DH5α Outer Membrane-Coated Biomimetic Nanocapsules Deliver Drugs to Brain Metastases but not Normal Brain Cells via Targeting GRP94

Recent advances in biomimetic strategies for the immunotherapy of glioblastoma

Immunotherapy is regarded as one of the most promising approaches for treating tumors, with a multitude of immunotherapeutic thoughts currently under consideration for the lethal glioblastoma (GBM). However, issues with immunotherapeutic agents, such as limited in vivo stability, poor blood-brain barrier (BBB) penetration, insufficient GBM targeting, and represented monotherapy, have hindered the success of immunotherapeutic interventions. Moreover, even with the aid of conventional drug delivery systems, outcomes remain suboptimal. Biomimetic strategies seek to overcome these formidable drug delivery challenges by emulating nature's intelligent structures and functions. Leveraging the variety of biological structures and functions, biomimetic drug delivery systems afford a versatile platform with enhanced biocompatibility for the co-delivery of diverse immunotherapeutic agents. Moreover, their inherent capacity to traverse the BBB and home in on GBM holds promise for augmenting the efficacy of GBM immunotherapy. Thus, this review begins by revisiting the various thoughts and agents on immunotherapy for GBM. Then, the barriers to successful GBM immunotherapy are analyzed, and the corresponding biomimetic strategies are explored from the perspective of function and structure. Finally, the clinical translation's current state and prospects of biomimetic strategy are addressed. This review aspires to provide fresh perspectives on the advancement of immunotherapy for GBM.

Brain-tumor-seeking and serpin-inhibiting outer membrane vesicles restore plasmin-mediated attacks against brain metastases

Many chemotherapeutic and molecular targeted drugs have been used to treat brain metastases, e.g., anti-angiogenic vandetanib. However, the blood-brain barrier and brain-specific resistance mechanisms make these systemic therapeutic approaches inefficacious. Brain metastatic cancer cells could mimic neurons to upregulate multiple serpins and secrete them into the extracellular environment to reduce local plasmin production to promote L1CAM-mediated vessel co-option and resist anti-angiogenesis therapy. Here, we developed brain-tumor-seeking and serpin-inhibiting outer membrane vesicles (DE@OMVs) to traverse across the blood-brain barrier, bypass neurons, and specially enter metastatic cancer cells via targeting GRP94 and vimentin. Through specific delivery of dexamethasone and embelin, reduced serpin secretion, restored plasmin production, significant L1CAM inactivation and tumor cell apoptosis were specially found in intracranial metastatic regions, leading to delayed tumor growth and prolonged survival in mice with brain metastases. By combining the brain-tumor-seeking properties with the regulation of the serpin/plasminogen activator/plasmin/L1CAM axis, this study provides a potent and highly-selective systemic therapeutic option for brain metastases.

Boosting Checkpoint Immunotherapy with Biomimetic Nanodrug Delivery Systems

Immune checkpoint blockade (ICB) has achieved unprecedented progress in tumor immunotherapy by blocking specific immune checkpoint molecules. However, the high biodistribution of the drug prevents it from specifically targeting tumor tissues, leading to immune-related adverse events. Biomimetic nanodrug delivery systems (BNDSs) readily applicable to ICB therapy have been widely developed at the preclinical stage to avoid immune-related adverse events. By exploiting or mimicking complex biological structures, the constructed BNDS as a novel drug delivery system has good biocompatibility and certain tumor-targeting properties. Herein, the latest findings regarding the aforementioned therapies associated with ICB therapy are highlighted. Simultaneously, prospective bioinspired engineering strategies can be designed to overcome the four-level barriers to drug entry into lesion sites. In future clinical translation, BNDS-based ICB combination therapy represents a promising avenue for cancer treatment.

The Role of Bacteria in Central Nervous System Tumors: Opportunities and Challenges

Tumors of the central nervous system (CNS) are severe and refractory diseases with poor prognosis, especially for patients with malignant glioblastoma and brain metastases. Currently, numerous studies have explored the potential role of bacteria and intestinal flora in tumor development and treatment. Bacteria can penetrate the blood-brain barrier (BBB), targeting the hypoxic microenvironment at the core of tumors, thereby eliminating tumors and activating both the innate and adaptive immune responses, rendering them promising therapeutic agents for CNS tumors. In addition, engineered bacteria and derivatives, such as bacterial membrane proteins and bacterial spores, can also be used as good candidate carriers for targeted drug delivery. Moreover, the intestinal flora can regulate CNS tumor metabolism and influence the immune microenvironment through the "gut-brain axis". Therefore, bacterial anti-tumor therapy, engineered bacterial targeted drug delivery, and intervention of the intestinal flora provide therapeutic modalities for the treatment of CNS tumors. In this paper, we performed a comprehensive review of the mechanisms and therapeutic practices of bacterial therapy for CNS tumors and discussed potential future research directions in this field.

Combining Multifunctional Delivery System with Blood-Brain Barrier Reversible Opening Strategy for the Enhanced Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative illness characterized by intracellular tau-phosphorylation, β-amyloid (Aβ) plaques accumulation, neuroinflammation, and impaired behavioral ability. Owing to the lack of effective brain delivery approaches and the presence of the blood-brain barrier (BBB), current AD therapeutic endeavors are severely limited. Herein, a multifunctional delivery system (RVG-DDQ/PDP@siBACE1) is elaborately combined with a protein kinase B (AKT) agonist (SC79) for facilitating RVG-DDQ/PDP@siBACE1 to target and penetrate BBB, enter brain parenchyma, and further accumulate in AD brain lesion. Moreover, compared with the unitary dose of RVG-DDQ/PDP@siBACE1, this collaborative therapy strategy exhibits a distinctive synergistic function including scavenging reactive oxygen species (ROS), decreasing of Aβ production, alleviating neuroinflammation by promoting the polarized microglia into the anti-inflammatory M2-like phenotype and significantly enhancing the cognitive functions of AD mice. More strikingly, according to these results, an innovative signaling pathway "lncRNA MALAT1/miR-181c/BCL2L11" is found that can mediate the neuronal apoptosis of AD. Taken together, combining the brain targeted delivery system with noninvasive BBB opening can provide a promising strategy and platform for targeting treatment of AD and other neurodegenerative diseases.

Engineered bacterial extracellular vesicles for central nervous system diseases

The prevalence of central nervous system (CNS) diseases is on the rise as the population ages. The presence of various obstacles, particularly the blood-brain barrier (BBB), poses a challenge for drug delivery to the CNS. An expanding body of study suggests that gut microbiota (GM) plays an important role in CNS diseases. The communication between GM and CNS diseases has received increasing attention. Accumulating evidence indicates that the GM can modulate host signaling pathways to regulate distant organ functions by delivering bioactive substances to host cells via bacterial extracellular vesicles (BEVs). BEVs have emerged as a promising platform for the treatment of CNS diseases due to their nanostructure, ability to penetrate the BBB, as well as their low toxicity, high biocompatibility, ease of modification and large-scale culture. Here, we discuss the biogenesis, internalization mechanism and engineering modification methods of BEVs. We then focus on the use and potential role of BEVs in the treatment of CNS diseases. Finally, we outline the main challenges and future prospects for the application of BEVs in CNS diseases. We hope that the comprehensive understanding of the BEVs-based gut-brain axis will provide new insights into the treatment of CNS diseases.