A trustworthy CpG nanoplatform for highly safe and efficient cancer photothermal combined immunotherapy

A review of carbohydrate polymer-synthesized nanoparticles in cancer immunotherapy: Past, present and future perspectives

Cancer continues to be a leading factor in mortality and tackling it has been made difficult by the development of immune escape. Furthermore, alternative treatments like surgery, chemotherapy, and radiation have been unsuccessful in eradicating cancer. Despite being effective, they have not succeeded in providing a full cancer treatment and exhibit several negative effects. The field of immunotherapy has been improved by utilizing cancer vaccines, immune checkpoint inhibitors (ICIs), and adoptive cell transfer to enhance immune responses to tumors. Nevertheless, cancer cells need to adapt and become immune to immune reactions, leading to the need for innovative treatment methods. Carbohydrate polymers and their nanoparticles have been beneficial in improving cancer immunotherapy by being customizable to specifically target the immune system. These nanoparticles can change the tumor microenvironment and accelerate immunotherapy by affecting immune cells such as T cells and dendritic cells. Incorporating both chemotherapy and phototherapy into nanoparticles can improve immunotherapy. Furthermore, besides controlling immune reactions, carbohydrate polymer nanoparticles can also be used for theranostic purposes, where they are used to image tumor cells and activate the immune system to eradicate cancer.

Nanomaterial-assisted delivery of CpG oligodeoxynucleotides for boosting cancer immunotherapy

Cancer immunotherapy aims to improve immunity to not only eliminate the primary tumor but also inhibit metastasis and recurrence. It is considered an extremely promising therapeutic approach that breaks free from the traditional paradigm of oncological treatment. As the medical community learns more about the immune system's mechanisms that "turn off the brake" and "step on the throttle", there is increasingly successful research on immunomodulators. However, there are still more restrictions than countermeasures with immunotherapy related to immunomodulators, such as low responsiveness and immune-related adverse events that cause multiple adverse reactions. Therefore, medical experts and materials scientists attempted to the efficacy of immunomodulatory treatments through various methods, especially nanomaterial-assisted strategies. CpG oligodeoxynucleotides (CpG) not only act as an adjuvant to promote immune responses, but also induce autophagy. In this review, the enhancement of immunotherapy using nanomaterial-based CpG formulations is systematically elaborated, with a focus on the delivery, protection, synergistic promotion of CpG efficacy by nanomaterials, and selection of the timing of treatment. In addition, we also discuss and prospect the existing problems and future directions of research on nanomaterials in auxiliary CpG therapy.

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.

Glycogen for lysosome-targeted CpG ODNs delivery and enhanced cancer immunotherapy

CpG oligodeoxynucleotides (ODNs) strongly activate the immune system after binding to toll-like receptor 9 (TLR9) in lysosome, which demonstrated significant potential in cancer immunotherapy. However, their therapeutic efficacy is limited by drawbacks such as rapid degradation and poor cellular uptake. Although encouraging progress have been made on developing various delivery systems for CpG ODNs, safety risks of the synthetic nanocarriers as well as the deficient CpG ODNs release within lysosome remain big obstacles. Herein, we developed a novel nanovector for lysosome-targeted CpG ODNs delivery and enhanced cancer immunotherapy. Natural glycogen was simply aminated (NH2-Gly) through grafting with diethylenetriamine (DETA), which was spherical in shape with diameter of approximately 40 nm. NH2-Gly possessed good biocompatibility. Cationic NH2-Gly complexed CpG ODNs well and protected them from nuclease digestion. NH2-Gly significantly enhanced the cellular uptake of CpG ODNs. Efficient CpG ODNs release was observed in the presence of α-glucosidase that mimicking the environment of lysosome. Consequently, NH2-Gly/CpG complexes triggered potent antitumor immunity and effectively inhibit the tumor growth without causing any toxic effect or tissue damages. This work highlights the promise of glycogen for lysosome-targeted on-command delivery of CpG ODNs, which brings new hope for precision cancer immunotherapy.

Aminated yeast β-D-glucan for macrophage-targeted delivery of CpG oligodeoxynucleotides and synergistically enhanced cancer immunotherapy

CpG oligodeoxynucleotides (CpG ODNs) activate immune system and show strong potential in cancer immunotherapy. However, therapeutic efficacy of CpG ODNs is hampered due to rapid nuclease degradation and insufficient cellular uptake. Delivery of CpG ODNs into antigen presenting cells (APCs) is vital to enhance their therapeutic efficacy. Herein, we developed a super-convenient yet efficient strategy for macrophage-targeted delivery of CpG ODNs and synergistically enhanced cancer immunotherapy. Aminated yeast β-D-glucan (NH2-Glu) was simply synthesized through functionalization of β-D-glucan with DETA, which exhibited a dendrimer-like shape with size of about 80 nm. NH2-Glu complexed negatively-charged CpG ODNs. The as-prepared NH2-Glu/CpG complexes were positively charged, uniformly dispersed and exhibited good stability against nuclease degradation. Due to the specific recognition with dectin-1 expressed on macrophages, NH2-Glu/CpG complexes targeted macrophage and exhibited significantly enhanced cellular uptake due to dectin-1-mediated endocytosis. NH2-Glu/CpG complexes showed potent immunostimulatory activity. Contributed by the inherent immunostimulatory and antitumor activity, yeast β-D-glucan functioned synergistically with CpG ODNs in inducing antitumor immunity. NH2-Glu/CpG complexes remarkably inhibited tumor growth without causing toxic effect. In summary, this work provides a facile yet efficient macrophage-targeted CpG ODNs delivery system for cancer immunotherapy.

Cationic Starch Nanoparticles for Enhancing CpG Oligodeoxynucleotide-Mediated Antitumor Immunity

CpG ODNs demonstrate a significant promise for immunotherapy. However, their application is limited owing to quick DNase digestion and inadequate cellular internalization. Transportation of CpG ODNs into immune cells is crucial. Although viral vectors exhibit high transfection efficiency, safety risks, high cost, and low carrying capacity remain big obstacles. Herein, a novel CpG ODNs vector was fabricated by using starch. Starch was ultrasonicated and simply aminated (NH2-St) through grafting with diethylenetriamine, which was spherical with a diameter of 50 nm. NH2-St possessed good biocompatibility. Cationic NH2-St encapsulated CpG ODNs well and possessed a high loading capacity of 317 μg/mg. NH2-St protected CpG ODNs from nuclease digestion and significantly enhanced their cellular uptake. NH2-St/CpG induced the potent secretion of antitumor cytokines from macrophages and effectively suppressed the growth of tumor cells. This work highlights the promise of starch for CpG ODNs delivery, which brings new hope for cancer immunotherapy.

Meta-Analysis of Nanoparticle Distribution in Tumors and Major Organs in Tumor-Bearing Mice

Low tumor delivery efficiency is a critical barrier in cancer nanomedicine. This study reports an updated version of "Nano-Tumor Database", which increases the number of time-dependent concentration data sets for different nanoparticles (NPs) in tumors from the previous version of 376 data sets with 1732 data points from 200 studies to the current version of 534 data sets with 2345 data points from 297 studies published from 2005 to 2021. Additionally, the current database includes 1972 data sets for five major organs (i.e., liver, spleen, lung, heart, and kidney) with a total of 8461 concentration data points. Tumor delivery and organ distribution are calculated using three pharmacokinetic parameters, including delivery efficiency, maximum concentration, and distribution coefficient. The median tumor delivery efficiency is 0.67% injected dose (ID), which is low but is consistent with previous studies. Employing the best regression model for tumor delivery efficiency, we generate hypothetical scenarios with different combinations of NP factors that may lead to a higher delivery efficiency of >3%ID, which requires further experimentation to confirm. In healthy organs, the highest NP accumulation is in the liver (10.69%ID/g), followed by the spleen 6.93%ID/g and the kidney 3.22%ID/g. Our perspective on how to facilitate NP design and clinical translation is presented. This study reports a substantially expanded "Nano-Tumor Database" and several statistical models that may help nanomedicine design in the future.

Regulating the surface topography of CpG nanoadjuvants via coordination-driven self-assembly for enhanced tumor immunotherapy

Immunoadjuvants play a key role in enhancing the efficacy of therapeutic tumor vaccines for treating malignant and recurrent cancers. However, due to the bottleneck in the rational design and mechanistic understanding of novel adjuvants, currently available immunoadjuvants in clinical practice are very limited. To boost adjuvant design and development, herein we propose a surface topography regulatory strategy for constructing novel adjuvants with improved adjuvant properties. One of the licensed adjuvants with a well-defined molecular mechanism of immune activation, cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODNs), was used as the material framework. We constructed immunostimulatory CpG nanoparticles (CpG NPs) with different surface topographies by coordination-driven self-assembly between CpG ODNs and ferrous ions. These self-assembled CpG NPs combine the biological and physical activation abilities of innate immunity and can be used as adjuvants of tumor antigens for malignant tumor immunotherapy. The experimental results showed that these CpG NPs could rapidly enter innate immune cells and remold the tumor microenvironment (TME) to enhance anti-tumor immunotherapy via (i) inducing proinflammatory cytokine production; (ii) promoting the transformation of macrophages from immunosuppressed M2 types into immunoactivated M1 types; (iii) amplifying the antigen presentation of mature dendritic cells (DCs), and (iv) activating T cells in tumor sites. Among the prepared nanostructures, pompon-shaped nanoparticles (NPpo) showed the strongest adjuvant properties and anti-tumor immunotherapeutic effect as the adjuvant of ovalbumin in melanoma-bearing mice. Overall, this work provides an effective strategy for designing novel adjuvants for activating the immunosuppressed TME to enable better cancer immunotherapy.

Yeast β-D-glucan functionalized graphene oxide for macrophage-targeted delivery of CpG oligodeoxynucleotides and synergistically enhanced antitumor immunity

Immunostimulatory CpG oligodeoxynucleotides (CpG ODNs) show strong potential in cancer immunotherapy. However, therapeutic efficacy of CpG ODNs is hindered due to rapid nuclease degradation and insufficient cellular uptake. Transfecting CpG ODNs into antigen presenting cells (APCs) is vital to enhance their therapeutic efficacy while reduce the potential side effects. Herein, a multifunctional CpG ODNs vector was fabricated through functionalization of graphene oxide (GO) with yeast β-D-glucan, and its potential in cancer immunotherapy was further investigated. GO-β-D-glucan protected CpG ODNs from nuclease digestion. β-D-glucan endowed the delivery system with targeting ability for macrophage due to its recognition with dectin-1. Thus, GO-β-D-glucan enhanced the delivery of CpG ODNs into RAW264.7 cells due to dectin-1-mediated endocytosis. More importantly, β-D-glucan functioned synergistically with CpG ODNs in inducing antitumor immunity. GO-β-D-glucan/CpG ODNs inhibited the tumor cells growth more effectively. This work provides a macrophage-targeted CpG ODNs delivery system for cancer immunotherapy. Graphic abstract.

Recent advances in 2D material-based phototherapy

Phototherapy, which generally refers to photothermal therapy (PTT) and photodynamic therapy (PDT), has received significant attention over the past few years since it is non-invasive, has effective selectivity, and has few side effects. As a result, it has become a promising alternative to traditional clinical treatments. At present, two-dimensional materials (2D materials) have proven to be at the forefront of the development of advanced nanomaterials due to their ultrathin structures and fascinating optical properties. As a result, much work has been put into developing phototherapy platforms based on 2D materials. This review summarizes the current developments in 2D materials beyond graphene for phototherapy, focusing on the novel approaches of PTT and PDT. New methods are being developed to go above and beyond conventional treatment to fully use the potential of 2D materials. Additionally, the efficacy of cutting-edge phototherapy is assessed, and the existing difficulties and future prospects of 2D materials for phototherapy are covered.

Immunoinducible Carbon Dot-Incorporated Hydrogels as a Photothermal-Derived Antigen Depot to Trigger a Robust Antitumor Immune Response

Immunogenic tumor cell death (ICD) induced by photothermal therapy (PTT) fails to elicit a robust antitumor immune response partially due to its inherent immunosuppressive microenvironment and poor antigen presentation. To address these issues, we developed an immunoinducible carbon dot-incorporated hydrogel (iCD@Gel) through a dynamic covalent Schiff base reaction using mannose-modified aluminum-doped carbon dots (M/A-CDs) as a cross-linking agent. The M/A-CDs possessed superior photothermal conversion efficiency and served as nanocarriers to load cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODNs) for inducing the maturation of dendritic cells (DCs) via mannose receptor-mediated targeting delivery. Upon intratumoral injection, the as-prepared iCD@Gel induced ICD, and damage-associated molecular patterns (DAMPs) were released via photothermal ablation under 808 nm NIR irradiation. Subsequently, the iCD@Gel synergized with the DAMPs to significantly promote the maturation and antigen cross-presentation ability of DCs. This work provides a promising strategy to develop carbon dot-based therapeutic hydrogels for photothermal therapy and immune activation.

Sea Cucumber Derived Triterpenoid Glycoside Frondoside A: A Potential Anti-Bladder Cancer Drug

Bladder cancer is a highly recurrent disease and a common cause of cancer-related deaths worldwide. Despite recent developments in diagnosis and therapy, the clinical outcome of bladder cancer remains poor; therefore, novel anti-bladder cancer drugs are urgently needed. Natural bioactive substances extracted from marine organisms such as sea cucumbers, scallops, and sea urchins are believed to have anti-cancer activity with high effectiveness and less toxicity. Frondoside A is a triterpenoid glycoside isolated from sea cucumber, Cucumaria frondosa. It has been demonstrated that Frondoside A exhibits anti-proliferative, anti-invasive, anti-angiogenic, anti-cancer, and potent immunomodulatory effects. In addition, CpG oligodeoxynucleotide (CpG-ODN) has also been shown to have potent anti-cancer effects in various tumors models, such as liver cancer, breast cancer, and bladder cancer. However, very few studies have investigated the effectiveness of Frondoside A against bladder cancer alone or in combination with CpG-ODN. In this study, we first investigated the individual effects of both Frondoside A and CpG-ODN and subsequently studied their combined effects on human bladder cancer cell viability, migration, apoptosis, and cell cycle in vitro, and on tumor growth in nude mice using human bladder cancer cell line UM-UC-3. To interrogate possible synergistic effects, combinations of different concentrations of the two drugs were used. Our data showed that Frondoside A decreased the viability of bladder cancer cells UM-UC-3 in a concentration-dependent manner, and its inhibitory effect on cell viability (2.5 μM) was superior to EPI (10 μM). We also showed that Frondoside A inhibited UM-UC-3 cell migration, affected the distribution of cell cycle and induced cell apoptosis in concentration-dependent manners, which effectively increased the sub-G1 (apoptotic) cell fraction. In addition, we also demonstrated that immunomodulator CpG-ODN could synergistically potentiate the inhibitory effects of Frondoside A on the proliferation and migration of human bladder cancer cell line UM-UC-3. In in vivo experiments, Frondoside A (800 μg/kg/day i.p. for 14 days) alone and in combination with CpG-ODN (1 mg/kg/dose i.p.) significantly decreased the growth of UM-UC-3 tumor xenografts, without any significant toxic side-effects; however, the chemotherapeutic agent EPI caused weight loss in nude mice. Taken together, these findings indicated that Frondoside A in combination with CpG-ODN is a promising therapeutic strategy for bladder cancer.

Nanostructures as Photothermal Agents in Tumor Treatment

Traditional methods of tumor treatment such as surgical resection, chemotherapy, and radiation therapy have certain limitations, and their treatment effects are not always satisfactory. As a new tumor treatment method, photothermal therapy based on nanostructures has attracted the attention of researchers due to its characteristics of minimally invasive, low side effects, and inhibition of cancer metastasis. In recent years, there has been a variety of inorganic or organic nanostructures used in the field of photothermal tumor treatment, and they have shown great application prospects. In this paper, the advantages and disadvantages of a variety of nanomaterials/nanostructures as photothermal agents (PTAs) for photothermal therapy as well as their research progress are reviewed. For the sake of clarity, the recently reported nanomaterials/nanostructures for photothermal therapy of tumor are classified into five main categories, i.e., carbon nanostructures, noble metal nanostructures, transition metal sulfides, organic polymer, and other nanostructures. In addition, future perspectives or challenges in the related field are discussed.

Tumor immunosuppressive microenvironment modulating hydrogels for second near-infrared photothermal-immunotherapy of cancer

Immunotherapy has recently been seen as a hopeful therapeutic device to inhibit tumor growth and metastasis, while the curative efficacy is limited by intrinsic immunosuppressive tumor microenvironment. Herein, we reported a tumor immunosuppressive microenvironment modulating hydrogel (TIMmH) platform to achieve second near-infrared (NIR-II) photothermal therapy (PTT) combined immunotherapy for durable inhibition of breast cancer. This TIMmH platform was synthesized through co-loading of NIR-II photothermal nanoagent and an immunoadjuvant cytosine-phosphateguanosine oligodeoxynucleotides (CpG ODNs) into the alginate hydrogel (ALG). Upon the administration of ALG into the tumor, the TIMmH was in situ formed via the coordination effect with Ca²⁺, locally encapsulating the semiconducting polymer nanoparticles (SP_IIN) and CpG in the colloid, achieving to prolong the accumulation time and prevent the premature damage and release of immunotherapeutic agents. Upon 1064-nm photoirradiation, the TIMmH_SD was able to elevate the intratumoral temperature for the ablation of tumors, which could induce the apoptosis of tumor cells and achieve thermal immune activation by regulating of an immunosuppressive microenvironment. The TIMmH-mediated combined treatment effectively suppressed the growths of breast cancers, and even acquired a sustained inhibition of the lung metastasis. This study provides a novel tumor immunosuppressive microenvironment modulating hydrogel platform with NIR-II photoexcited capacity for the safe, effective and durable lung metastasis-inhibiting breast cancer treatment.

68Ga-labeled dendrimer-entrapped gold nanoparticles for PET/CT dual-modality imaging and immunotherapy of tumors

The design and fabrication of nanoplatforms with both nuclear medical imaging and therapeutic functions remain challenging in current precision nanomedicine. Herein, we report the design of a novel nanoplatform based on glucose-modified dendrimer-entrapped gold nanoparticles (Au DENPs) labeled with radionuclide ⁶⁸Ga and incorporated with cytosine-guanine (CpG) oligonucleotide for positron emission tomography (PET)/computed tomography (CT) dual-mode imaging and immunotherapy of tumors. In this study, generation 5 poly(amidoamine) (PAMAM) dendrimers were first modified to have 8.2 DOTA and 7.3 polyethylene glycol with the other end functionalized with 2-amino-2-deoxy-D-glucose (DG) for each dendrimer, entrapped with Au NPs, and then radiolabeled with ⁶⁸Ga through the DOTA chelation. The synthesized DG-Au DENPs have good cytocompatibility, targeting specificity toward cancer cells expressing glucose transporters, and the ability to be labeled by ⁶⁸Ga with great labeling efficiency (≥85%) and stability (≥95%). After being loaded with CpG, the formed DG-Au DENPs/CpG polyplexes were proven to be used for tumor dual-mode PET/CT imaging and immunotherapy by effectively maturing dendritic cells to initiate a T cell-based antitumor immune response in vivo. Compared with the DG-free polyplexes, the developed DG-Au DENPs/CpG polyplexes show a much more sensitive imaging effect and better inhibition effect of tumors. These findings demonstrate a unique design of ⁶⁸Ga-labeled DG-Au DENPs, a promising theranostic nanoplatform that may be extended to tackle different tumor types.

ApoE-mediated systemic nanodelivery of granzyme B and CpG for enhanced glioma immunotherapy

The response of malignant glioma to immunotherapy remains gloomy due to its discrete immunological environment and poor brain penetration of immunotherapeutic agents. Here, we disclose that ApoE peptide-mediated systemic nanodelivery of granzyme B (GrB) and CpG ODN co-stimulates enhanced immunotherapy of murine malignant LCPN glioma model. ApoE peptide-functionalized polymersomes encapsulating GrB (ApoE-PS-GrB) could effectively penetrate the blood-brain barrier-mimicking endothelial cell monolayer in vitro and further be taken up by LCPN cells, inducing strong immunogenic cell death (ICD). The co-administration of ApoE-PS-GrB and ApoE-PS-CpG in orthotopic LCPN glioma-bearing mice co-stimulated cytokine production, maturation of dendritic cells (DCs), infiltration of cytotoxic T lymphocytes (CTLs) while reduction of regulatory T lymphocytes (T_reg) and M2 phenotype macrophages in the tumor microenvironment, leading to greatly delayed tumor progression and significantly prolonged survival time compared with all controls. The ApoE-mediated systemic nanodelivery of GrB and CpG ODN opens a new pathway for potent immunotherapy of malignant glioma.

Microfluidic Synthesis of Block Copolymer Micelles: Application as Drug nanocarriers and as Photothermal Transductors When Loading Pd Nanosheets

The synthesis of polymeric nanoparticles from a block copolymer based on poly(ethylene glycol) and a polymethacrylate containing the nucleobase analogue 2,6-diacylaminopyridine has been optimized by microfluidics to obtain homogeneous spherical micelles. Loading and delivery properties have been studied using naproxen as a model. The incorporation of a Pd precursor in the polymer organic solution fed into the micromixer allows the preparation of Pd(II) precursor-polymer hybrid systems, and the subsequent reduction with CO lead to the in-situ synthesis of Pd nanosheets inside of the hydrophobic core of the polymeric micelles. This methodology is highly efficient to yield all polymeric nanoparticles loaded with Pd nanosheets as detected by electron microscopy and energy-dispersive X-ray spectroscopy. The cell viability of these Pd nanosheets-containing polymeric nanoparticles has been evaluated using five cell lines, showing a high cytocompatibility at the tested concentrations without detrimental effects in cell membrane and nuclei. Furthermore, the use of these hybrid polymeric nanoparticles as photothermal transductors has been evaluated using NIR as irradiation source, as well as its application in photothermal therapy using different cell lines demonstrating a high efficiency in all cell cultures. This article is protected by copyright. All rights reserved.

Recent Advance of Nanomaterial-Mediated Tumor Therapies in the Past Five Years

Cancer has posed a major threat to human life and health with a rapidly increasing number of patients. The complexity and refractory of tumors have brought great challenges to tumor treatment. In recent years, nanomaterials and nanotechnology have attracted more attention and greatly improved the efficiency of tumor therapies and significantly prolonged the survival period, whether for traditional tumor treatment methods such as radiotherapy, or emerging methods, such as phototherapy and immunotherapy, sonodynamic therapy, chemodynamic therapy and RNA interference therapeutics. Various monotherapies have obtained positive results, while combination therapies are further proposed to prevent incomplete eradication and recurrence of tumors, strengthen tumor killing efficacy with minimal side effects. In view of the complementary promotion effects between different therapies, it is vital to utilize nanomaterials as the link between monotherapies to achieve synergistic performance. Further development of nanomaterials with efficient tumor-killing effect and better biosafety is more in line with the needs of clinical treatment. In a word, the development of nanomaterials provides a promising way for tumor treatment, and here we will review the emerging nanomaterials towards radiotherapy, phototherapy and immunotherapy, and summarized the developed nanocarriers applied for the tumor combination therapies in the past 5 years, besides, the advances of some other novel therapies such as sonodynamic therapy, chemodynamic therapy, and RNA interference therapeutics have also been mentioned.

Polydopamine-based nanoplatform for photothermal ablation with long-term immune activation against melanoma and its recurrence

The high risk of tumor recurrence presents a big challenge in melanoma therapy. Photothermal therapy (PTT) has merged as a powerful weapon against tumor in recent years, which produces tumor-associated antigens (TAA) and recruits dendritic cells (DCs) to tumor sites through immunogenic cell death (ICD) for immune activation. However, due to the lack of activation signals of DCs, the immune effect induced by PTT is not sufficient to inhibit the recurrence and proliferation of tumor. To efficiently cooperate PTT and immunotherapy to circumvent tumor recurrence, here we constructed a polydopamine (PDA) based core-shell nanoplatform loading CpG ODNs to elicit robust photothermal ablation and antitumor immune responses. Cationized polydopamine coated with hyaluronic acid (HA) shell was proven an efficient photothermal agent that increased the surface temperature of tumor by 16 °C and induced ICD. CpG ODNs effectively induced maturation of DCs by elevating the expression of co-stimulating markers. PTT combined with CpG ODNs achieved a remarkable synergistic treatment effect in the maturation of DCs and activation of T cells in melanoma-bearing mice model compared with PTT or CpG ODNs alone. Furthermore, in a tumor recurrence model, photothermal-immune combination therapy increased the infiltration of CTLs in distant tumor compared with PTT or CpG ODNs alone. The combination therapy overcame insufficient immunity at distant tumor caused by PTT alone and relieved immunosuppression microenvironment of the tumor. Hence, the PDA based core-shell nanoplatform presents a potent photo-immunotherapy against proliferation and recurrence of melanoma. STATEMENT OF SIGNIFICANCE: In order to solve the insufficient immunity induced by photothermal therapy (PTT), CpG ODNs were utilized to enhance the weak immune response mediated by PTT through inducing DCs maturation. Hence, we designed a polydopamine (PDA) based core-shell nanoplatform loading CpG ODNs followed by hyaluronic acid named PPP/CpG/HA to elicit robust photothermal ablation and antitumor immune responses. CpG ODNs were delivered to the tumor site through the targeting effect of the HA shell. The core-shell nanoplatform achieved a remarkable synergistic treatment effect in the maturation of DCs and activation of T cells, thereby overcoming insufficient immunity at distant tumor caused by PTT alone. The core-shell nanoplatform presents a potent photo-immunotherapy against proliferation and recurrence of melanoma.

Reeducating Tumor-Associated Macrophages Using CpG@Au Nanocomposites to Modulate Immunosuppressive Microenvironment for Improved Radio-Immunotherapy

With the recent success of immune checkpoint blockade (ICB) in cancer immunotherapy, there has been renewed interest in evaluating the combination of ICB inhibitors with radiotherapy (RT) in clinical trials in view of the localized RT-initiated vaccination effect, which can be augmented further by systemic immune-stimulating agents. Unfortunately, traditional RT/ICB accompanies severe toxicity from high-dose ionizing irradiation and low response rate from RT-aggravated immunosuppression, among which M2-type tumor-associated macrophages (TAMs) play an important role. Herein, CpG-decorated gold (Au) nanoparticles (CpG@Au NPs) were fabricated to improve the RT/ICB efficacy by immune modulation under low-dose X-ray exposure, where Au NPs served as radioenhancers to minimize the radiotoxicity, and yet acted as nanocarriers to deliver CpG, a toll-like receptor 9 agonist, to re-educate immunosuppressive M2 TAMs to immunostimulatory M1 counterparts, thus arousing innate immunity and meanwhile priming T cell activation. When combined with an anti-programmed death 1 antibody, irradiated CpG@Au led to consistent abscopal responses that efficiently suppressed distant tumors in a bilateral GL261 tumor-bearing model. This work thus demonstrates that CpG@Au-mediated macrophage reeducation could efficiently modulate the tumor-immune microenvironment for synergistic RT/ICB.

Nano-bio interfaces effect of two-dimensional nanomaterials and their applications in cancer immunotherapy

The field of two-dimensional (2D) nanomaterial-based cancer immunotherapy combines research from multiple subdisciplines of material science, nano-chemistry, in particular nano-biological interactions, immunology, and medicinal chemistry. Most importantly, the "biological identity" of nanomaterials governed by bio-molecular corona in terms of bimolecular types, relative abundance, and conformation at the nanomaterial surface is now believed to influence blood circulation time, bio-distribution, immune response, cellular uptake, and intracellular trafficking. A better understanding of nano-bio interactions can improve utilization of 2D nano-architectures for cancer immunotherapy and immunotheranostics, allowing them to be adapted or modified to treat other immune dysregulation syndromes including autoimmune diseases or inflammation, infection, tissue regeneration, and transplantation. The manuscript reviews the biological interactions and immunotherapeutic applications of 2D nanomaterials, including understanding their interactions with biological molecules of the immune system, summarizes and prospects the applications of 2D nanomaterials in cancer immunotherapy.

Recent Advances in 2D Material-Mediated Immuno-Combined Cancer Therapy

In the last years, cancer immunotherapy has started to attract a lot of attention, becoming one of the alternatives in the clinical treatment of cancer. Indeed, one of the advantages of immunotherapy is that both primary and distant tumors can be efficiently eradicated through a triggered immune response. Due to their large specific surface area and unique physicochemical properties, 2D materials have become popular in cancer immunotherapy, especially as efficient drug carriers. They have been also exploited as photothermal platforms, chemodynamic agents, and photosensitizers to further enhance the efficacy of the therapy. In this review, the focus is on the recent development of 2D materials as new tools to combine immunotherapy with chemotherapy, photothermal therapy, photodynamic therapy, chemodynamic therapy, radiotherapy, and radiodynamic therapy. These innovative synergistic approaches intend to go beyond the classical strategies based on a simple delivery function of immune modulators by nanomaterials. Furthermore, the effects of the 2D materials themselves and their surface properties (e.g., chemical modification and protein corona formation) on the induction of an immune response will be also discussed.

A Novel Cascade Nanoreactor Integrating Two-Dimensional Pd-Ru Nanozyme, Uricase and Red Blood Cell Membrane for Highly Efficient Hyperuricemia Treatment

Nanozyme-based cascade reaction has emerged as an effective strategy for disease treatment because of its high efficiency and low side effects. Herein, a new and highly active two-dimensional Pd-Ru nanozyme is prepared and then integrated with uricase and red blood cell (RBC) membrane to fabricate a tandem nanoreactor, Pd-Ru/Uricase@RBC, for hyperuricemia treatment. The designed Pd-Ru/Uricase@RBC nanoreactor displayed not only good stability against extreme pH, temperature and proteolytic degradation, but also long circulation half-life and excellent safety. The nanoreactor can effectively degrade UA by uricase to allantoin and H₂ O₂ and remove H₂ O₂ by using Pd-Ru nanosheets (NSs) with the catalase (CAT)-like activity. More importantly, the finally produced O₂ from H₂ O₂ decomposition can in turn facilitate the catalytic oxidation of UA, as the degradation of UA is an O₂ consumption process. By integrating the high-efficiency enzymatic activity, long circulation capability, and good biocompatibility, the designed Pd-Ru/Uricase@RBC can effectively and safely treat hyperuricemia without side effects. The study affords a new alternative for the exploration of clinical treatment of hyperuricemia.

CpG-Based Nanovaccines for Cancer Immunotherapy

Cancer has been a serious health hazard to the people all over the world with its high incidence and horrible mortality. In recent years, tumor vaccines in immunotherapy have become a hotspot in cancer therapy due to their many practical advantages and good therapeutic potentials. Among the various vaccines, nanovaccine utilized nanoparticles (NPs) as the carrier and/or adjuvant has presented significant therapeutic effect in cancer treatment. For tumor nanovaccines, unmethylated cytosine-phosphate-guanine oligodeoxynucleotide (CpG ODN) is a commonly used adjuvant. It has been reported that CpG ODN was the most effective immune stimulant among the currently known adjuvants. It could be recognized by toll-like receptor 9 (TLR9) to activate humoral and cellular immunity for preventing or treating cancer. In this review, the topic of CpG-based nanovaccines for cancer immunotherapy will be focused. The types and properties of different CpG will be introduced in detail first, and then some representative tumor nanovaccines will be reviewed according to the diverse loading modes of CpG, such as electrostatic adsorption, covalent bonding, hydrophilic and hydrophobic interaction, and DNA self-assembly, for summarizing the current progress of CpG-based tumor nanovaccines. Finally, the challenges and future perspectives will be discussed. It is hoped that this review will provide valuable references for the development of nanovaccines in cancer immunotherapy.

Near-Infrared Light Enhanced Peroxidase-Like Activity of PEGylated Palladium Nanozyme for Highly Efficient Biofilm Eradication

The overall eradication of biofilm-mode growing bacteria holds significant key to the answer of a series of infection-related health problems. However, the extracellular matrix of bacteria biofilms disables the traditional antimicrobials and, more unfortunately, hampers the development of the anti-infectious alternatives. Therefore, highly effective antimicrobial agents are an urgent need for biofilm-infection control. Herein, a PEGylated palladium nanozyme (Pd-PEG) with peroxidase (POD)-like activity for highly efficient biofilm infection control is reported. Pd-PEG also shows the intrinsic photothermal effect as well as near-infrared (NIR) light-enhanced POD-like activity in the acidic environment, thereby massively destroying the biofilm matrix and killing the adhering bacteria. Importantly, the antimicrobial mechanism of the synergistic treatment based on Pd-PEG+H₂O₂+NIR combination was disclosed. In vitro and in vivo results illustrated the designed Pd-PEG+H₂O₂ +NIR treatment reagent possessed outstanding antibacterial and biofilms elimination effects with negligible biotoxicity. This work hopefully facilitates the development of metal-based nanozymes in biofilm related infectious diseases.

Systemic administration of polymersomal oncolytic peptide LTX-315 combining with CpG adjuvant and anti-PD-1 antibody boosts immunotherapy of melanoma

Oncolytic peptide LTX-315 while showing clinical promise in treating solid tumors is limited to intratumoral administration, which is not applicable for inaccessible or metastatic tumors. The cationic and amphipathic nature of oncolytic peptides engenders formidable challenges to developing systems for their systemic delivery. Here, we describe cRGD-functionalized chimaeric polymersomes (cRGD-CPs) as a robust systemic delivery vehicle for LTX-315, which in combination with CpG adjuvant and anti-PD-1 boost immunotherapy of malignant B16F10 melanoma in mice. cRGD-CPs containing 14.9 wt% LTX-315 (cRGD-CPs-L) exhibited a size of 53 nm, excellent serum stability, and strong and selective killing of B16F10 cells (versus L929 fibroblasts) in vitro, which provoked similar immunogenic effects to free LTX-315 as revealed by release of danger-associated molecular pattern molecules. The systemic administration of cRGD-CPs-L gave a notable tumor accumulation of 4.8% ID/g and significant retardation of tumor growth. More interestingly, the treatment of B16F10 tumor-bearing mice was further boosted by co-administration of polymersomal CpG and anti-PD-1 antibody, in which two out of seven mice were cured as a result of strong immune response and long-term immune memory protection. The immunotherapeutic effect was evidenced by secretion of IL-6, IFN-γ and TNF-α, tumor infiltration of CD8⁺ CTLs and T_h, and induction of T_EM and T_CM in spleen. This study opens a new avenue to oncolytic peptides, which enables durable immunotherapy of tumors via systemic administration.

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.

Near-infrared inorganic nanomaterial-based nanosystems for photothermal therapy

The development of robust materials for treating diseases through non-invasive photothermal therapy (PTT) has attracted increasing attention in recent years. Among various types of nanomaterials, inorganic nanomaterials with strong absorption in the near-infrared (NIR) window can be employed as high-efficiency photothermal agents to treat cancer and bacterial infections. In addition, inorganic nanomaterials can be easily combined with other drugs or chemical reagents to construct multifunctional nanomaterials to cascade stimulation responses, enhance therapeutic effects, and perform precise medical treatments. In this review, focusing on the latest developments of inorganic nanomaterials in photothermal therapy, we firstly introduced the light-to-heat conversion mechanism of inorganic nanomaterials. Secondly, we summarized the application of common inorganic nanomaterials, such as metallic nanoparticles, transition metal oxide nanoparticles and two dimensional (2D) nanosheets. In addition, the strategy of developing multifunctional nano-platforms with excellent biocompatibility as well as good targeted capability was also expounded. Finally, challenges and new perspectives for designing effective inorganic nanomaterial-based nanosystems for photothermal assisted therapy were also discussed.

Development of CpG oligodeoxynucleotide TLR9 agonists in anti-cancer therapy

INTRODUCTION

Toll-like receptor-9(TLR9) can recognize the foreign unmethylated CpG DNA, and thus intrigue a strong Th1 response which plays a crucial role in the innate and adaptive immune responses. To date, CpG oligodeoxynucleotide (ODN)-based TLR9 agonists have undergone four generations. Each generations' breakthroughs in immune activation, safety profiles and pharmacokinetic properties were confirmed by both preclinical and clinical studies.

AREAS COVERED

We reviewed the development and major clinical trials of TLR9 agonists and summarized the optimization strategies of each generation. The applications, limitations and prospects of TLR9 agonists in cancer immunotherapy are also discussed.

EXPERT OPINION

Clinical trials of CpG ODN TLR9 agonists as a single agent demonstrated insufficient efficacy to reverse the immunosuppressive status of majority of patients with high tumor burden. Therefore, more efforts are now been carried out in combination with chemotherapy, radiotherapy and immunotherapy maintenance therapy as well as vaccine adjuvant. Importantly, the synergistic and complementary effect of TLR9 agonists and tumor immune checkpoint inhibitor therapy is expected to exert greater potential. On the other hand, the double-edged sword effect of TLR9 activation in tumor and toxic effect reported in combination therapies should be noted and further studies required.

The synergistic strategies for the immuno-oncotherapy with photothermal nanoagents

Immuno-oncotherapy has shown great promise for the cure of late-stage and metastatic cancer. Great efforts have tried to improve the overall response rate (ORR) and to reduce the immune-related adverse events (irAEs). Antigen presentation, T cell activation and killing are interlocking and distinct steps to initiate effective anti-tumor immune responses. Aiming to overcome the tumor immune evasion whose mechanisms include limited release of neoantigen, suppressed infiltration of antigen-presenting cells (APCs) and T cells, and the expression of immune checkpoints (ICPs), combinational therapeutic strategies have shown great potential by activating the anti-tumor immune responses together with deactivating immunosuppressive conditions simultaneously. In this direction, photothermal therapy (PTT) has attracted attention due to the efficient ablation of tumor cells, of which the released immunogenic tumor debris can activate host immune responses. The combination of immunoadjuvants and/or ICP inhibitors can boost the anti-tumor immune responses, realizing PTT-synergized immuno-oncotherapy. In this regard, numerous multifunctional nanomaterials have been designed with integration of photothermal and immuno-oncotherapeutic agents into one package via well-designed surface modification and functionalization. This review summarizes the recent studies on the synergistic strategies for the immuno-oncotherapy based on photothermal nanoagents and the mechanisms that trigger the systemic anti-tumor immune responses and PTT-synergized immuno-oncotherapy. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Noble Metal Nanomaterials for NIR-Triggered Photothermal Therapy in Cancer

It is of great significance to develop anticancer therapeutic agents or technologies with high degree of specificity and patient compliance, while low toxicity. The emerging photothermal therapy (PTT) has become a new and powerful therapeutic technology due to its noninvasiveness, high specificity, low side effects to normal tissues and strong anticancer efficacy. Noble metal nanomaterials possess strong surface plasmon resonance (SPR) effect and synthetic tunability, which make them facile and effective PTT agents with superior optical and photothermal characteristics, such as high absorption cross-section, incomparable optical-thermal conversion efficiency in the near infrared (NIR) region, as well as the potential of bioimaging. By incorporating with various functional reagents such as antibodies, peptides, biocompatible polymers, chemo-drug and immune factors, noble metal nanomaterials have presented strong potential in multifunctional cancer therapy. Herein, the recent development regarding the application of noble metal nanomaterials for NIR-triggered PTT in cancer treatment is summarized. A variety of studies with good therapeutic effects against cancer from impressive photothermal efficacy of noble metal nanomaterials are concluded. Intelligent nanoplatforms through ingenious fabrication showing potential of multifunctional PTT, combined with chemo-therapy, immunotherapy, photodynamic therapy (PDT), as well as simultaneous imaging modality are also demonstrated.

Recent Advances in Hyperthermia Therapy-Based Synergistic Immunotherapy

The past decades have witnessed hyperthermia therapy (HTT) as an emerging strategy against malignant tumors. Nanomaterial-based photothermal therapy (PTT) and magnetic hyperthermia (MHT), as highly effective and noninvasive treatment models, offer advantages over other strategies in the treatment of different types of tumors. However, both PTT and MHT cannot completely cure cancer due to recurrence and distal metastasis. In recent years, cancer immunotherapy has attracted widespread attention owing to its capability to activate the body's own natural defense to identify, attack, and eradicate cancer cells. Significant efforts have been devoted to studying the activated immune responses caused by hyperthermia-ablated tumors. In this article, the synergistic mechanism of HTT in immunotherapy, including immunogenic cell death and reversal of the immunosuppressive tumor microenvironment is discussed. The reports of the combination of HTT or HTT-based multimodal therapy with immunotherapy, including immunoadjuvant exploitation, immune checkpoint blockade therapy, and adoptive cellular immunotherapy are summarized. As highlighted, these strategies could achieve synergistically enhanced therapeutic outcomes against both primary tumors and metastatic lesions, prevent cancer recurrence, and prolong the survival period. Finally, current challenges and prospective developments in HTT-synergized immunotherapy are also reviewed.

Biomimetic Anti-PD-1 Peptide-Loaded 2D FePSe3 Nanosheets for Efficient Photothermal and Enhanced Immune Therapy with Multimodal MR/PA/Thermal Imaging

Metal phosphorous trichalcogenides (MPX3) are novel 2D nanomaterials that have recently been exploited as efficient photothermal-chemodynamic agents for cancer therapy. As a representative MPX3, FePSe3 has the potential to be developed as magnetic resonance imaging (MRI) and photoacoustic imaging (PAI) agents due to the composition of Fe and the previously revealed PA signal. Here, a FePSe3-based theranostic agent, FePSe3@APP@CCM, loaded with anti-PD-1 peptide (APP) as the inner component and CT26 cancer cell membrane (CCM) as the outer shell is reported, which acts as a multifunctional agent for MR and PA imaging and photothermal and immunotherapy against cancer. FePSe3@APP@CCM induces highly efficient tumor ablation and suppresses tumor growth by photothermal therapy under near-infrared laser excitation, which further activates immune responses. Moreover, APP blocks the PD-1/PD-L1 pathway to activate cytotoxic T cells, causing strong anticancer immunity. The combined therapy significantly prolongs the lifespan of experimental mice. The multimodal imaging and synergistic therapeutic effects of PTT and its triggered immune responses and APP-related immunotherapy are clearly demonstrated by in vitro and in vivo experiments. This work demonstrates the potential of MPX3-based biomaterials as novel theranostic agents.

Nanoparticle Phototherapy in the Era of Cancer Immunotherapy

Phototherapy, including photodynamic therapy and photothermal therapy, exploits light to activate photo-reactions that kill cancer cells. Recent studies show that phototherapy can not only kill irradiated tumor cells, but also elicit a tumor specific immune response. This phenomenon breaks the limitations of conventional phototherapy, and has reinvigorated phototherapy-related research in the era of cancer immunotherapy. Nanoparticles play essential roles in this new campaign for allowing simultaneous delivery of photo-reactive agents and immune modulators. Some nanoparticles are potent adjuvants on their own and can augment anticancer immunity to fight off tumor relapse and metastasis. In this review, we summarize recent advances on exploiting nanoparticle-based photodynamic therapy and photothermal therapy for cancer immunotherapy, with an emphasis on nanoplatform design and functions.

Pd@Pt-GOx/HA as a Novel Enzymatic Cascade Nanoreactor for High-Efficiency Starving-Enhanced Chemodynamic Cancer Therapy

Glucose oxidase (GOx)-mediated starvation therapy has demonstrated good application prospect in cancer treatment. However, the glucose- and oxygen-depletion starvation therapy still suffers from some limitations like low therapeutic efficiency and potential side effects to normal tissues. To overcome these disadvantages, herein a novel enzymatic cascade nanoreactor (Pd@Pt-GOx/hyaluronic acid (HA)) with controllable enzymatic activities was developed for high-efficiency starving-enhanced chemodynamic cancer therapy. The Pd@Pt-GOx/HA was fabricated by covalent conjugation of GOx onto Pd@Pt nanosheets (NSs), followed by linkage with hyaluronic acid (HA). The modification of HA on Pd@Pt-GOx could block the GOx activity, catalase (CAT)-like and peroxidase (POD)-like activities of Pd@Pt, reduce the cytotoxicity to normal cells and organs, and effectively target CD44-overexpressed tumors by active targeting and passive enhanced permeability and retention (EPR) effect. After endocytosis by tumor cells, the intracellular hyaluronidase (Hyase) could decompose the outer HA and expose Pd@Pt-GOx for the enzymatic cascade reaction. The GOx on the Pd@Pt-GOx could catalyze the oxidation of intratumoral glucose by O₂ for cancer starvation therapy, while the O₂ produced from the decomposition of endogenous H₂O₂ by the Pd@Pt with the CAT-like activity could accelerate the O₂-dependent depletion of glucose by GOx. Meanwhile, the upregulated acidity and H₂O₂ content in the tumor region generated by GOx catalytic oxidation of glucose dramatically facilitated the pH-responsive POD-like activity of the Pd@Pt nanozyme, which then catalyzed degradation of the H₂O₂ to generate abundant highly toxic ^•OH, thereby realizing nanozyme-mediated starving-enhanced chemodynamic cancer therapy. In vitro and in vivo results indicated that the controllable, self-activated enzymatic cascade nanoreactors exerted highly efficient anticancer effects with negligible biotoxicity.

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.

Reprogramming Tumor Microenvironment with Photothermal Therapy

The tumor microenvironment significantly influences cancer progression and therapeutic response. Reprogramming of tumor microenvironment has emerged as a strategy to assist conventional cancer treatment. In recent years, photothermal therapy has received considerable attention owing to its noninvasiveness, high temporal-spatial resolution, and minimal drug resistance. Apart from ablating cancer cells by generating heat upon light irradiation, photothermal therapy can also affect the tumor microenvironment, such as disrupting the tumor extracellular matrix and tumor vasculature. Moreover, cancer cell death by hyperthermia could potentially activate the immune system to fight against tumor. In this topical review, we focus on the recent progress of photothermal therapy based on tumor microenvironment remodeling, aiming to better guide the design of nanoparticles for cancer photoimmunotherapy.