Mechanical Immunoengineering of T cells for Therapeutic Applications.

T cells, a key component in adaptive immunity, are central to many immunotherapeutic modalities aimed at treating various diseases including cancer, infectious diseases, and autoimmune disorders. The past decade has witnessed tremendous progress in immunotherapy, which aims at activation or suppression of the immune responses for disease treatments. Most strikingly, cancer immunotherapy has led to curative responses in a fraction of patients with relapsed or refractory cancers. However, extending those clinical benefits to a majority of cancer patients remains challenging. In order to improve both efficacy and safety of T cell-based immunotherapies, significant effort has been devoted to modulating biochemical signals to enhance T cell proliferation, effector functions, and longevity. Such strategies include discovery of new immune checkpoints, design of armored chimeric antigen receptor (CAR) T cells, and targeted delivery of stimulatory cytokines and so on.Despite the intense global research effort in developing novel cancer immunotherapies, a major dimension of the interactions between cancer and the immune system, its biomechanical aspect, has been largely underappreciated. Throughout their lifecycle, T cells constantly survey a multitude of organs and tissues and experience diverse biomechanical environments, such as shear force in the blood flow and a broad range of tissue stiffness. Furthermore, biomechanical properties of tissues or cells may be altered in disease and inflammation. Biomechanical cues, including both passive mechanical cues and active mechanical forces, have been shown to govern T cell development, activation, migration, differentiation, and effector functions. In other words, T cells can sense, respond to, and adapt to both passive mechanical cues and active mechanical forces.Biomechanical cues have been intensively studied at a fundamental level but are yet to be extensively incorporated in the design of immunotherapies. Nonetheless, the growing knowledge of T cell mechanobiology has formed the basis for the development of novel engineering strategies to mechanically modulate T cell immunity, a nascent field that we termed "mechanical immunoengineering". Mechanical immunoengineering exploits biomechanical cues (e.g., stiffness and external forces) to modulate T cell differentiation, proliferation, effector functions, etc., for diagnostic or therapeutic applications. It provides an additional dimension, complementary to traditional modulation of biochemical cues (e.g., antigen density and co-stimulatory signals), to tailor T cell immune responses and enhance therapeutic outcomes. For example, stiff antigen-presenting matrices have been shown to enhance T cell proliferation independently of the intensity of biochemical stimulatory signals. Current strategies of mechanical immunoengineering of T cells can be categorized into two major fields including passive mechanical cue-oriented and active force-oriented strategies. In this Account, we first present a brief overview of T cell mechanobiology. Next, we summarize recent advances in mechanical immunoengineering, discuss the roles of chemistry and material science in the development of these engineering strategies, and highlight potential therapeutic applications. Finally, we present our perspective on the future directions in mechanical immunoengineering and critical steps to translate mechanical immunoengineering strategies into therapeutic applications in the clinic.

Cancer-cell stiffening via cholesterol depletion enhances adoptive T-cell immunotherapy.

Malignant transformation and tumour progression are associated with cancer-cell softening. Yet how the biomechanics of cancer cells affects T-cell-mediated cytotoxicity and thus the outcomes of adoptive T-cell immunotherapies is unknown. Here we show that T-cell-mediated cancer-cell killing is hampered for cortically soft cancer cells, which have plasma membranes enriched in cholesterol, and that cancer-cell stiffening via cholesterol depletion augments T-cell cytotoxicity and enhances the efficacy of adoptive T-cell therapy against solid tumours in mice. We also show that the enhanced cytotoxicity against stiffened cancer cells is mediated by augmented T-cell forces arising from an increased accumulation of filamentous actin at the immunological synapse, and that cancer-cell stiffening has negligible influence on: T-cell-receptor signalling, production of cytolytic proteins such as granzyme B, secretion of interferon gamma and tumour necrosis factor alpha, and Fas-receptor-Fas-ligand interactions. Our findings reveal a mechanical immune checkpoint that could be targeted therapeutically to improve the effectiveness of cancer immunotherapies.

Surgery-free injectable macroscale biomaterials for local cancer immunotherapy.

Immunotherapy can harness the power of host's immune system to fight cancer. In the last few decades, tremendous progress has been made in this field, with remarkable clinical successes achieved consisting of a durable response in a fraction of patients. However, there are enormous challenges to extending this therapy to the majority of cancer patients while retaining minimal adverse effects. Local immunotherapy is a promising approach for concentrating immunomodulation in situ without systemic exposure, therefore minimizing systemic toxicities. More importantly, local immunomodulation can still lead to systemic effects that confer overall anticancer immunity to eradicate disseminated diseases. To facilitate these local immunotherapies, a wide range of biomaterials have been developed as delivery systems to protect the locally injected immune-related therapeutics and extend their retention. Surgery-free injectable macroscale biomaterials are one of the most promising classes of biomaterials developed to date, as they are suitable for minimally invasive injection with needles or catheters and form a biocompatible three-dimensional matrix in situ as a drug-depot for controlled local delivery. In this mini-review, we provide an overview of the recent advancements in applying injectable macroscale biomaterials in local cancer immunotherapy by highlighting some recent examples. We compare various injectable biomaterials with different gelation mechanisms and discuss their applications in the delivery of immunomodulators, immune cells, and cancer vaccines. We also discuss current challenges and provide a perspective for the future development of injectable macroscale biomaterials in cancer immunotherapy.

Injectable PEG/polyester thermogel: A new liquid embolization agent for temporary vascular interventional therapy.

Injectable poly(ethylene glycol) (PEG)/polyester thermogels exhibit superior injectability and unique thermoreversible sol-gel transitions compared with Onyx™, which is the only liquid embolic agent approved by the U.S. Food and Drug Administration. Herein, the feasibility of an injectable methoxy PEG-poly(d,l-lactide) copolymer (mPEG-PLA) thermogel for temporary vascular interventional therapy was evaluated in the large animal (swine) model for the first time. This mPEG-PLA polymer was soluble in water at a low temperature and exhibited a reversible sol-gel transition with increasing temperature. Meanwhile, the addition of an X-ray contrast agent did not significantly affect the gelation behavior of the thermogel but did confer excellent radiopacity, allowing intraoperative X-ray imaging guidance. In vivo experiments demonstrated that compared with traditional embolic agents, the mPEG-PLA thermogel required less preparation time and could be injected more conveniently during the operation. The temporary arterial embolization was achieved after the thermogel injection, yet the blocked arteries were recanalized 1 hour post-operation. Consequently, the mPEG-PLA thermogel shows some potential as a temporary pre-surgical embolic agent for tumor resection, but further researches including enhancing mechanical strength of gel are required to improve the embolization efficacy of PEG/polyester thermogel in the future.

Neoantigen Vaccine Delivery for Personalized Anticancer Immunotherapy.

Cancer neoantigens derived from random somatic mutations in tumor tissue represent an attractive type of targets for the cancer immunotherapies including cancer vaccine. Vaccination against the tumor-specific neoantigens minimizes the potential induction of central and peripheral tolerance as well as the risk of autoimmunity. Neoantigen-based cancer vaccines have recently showed marked therapeutic potential in both preclinical and early-phase clinical studies. However, significant challenges remain in the effective and faithful identification of immunogenic neoepitopes and the efficient and safe delivery of the subunit vaccine components for eliciting potent and robust anticancer T cell responses. In this mini review, we provide a brief overview of the recent advances in the development of neoantigen-based cancer vaccines focusing on various vaccine delivery strategies for targeting and modulating antigen-presenting cells. We discuss current delivery approaches, including direct injection, ex vivo-pulsed dendritic cell vaccination, and biomaterial-assisted vaccination for enhancing the efficiency of neoantigen vaccines and present a perspective on future directions.

Non-invasive monitoring of in vivo degradation of a radiopaque thermoreversible hydrogel and its efficacy in preventing post-operative adhesions.

In vivo behavior of hydrogel-based biomaterials is very important for rational design of hydrogels for various biomedical applications. Herein, we developed a facile method for in situ fabrication of radiopaque hydrogel. An iodinated functional diblock copolymer of poly(ethylene glycol) and aliphatic polyester was first synthesized by coupling the hydroxyl end of the diblock copolymer with 2,3,5-triiodobenzoic acid (TIB) and then a radiopaque thermoreversible hydrogel was obtained by mixing it with the virgin diblock copolymer. A concentrated aqueous solution of the copolymer blend was injectable at room temperature and spontaneously turned into an in situ hydrogel at body temperature after injection. The introduction of TIB moieties affords the capacity of X-ray opacity, enabling in vivo visualization of the hydrogel using Micro-CT. A rat model with cecum and abdominal defects was utilized to evaluate the efficacy of the radiopaque hydrogel in the prevention of post-operative adhesions, and a significant reduction of the post-operative adhesion formation was confirmed. Meanwhile, the maintenance of the radiopaque hydrogel in the abdomen after administration was non-destructively detected via Micro-CT scanning. The reconstructed three-dimensional images showed that the radiopaque hydrogel with an irregular morphology was located on the injured abdominal wall. The time-dependent profile of the volume of the radiopaque hydrogel determined by Micro-CT imaging was well consistent with the trend obtained from the dissection observation. Therefore, the radiopaque thermoreversible hydrogel can serve as a potential visualized biomedical implant and this practical mixing approach is also useful for further extension into the in vivo monitoring of other biomaterials. STATEMENT OF SIGNIFICANCE: While a variety of biomaterials have been extensively studied, it is rare to monitor in vivo degradation and medical efficacy of a material after being implanted deeply into the body. Herein, the radiopaque thermoreversible hydrogel developed by us not only holds desirable performance on the prevention of post-operative abdominal adhesions, but also allows non-invasive monitoring of its in vivo degradation with CT imaging in a real-time, quantitative and three-dimensional manner. The methodology based on CT imaging provides important insights into the in vivo fate of the hydrogel after being deeply implanted into mammals for different biomedical applications and significantly reduces the amount of animals sacrificed.

Functional biomedical hydrogels for in vivo imaging.

Hydrogels have gained tremendous attention owing to their great potential in biomedical applications such as tissue engineering and drug delivery. Their in vivo fate like in vivo degradation serves as a crucial factor in achieving the desired efficacy. Traditional anatomic observation has been used to investigate the in vivo degradation of hydrogels; however, invasive assessment at each time point significantly increases the number of animals needed for each experiment and is not able to monitor the same formulation throughout the whole period. In recent years, hydrogels functionalized with contrast agents have emerged as a non-invasive tool for long term in vivo tracking of the degradation patterns of hydrogel systems, enabling spatial and temporal visualization of the status of structure (morphology, volume, porosity, etc.) and function (cell distribution, foreign response, etc.) of implanted hydrogels. In this review, current mainstreams of functional imaging hydrogels for in vivo tracking and their synthetic strategies are summarized and discussed. The future of functional imaging hydrogels is also envisioned based on the recent advances in imaging techniques.

Injectable and Thermosensitive Hydrogel Containing Liraglutide as a Long-Acting Antidiabetic System.

Diabetes, a global epidemic, has become a serious threat to public health. The present study is aimed at constructing an injectable thermosensitive PEG-polyester hydrogel formulation of liraglutide (Lira), a "smart" antidiabetic polypeptide, in the long-acting treatment of type 2 diabetes mellitus. A total of three thermosensitive poly(ε-caprolactone-co-glycolic acid)-poly(ethylene glycol)-poly(ε-caprolactone-co-glycolic acid) (PCGA-PEG-PCGA) triblock copolymers with similar molecular weights but different ε-caprolactone-to-glycolide (CL-to-GA) ratios were synthesized. The polymer aqueous solutions exhibited free-flowing sols at room temperature and formed in situ hydrogels at body temperature. While the different bulk morphologies, stabilities of aqueous solutions, and the varying in vivo persistence time of hydrogels in ICR mice were found among the three copolymers, all of the Lira-loaded gel formulations exhibited a sustained drug release manner in vitro regardless of CL-to-GA ratios. The specimen with a powder form in the bulk state, a stable aqueous solution before heating, and an appropriate degradation rate in vivo was selected as the optimal carrier to evaluate the in vivo efficacy. A single injection of the optimal gel formulation showed a remarkable hypoglycemic efficacy up to 1 week in diabetic db/db mice. Furthermore, three successive administrations of this gel formulation within one month significantly lowered glycosylated hemoglobin and protected islets of db/db mice. As a result, a promising once-weekly delivery system of Lira was developed, which not only afforded long-term glycemic control but also significantly improved patient compliance.

An injectable thermogel with high radiopacity.

An injectable PEG/polyester thermogel with strong X-ray opacity was designed and synthesized through the conjugation of 2,3,5-triiodobenzoic acid to the hydrophobic end of the mPEG-PLA diblock copolymer for the first time.