression while exhibiting photothermal effects under near-infrared (NIR) light. SCNT-PS/siRNA showed very high anti-tumor activity, resulting in the complete inhibition of some tumors. It was highly efficient for systemic delivery to tumor sites and to facilitate siRNA release owing to the phase transition of the temperature-sensitive lipids, due to PL and SL coating. Thus, SCNT-PS/siRNA is a promising anti-tumor nanocarrier for combined PTT and GT.

Black phosphorous nanosheet: A novel immune-potentiating nanoadjuvant for near-infrared-improved immunotherapy

Intrinsic immune behaviors of nanomaterials and immune systems promote research on their adjuvanticity and the design of next generation nanovaccine-based immunotherapies. Herein, we report a promising multifunctional nanoadjuvant by exploring the immune-potentiating effects of black phosphorus nanosheets (BPs) in vitro and in vivo. The facile coating of BPs with phenylalanine-lysine-phenylalanine (FKF) tripeptide-modified antigen epitopes (FKF-OVAp@BP) enables the generation of a minimalized nanovaccine by integrating high loading capacity, efficient drug delivery, comprehensive dendritic cell (DC) activation, and biocompatibility for cancer immunotherapy. Systemic immunization elicits potent antitumor cellular immunity and significantly augments checkpoint blockade (CPB) against melanoma in a mouse model. Furthermore, near-infrared (NIR) photothermal effects of BPs create an immune-favorable microenvironment for improved local immunization. This study offers new insight into the integration of immunoactivity and photothermal effects for enhanced cancer immunotherapy by using a nanoadjuvant and thus potentially advances the design and application of multifunctional adjuvant materials for cancer nanotreatment.

Temperature Plays an Essential Regulatory Role in the Tumor Immune Microenvironment

In recent years, emerging immunotherapy has been included in various malignant tumor treatment standards. Temperature has been considered to affect different pathophysiological reactions such as inflammation and cancer for a long time. However, in tumor immunology research, temperature is still rarely considered a significant variable. In this review, we discuss the effects of room temperature, body temperature, and the local tumor temperature on the tumor immune microenvironment from multiple levels and perspectives, and we discuss changes in the body's local and whole-body temperature under tumor conditions. We analyze the current use of ablation treatment-the reason for the opposite immune effect. We should pay more attention to the therapeutic potential of temperature and create a better antitumor microenvironment that can be combined with immunotherapy.

Nanoengineered CAR-T Biohybrids for Solid Tumor Immunotherapy with Microenvironment Photothermal-Remodeling Strategy

Chimeric antigen receptor T cell (CAR-T) therapy has shown remarkable clinical success in eradicating hematologic malignancies. However, hostile microenvironment in solid tumors severely prevents CAR-T cells migrating, infiltrating, and killing. Herein, a nanoengineered CAR-T strategy is reported for enhancing solid tumor therapy through bioorthogonal conjugation with a nano-photosensitizer (indocyanine green nanoparticles, INPs) as a microenvironment modulator. INPs engineered CAR-T biohybrids (CT-INPs) not only retain the original activities and functions of CAR-T cells, but it is further armed with fluorescent tracing and microenvironment remodeling abilities. Irradiated with laser, CT-INPs demonstrate that mild photothermal intervention destroys the extracellular matrix, expanded blood vessels, loosened compact tissue, and stimulated chemokine secretion without damping CAR-T cell activities. Those regulations induce an immune-favorable tumor microenvironment for recruitment and infiltration of CT-INPs. CT-INPs triggered photothermal effects collapse the physical and immunological barriers of solid tumor, and robustly boosted CAR-T immunotherapy. Therefore, CAR-T biohybrids provide reliable treatment strategy for solid tumor immunotherapy via microenvironment reconstruction.

Advances in Nanomaterial-Mediated Photothermal Cancer Therapies: Toward Clinical Applications

Photothermal therapy (PTT) has attracted extensive research attention as a noninvasive and selective treatment strategy for numerous cancers. PTT functions via photothermal effects induced by converting light energy into heat on near-infrared laser irradiation. Despite the great advances in PTT for cancer treatment, the photothermal therapeutics using laser devise only or non-specific small molecule PTT agents has been limited because of its low photothermal conversion efficiency, concerns about the biosafety of the photothermal agents, their low tumor accumulation, and a heat resistance of specific types of cancer. Using nanomaterials as PTT agents themselves, or for delivery of PTT agents, offers improved therapeutic outcomes with fewer side effects through enhanced photothermal conversion efficiency, accumulation of the PTT agent in the tumor tissue, and, by extension, through combination with other therapies. Herein, we review PTT’s current clinical progress and present the future outlooks for clinical applications. To better understand clinical PTT applications, we describe nanomaterial-mediated photothermal effects and their mechanism of action in the tumor microenvironment. This review also summarizes recent studies of PTT alone or in combination with other therapies. Overall, innovative and strategically designed PTT platforms are promising next-generation noninvasive cancer treatments to move closer toward clinical applications.

Bio-Responsive nanoparticle for tumor targeting and enhanced photo-immunotherapy

Despite the potential of immunotherapy in various solid tumors, the efficiency of immunotherapy is limited by little tumor-infiltrating lymphocytes (TILs) and abundant immunosuppressive M2-type tumor-associated macrophages (M2-TAMs) in the tumor microenvironment (TME). Herein, we design a versatile photo-immunotherapy nanoparticle (termed as HA-AuNR/M-M2pep NP) to conquer above challenges. The HA-AuNR/M-M2pep NP is composed of hyaluronic acid modified gold nanorod (HA-AuNR) surface-modified with matrix metalloproteinase-2 (MMP2)-responsive M2pep fusion peptides (M-M2pep). Upon tumor site, the fabricated HA-AuNR/M-M2pep NP releases M2pep through the cleavage of MMP2-sensitive peptide to selectively deplete M2-TAMs and improve immunoactivity of TME. Meanwhile, HA-AuNR could target to tumor cells and realize precise tumor photothermal therapy (PTT) under near infrared light irradiation, which further triggers immunogenic cell death (ICD) of tumor cells and elicits antitumor immunity. In vivo antitumor studies reveal that HA-AuNR/M-M2pep NPs-mediated PTT and M2-TAMs depletion recruit TILs, activate effector T lymphocytes, secrete antitumor cytokines (e.g. IFN-γ, TNF-α), and effectively inhibit the growth of tumor. Collectively, HA-AuNR/M-M2pep NP-mediated photo-immunotherapy based on dual targeted delivery and bio-responsive drug release holds tremendous promise to enhance antitumor efficacy.

Localized NIR-II photo-immunotherapy through the combination of photothermal ablation and in situ generated interleukin-12 cytokine for efficiently eliminating primary and abscopal tumors

Recently, photothermal therapy (PTT) in the second near-infrared (NIR-II) biowindow has emerged as a promising treatment modality; however, its therapeutic outcomes are still limited by heterogeneous heat distribution and insufficient control of metastatic lesions. Tremendous efforts have been made to overcome the PTT's shortcomings by combining PTT with immunotherapy, but unfortunately current strategies still suffer from low response rates, primary/acquired resistance or severe immune-related adverse events. Herein, a novel photothermal agent and gene co-delivery nanoparticle (CSP), with CuS inside the SiO2 pore channels and PDMAEMA polycation on the outside of SiO2 surface, is explored for tumor localized NIR-II PTT and in situ immunotherapy through local generation of IL-12 cytokine. The resulting CSP integrated with the plasmid encoding IL-12 gene (CSP@IL-12) exhibited good gene transfection efficiency, outstanding NIR-II PTT effect and excellent therapeutic outcomes both in vitro and in vivo. Meanwhile, such an in situ joint therapy modality could significantly induce systemic immune responses including promoting DC maturation, CD8+ T cell proliferation and infiltration to efficiently eliminate possible metastatic lesions through abscopal effects. Hence, this creative combinational strategy of NIR-II PTT and IL-12 cytokine therapy might provide a more efficient, controllable and safer alternative strategy for future photo-immunotherapy.

Recent Progress in the Synergistic Combination of Nanoparticle-Mediated Hyperthermia and Immunotherapy for Treatment of Cancer

Immunotherapy has demonstrated great clinical success in certain cancers, driven primarily by immune checkpoint blockade and adoptive cell therapies. Immunotherapy can elicit strong, durable responses in some patients, but others do not respond, and to date immunotherapy has demonstrated success in only a limited number of cancers. To address this limitation, combinatorial approaches with chemo- and radiotherapy have been applied in the clinic. Extensive preclinical evidence suggests that hyperthermia therapy (HT) has considerable potential to augment immunotherapy with minimal toxicity. This progress report will provide a brief overview of immunotherapy and HT approaches and highlight recent progress in the application of nanoparticle (NP)-based HT in combination with immunotherapy. NPs allow for tumor-specific targeting of deep tissue tumors while potentially providing more even heating. NP-based HT increases tumor immunogenicity and tumor permeability, which improves immune cell infiltration and creates an environment more responsive to immunotherapy, particularly in solid tumors.

Modulating the Tumour Microenvironment by Intratumoural Injection of Pattern Recognition Receptor Agonists

Signalling through pattern recognition receptors (PRRs) leads to strong proinflammatory responses, enhancing the activity of antigen presenting cells and shaping adaptive immune responses against tumour associated antigens. Unfortunately, toxicities associated with systemic administration of these agonists have limited their clinical use to date. Direct injection of PRR agonists into the tumour can enhance immune responses by directly modulating the cells present in the tumour microenvironment. This can improve local antitumour activity, but importantly, also facilitates systemic responses that limit tumour growth at distant sites. As such, this form of therapy could be used clinically where metastatic tumour lesions are accessible, or as neoadjuvant therapy. In this review, we summarise current preclinical data on intratumoural administration of PRR agonists, including new strategies to optimise delivery and impact, and combination studies with current and promising new cancer therapies.

Few-Layer Bismuthene for Checkpoint Knockdown Enhanced Cancer Immunotherapy with Rapid Clearance and Sequentially Triggered One-for-All Strategy

As a conceptually attractive strategy, the use of immune checkpoint blockade antibodies to treat cancer is limited due to the restrained tumor-infiltrating lymphocytes (TILs), poor accumulation and penetration of antibodies, and deficient checkpoint blockade in malignancies. In this study, we describe a pH and mild photothermal sequentially triggered PD-L1 siRNA release nanosystem, based on monoelemental bismuthene, as a one-for-all strategy to realize enhanced tumor mild photothermal immunotherapy. Under manually controlled NIR irradiation, the bismuthene-based nanosystem simultaneously induces a tumor-enhanced pathological permeability and retention (EPPR) effect, increases TIL recruitment, and triggers programmed siRNA release, thereby amplifying anti-PD-L1 immunotherapy. In addition, the nanosystem's rapid removal through intestinal and renal clearance mitigates toxicity risk associated with long-term retention. In vivo antitumor experiments demonstrate that this bismuthene-based nanosystem is a promising and effective approach for "cold" tumor management.

Nanomaterial-Based Tumor Photothermal Immunotherapy

In recent years, photothermal therapy (PTT) particularly nanomaterial-based PTT is a promising therapeutic modality and technique for cancer tumor ablation. In addition to killing tumor cells directly through heat, PTT also can induce immunogenic cell death (ICD) to activate the whole-body anti-tumor immune response, including the redistribution and activation of immune effector cells, the expression and secretion of cytokines and the transformation of memory T lymphocytes. When used in combination with immunotherapy, the efficacy of nanomaterial-based PTT can be improved. This article summarized the mechanism of nanomaterial-based PTT against cancer and how nanomaterial-based PTT impacts the tumor microenvironment and induces an immune response. Moreover, we reviewed recent advances of nanomaterial-based photothermal immunotherapy and discussed challenges and future outlook.

Biodegradable pH-responsive amorphous calcium carbonate nanoparticles as immunoadjuvants for multimodal imaging and enhanced photoimmunotherapy

Development of bioresponsive theranostic nanoparticles to enhance cancer diagnostics and control cancer metastasis is highly desirable. In this study, we developed such a bioresponsive theranostic nanoparticle for synergistic photoimmunotherapy. In particular, these nanoparticles were constructed by embedding indocyanine green (ICG) into Mn2+-doped amorphous calcium carbonate (ACC(Mn)) nanoparticles, followed by loading of the Toll-like-receptor-7 agonist imiquimod (IMQ). The IMQ@ACC(Mn)-ICG/PEG nanoparticles respond to the acidic pH of the tumor microenvironment (TME) and co-deliver ICG and IMQ into the tumor. Selective phototherapy was achieved upon activation using a near-infrared laser. In the presence of IMQ and arising from phototherapeutically treated tumor cells, tumor-associated antigens give rise to a strong antitumor immune response. Reversal of the immunosuppressive TME via H+ scavenging of the tumor through ACC nanoparticles effectively inhibits tumor metastases. Moreover, the combination of ICG and Mn2+ also serves as an advanced contrast agent for cancer multimode imaging. Overall, these bioresponsive nanoparticles provide a promising approach for cancer theranostics with promising potential for future clinical translation.

Nanomedicine-based tumor photothermal therapy synergized immunotherapy

The emerging anti-tumor immunotherapy has made significant progress in clinical application. However, single immunotherapy is not effective for all anti-tumor treatments, owing to the low objective response rate and the risk of immune-related side effects. Meanwhile, photothermal therapy (PTT) has attracted significant attention because of its non-invasiveness, spatiotemporal controllability and small side effects. Combining PTT with immunotherapy overcomes the issue that single photothermal therapy cannot eradicate tumors with metastasis and recurrence. However, it improves the therapeutic effect of immunotherapy, as the photothermal therapy usually promotes release of tumor-related antigens, triggers immune response by the immunogenic cell death (ICD), thereby, endowing unique synergistic mechanisms for cancer therapy. This review summarizes recent research advances in utilizing nanomedicines for PTT in combination with immunotherapy to improve the outcome of cancer treatment. The strategies include immunogenic cell death, immune agonists and cancer vaccines, immune checkpoint blockades and tumor specific monoclonal antibodies, and small-molecule immune inhibitors. The combination of synergized PTT-immunotherapy with other therapeutic strategies is also discussed.

Persistent Regulation of Tumor Hypoxia Microenvironment via a Bioinspired Pt-Based Oxygen Nanogenerator for Multimodal Imaging-Guided Synergistic Phototherapy

Multifunctional nanoplatforms for imaging-guided synergistic antitumor treatment are highly desirable in biomedical applications. However, anticancer treatment is largely affected by the pre-existing hypoxic tumor microenvironment (TME), which not only causes the resistance of the tumors to photodynamic therapy (PDT), but also promotes tumorigenesis and tumor progression. Here, a continuous O2 self-enriched nanoplatform is constructed for multimodal imaging-guided synergistic phototherapy based on octahedral gold nanoshells (GNSs), which are constructed by a more facile and straightforward one-step method using platinum (Pt) nanozyme-decorated metal-organic frameworks (MOF) as the inner template. The Pt-decorated MOF@GNSs (PtMGs) are further functionalized with human serum albumin-chelated gadolinium (HSA-Gd, HGd) and loaded with indocyanine green (ICG) (ICG-PtMGs@HGd) to achieve a synergistic PDT/PTT effect and fluorescence (FL)/multispectral optoacoustic tomography (MSOT)/X-ray computed tomography (CT)/magnetic resonance (MR) imaging. The Pt-decorated nanoplatform endows remarkable catalase-like behavior and facilitates the continuous decomposition of the endogenous H2O2 into O2 to enhance the PDT effect under hypoxic TME. HSA modification enhances the biocompatibility and tumor-targeting ability of the nanocomposites. This TME-responsive and O2 self-supplement nanoparticle holds great potential as a multifunctional theranostic nanoplatform for the multimodal imaging-guided synergistic phototherapy of solid tumors.

Palladium-based nanomaterials for cancer imaging and therapy

In recent decade, palladium-based (Pd-based) nanomaterials have shown significant potential for biomedical applications because of their unique optical properties, excellent biocompatibility and high stability in physiological environment. Compared with other intensively studied noble nanomaterials, such as gold (Au) and silver (Ag) nanomaterials, research on Pd-based nanomaterials started late, but the distinctive features, such as high photothermal conversion efficiency and high photothermal stability, have made them getting great attention in the field of nanomedicine. The goal of this review is to provide a comprehensive and critical perspective on the recent progress of Pd-based nanomaterials as imaging contrast agents and therapeutic agents. The imaging section focuses on applications in photoacoustic (PA) imaging, single-photon emission computed tomography (SPECT) imaging, computed tomography (CT) imaging and magnetic resonance (MR) imaging. For treatment of cancer, single photothermal therapy (PTT) and PTT combined with other therapeutic modalities will be discussed. Finally, the safety concerns, forthcoming challenges and perspective of Pd-based nanomaterials on biomedical applications will be presented.

Ca2+-Mediated Surface Polydopamine Engineering to Program Dendritic Cell Maturation

Engineering of cell surfaces holds promise in manipulating cellular activities in a physicochemical route as a complement to the biological approach. Mediated by Ca²⁺, a quick and convenient yet cytocompatible method is used to achieve surface engineering, by which polydopamine nanostructures can be in situ grown onto dendritic cell (DC) surfaces within 10 min. Ca²⁺, as the physical bridge between the negative cell surface and polydopamine, avoids the direct chemical polymerization of polydopamine onto the cell surface, critically important to maintain the cell viability. As a proof of concept in potential applications, this cell surface engineering shows a good control toward DC maturation. Upon surface polydopamine engineering, bone-marrow-derived DC exhibits a unique bidirectional control of maturation. The polydopamine structure enables effective suppression of DC activation by acting as an efficient scavenger of reactive oxygen species, a key signal during maturation. Conversely, an 808 nm laser irradiation can remotely relieve the suppressed state and effectively activate DC maturation by the photoheat effect of polydopamine (39 °C). The work provides an easily implemented, straightforward approach to achieve cell surface engineering, through which the DC maturation can be controlled.

Molecular and nanoengineering approaches towards activatable cancer immunotherapy

This review summarizes the development of activatable immunotherapeutic nanoagents that activate antitumor immunity only in response to internal or external stimuli, which potentially enhance patient response rates while reducing immune-related adverse events during cancer immunotherapy.

Integration of immunogenic activation and immunosuppressive reversion using mitochondrial-respiration-inhibited platelet-mimicking nanoparticles

Here, we developed platelet membranes (PM) as nano-carriers to co-encapsulate metformin (Met) and IR780 (PM-IR780-Met NPs). The resulting nano-carrier ensured a longer circulation lifetime and facilitated the greater accumulation of IR780 and Met in tumors owing to the active adhesion between PM and tumor cells. As a photodynamic therapy (PDT) agent, IR780 could effectively kill the tumor by producing toxic reactive singlet oxygen species (ROS), while the introduction of Met inhibited mitochondrial respiration and reduced tumor oxygen consumption, thereby evoking an oxygen-boosted PDT and propelling the immunogenic cell death (ICD)-based immunogenic pathway. Meanwhile, the reversed tumor hypoxia also impeded the myeloid derived suppressor cell (MDSC)-regulated immunosuppressive pathway. Finally, tremendous T cells were recruited and activated, providing a promising platform to eliminate the primary tumors and synchronously opening a new avenue for the effective ablation of tumor metastasis.

Amplified Cancer Immunotherapy of a Surface-Engineered Antigenic Microparticle Vaccine by Synergistically Modulating Tumor Microenvironment

Efficient cancer vaccines not only require the co-delivery of potent antigens and highly immunostimulatory adjuvants to initiate robust tumor-specific host immune response but also solve the spatiotemporal consistency of host immunity and tumor microenvironment (TME) immunomodulation. Here, we designed a biomaterials-based strategy for converting tumor-derived antigenic microparticles (T-MPs) into a cancer vaccine to meet this conundrum and demonstrated its therapeutic potential in multiple murine tumor models. The internal cavity of T-MPs was employed to store nano-Fe₃O₄ (Fe₃O₄/T-MPs), and then dense adjuvant CpG-loaded liposome arrays (CpG/Lipo) were tethered on the surface of Fe₃O₄/T-MP through mild surface engineering to get a vaccine (Fe₃O₄/T-MPs-CpG/Lipo), demonstrating that co-delivery of Fe₃O₄/T-MPs and CpG/Lipo to antigen presenting cells (APCs) could elicit strong tumor antigen-specific host immune response. Meanwhile, vaccines distributed in the TME could reverse infiltrated tumor-associated macrophages into a tumor-suppressive M1 phenotype by nano-Fe₃O₄, amazingly induce abundant infiltration of cytotoxic T lymphocytes, and transform a "cold" tumor into a "hot" tumor. Furthermore, amplified antitumor immunity was realized by the combination of an Fe₃O₄/T-MPs-CpG/Lipo vaccine and immune checkpoint PD-L1 blockade, specifically inhibiting ∼83% of the progression of B16F10-bearing mice and extending the median survival time to 3 months. Overall, this study synergistically modulates the tumor immunosuppressive network and host antitumor immunity in a spatiotemporal manner, which suggests a general cell-engineering strategy tailored to a personalized vaccine from autologous cancer cell materials of each individual patient.