Immune Checkpoint Reprogramming via Sequential Nucleic Acid Delivery Strategy Optimizes Systemic Immune Responses for Gastrointestinal Cancer Immunotherapy

Monoclonal antibodies targeting immune checkpoints have been widely applied in gastrointestinal cancer immunotherapy. However, systemic administration of various monoclonal antibodies does not often result in sustained effects in reversing the immunosuppressive tumor microenvironment (TME), which may be due to the spatiotemporal dynamic changes of immune checkpoints. Herein, we reported a novel immune checkpoint reprogramming strategy for gastrointestinal cancer immunotherapy. It was achieved by the sequential delivery of siPD-L1 (siRNA for programmed cell death ligand 1) and pOX40L (plasmid for OX40 ligand), which were complexed with two cationic polymer brush-grafted carbon nanotubes (dense short (DS) and dense long (DL)) designed based on the structural characteristics of nucleic acids and brush architectures. Upon administrating DL/pOX40L for the first three dosages, then followed by DS/siPD-L1 for the next three dosages to the TME, it upregulated the stimulatory checkpoint OX40L on dendritic cells (DCs) and downregulated inhibitory checkpoint PD-L1 on tumor cells and DCs in a sequential reprogramming manner. Compared with other combination treatments, this sequential strategy drastically boosted the DCs maturation, and CD8+ cytotoxic T lymphocytes infiltration in tumor site. Furthermore, it could augment the local antitumor response and improve the T cell infiltration in tumor-draining lymph nodes to reverse the peripheral immunosuppression. Our study demonstrated that sequential nucleic acid delivery strategy via personalized nanoplatforms effectively reversed the immunosuppression status in both tumor microenvironment and peripheral immune landscape, which significantly enhanced the systemic antitumor immune responses and established an optimal immunotherapy strategy against gastrointestinal cancer.

The impact of pericytes on the stability of microvascular networks in response to nanoparticles

Recapitulating the normal physiology of the microvasculature is pivotal in the development of more complex in-vitro models and organ-on-chip designs. Pericytes are an important component of the vasculature, promoting vessel stability, inhibiting vascular permeability and maintaining the vascular hierarchical architecture. The use of such co-culture for the testing of therapeutics and nanoparticle safety is increasingly considered for the validation of therapeutic strategies. This report presents the use of a microfluidic model for such applications. Interactions between endothelial cells and pericytes are first explored. We identify basal conditions required to form stable and reproducible endothelial networks. We then investigate interactions between endothelial cells and pericytes via direct co-culture. In our system, pericytes prevented vessel hyperplasia and maintained vessel length in prolonged culture (> 10 days). In addition, these vessels displayed barrier function and expression of junction markers associated with vessel maturation, including VE-cadherin, β-catenin and ZO-1. Furthermore, pericytes maintained vessel integrity following stress (nutrient starvation) and prevented vessel regression, in contrast to the striking dissociation of networks in endothelial monocultures. This response was also observed when endothelial/pericyte co-cultures were exposed to high concentrations of moderately toxic cationic nanoparticles used for gene delivery. This study highlights the importance of pericytes in protecting vascular networks from stress and external agents and their importance to the design of advanced in-vitro models, including for the testing of nanotoxicity, to better recapitulate physiological response and avoid false positives.

Advances in design of polymer brush functionalized inorganic nanomaterials and their applications in biomedical arena

Grafting of polymer brush (assembly of polymer chains tethered to the substrate by one end) is emerging as one of the most viable approach to alter the surface of inorganic nanomaterials. Inorganic nanomaterials despite their intrinsic functional superiority, their applications remain restricted due to their incompatibility with organic or biological moieties vis-à-vis agglomeration issues. To overcome such a shortcoming, polymer brush modified surfaces of inorganic nanomaterials have lately proved to be of immense potential. For example, polymer brush-modified inorganic nanomaterials can act as efficient substrates/platforms in biomedical applications, ranging from drug-delivery to protein-array due to their integrated advantages such as amphiphilicity, stimuli responsiveness, enhanced biocompatibility, and so on. In this review, the current state of the art related to polymer brush-modified inorganic nanomaterials focusing, not only, on their synthetic strategies and applications in biomedical field but also the architectural influence of polymer brushes on the responsiveness properties of modified nanomaterials have comprehensively been discussed and its associated future perspective is also presented. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Synthetic strategies to enhance the long-term stability of polymer brush coatings

High-density, end-anchored macromolecules that form so-called polymer brushes are popular components of bio-inspired surface coatings. In a bio-memetic approach, they have been utilized to reduce friction, repel contamination and control...

Competitive binding and molecular crowding regulate the cytoplasmic interactome of non-viral polymeric gene delivery vectors

In contrast to the processes controlling the complexation, targeting and uptake of polycationic gene delivery vectors, the molecular mechanisms regulating their cytoplasmic dissociation remains poorly understood. Upon cytosolic entry, vectors become exposed to a complex, concentrated mixture of molecules and biomacromolecules. In this report, we characterise the cytoplasmic interactome associated with polycationic vectors based on poly(dimethylaminoethyl methacrylate) (PDMAEMA) and poly(2-methacrylolyloxyethyltrimethylammonium chloride) (PMETAC) brushes. To quantify the contribution of different classes of low molar mass molecules and biomacromolecules to RNA release, we develop a kinetics model based on competitive binding. Our results identify the importance of competition from highly charged biomacromolecules, such as cytosolic RNA, as a primary regulator of RNA release. Importantly, our data indicate the presence of ribosome associated proteins, proteins associated with translation and transcription factors that may underly a broader impact of polycationic vectors on translation. In addition, we bring evidence that molecular crowding modulates competitive binding and demonstrate how the modulation of such interactions, for example via quaternisation or the design of charge-shifting moieties, impacts on the long-term transfection efficiency of polycationic vectors. Understanding the mechanism regulating cytosolic dissociation will enable the improved design of cationic vectors for long term gene release and therapeutic efficacy.

Factors controlling release of loaded cargo from polycationic gene delivery vectors are still poorly understood. Here, the authors report on a study of mechanisms of RNA release, highlighting the role of competitive binding, and characterise the interactome associated with vectors upon cytosolic entry.

Brush-like polymers: design, synthesis and applications

With the development of controlled polymerisation, almost all polymerisation strategies have been successfully transplanted to surface-initiated polymerisation. The resulting polymer brushes have emerged as an effective tool for surface functionalization and modulation of the surface properties of materials. To meet various demands it is possible to tailor a material surface with polymer brushes that have diverse dimensionalities, morphologies and compositions. The crowded environment within polymer brushes as well as the stretched conformation of polymer chains sometimes provide unique physicochemical properties, which lead to the delicate creation of inorganic-organic hybridised nanostructures, anti-fouling coatings, biomedical carriers, and materials for use in lubrication, photonics and energy storage. So far, challenges remain in the high-precision synthesis and topological control needed to realize extended applications of polymer brushes. In this Feature Article, we highlight the topology, potential application prospects and various synthetic protocols, particularly for recently established methods, for the efficient synthesis of polymer brushes, as well as their benefits and limitations.

Nanotechnology-Assisted RNA Delivery: From Nucleic Acid Therapeutics to COVID-19 Vaccines

In recent years, the main quest of science has been the pioneering of the groundbreaking biomedical strategies needed for achieving a personalized medicine. Ribonucleic acids (RNAs) are outstanding bioactive macromolecules identified as pivotal actors in regulating a wide range of biochemical pathways. The ability to intimately control the cell fate and tissue activities makes RNA-based drugs the most fascinating family of bioactive agents. However, achieving a widespread application of RNA therapeutics in humans is still a challenging feat, due to both the instability of naked RNA and the presence of biological barriers aimed at hindering the entrance of RNA into cells. Recently, material scientists' enormous efforts have led to the development of various classes of nanostructured carriers customized to overcome these limitations. This work systematically reviews the current advances in developing the next generation of drugs based on nanotechnology-assisted RNA delivery. The features of the most used RNA molecules are presented, together with the development strategies and properties of nanostructured vehicles. Also provided is an in-depth overview of various therapeutic applications of the presented systems, including coronavirus disease vaccines and the newest trends in the field. Lastly, emerging challenges and future perspectives for nanotechnology-mediated RNA therapies are discussed.

Tailoring the Architecture of Cationic Polymer Brush-Modified Carbon Nanotubes for Efficient siRNA Delivery in Cancer Immunotherapy

The facile and controlled fabrication of homogeneously grafted cationic polymers on carbon nanotubes (CNTs) remains poorly investigated, which further hinders the understanding of interactions between functionalized CNTs with different nucleic acids and the rational design of appropriate gene delivery vehicles. Herein, we describe the controlled grafting of cationic poly(2-dimethylaminoethylmethacrylate) brushes on CNTs via surface-initiated atom transfer radical polymerization integrated with mussel-inspired polydopamine chemistry. The binding of nucleic acids with different brush-CNT hybrids discloses the highly architectural-dependent behavior with dense short brush-coated CNTs displaying the highest binding among all the other hybrids, namely, dense long, sparse long, and sparse short brush-coated CNTs. Additionally, different chemistries of the brush coatings were shown to influence the biocompatibility, cellular uptake, and silencing efficiency in vitro. This platform provides great flexibility for the design of polymer brush-CNT hybrids with precise control over their structure-activity relationship for the rational design of nucleic acid delivery systems.

Non-viral nanoparticles for RNA interference: Principles of design and practical guidelines

Ribonucleic acid interference (RNAi) is an innovative treatment strategy for a myriad of indications. Non-viral synthetic nanoparticles (NPs) have drawn extensive attention as vectors for RNAi due to their potential advantages, including improved safety, high delivery efficiency and economic feasibility. However, the complex natural process of RNAi and the susceptible nature of oligonucleotides render the NPs subject to particular design principles and requirements for practical fabrication. Here, we summarize the requirements and obstacles for fabricating non-viral nano-vectors for efficient RNAi. To address the delivery challenges, we discuss practical guidelines for materials selection and NP synthesis in order to maximize RNA encapsulation efficiency and protection against degradation, and to facilitate the cytosolic release of oligonucleotides. The current status of clinical translation of RNAi-based therapies and further perspectives for reducing the potential side effects are also reviewed.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Responsive Polymer Brush Design and Emerging Applications for Nanotheranostics

Responsive polymer brushes are a category of polymer brushes that are capable of conformational and chemical changes in response to external stimuli. They offer unique opportunities for the control of bio-nano interactions due to the precise control of chemical and structural parameters such as the brush thickness, density, chemistry, and architecture. The design of responsive brushes at the surface of nanomaterials for theranostic applications has developed rapidly. These coatings can be generated from a very broad range of nanomaterials, without compromising their physical, photophysical, and imaging properties. Although the use of responsive brushes for nanotheranostic remains in its early stages, in this review, the aim is to present how the systems developed to date can be combined to control sensing, imaging, and controlled delivery of therapeutics. The recent developments for such design and associated methods for the synthesis of responsive brushes are discussed. The responsive behaviors of homo polymer brushes and brushes with more complex architectures are briefly reviewed, before the applications of responsive brushes as smart delivery systems are discussed. Finally, the recent work is summarized on the use of responsive polymer brushes as novel biosensors and diagnostic tools for the detection of analytes and biomarkers.

Peptide-Engineered Fluorescent Nanomaterials: Structure Design, Function Tailoring, and Biomedical Applications

Fluorescent nanomaterials have exhibited promising applications in biomedical and tissue engineering fields. To improve the properties and expand bioapplications of fluorescent nanomaterials, various functionalization and biomodification strategies have been utilized to engineer the structure and function of fluorescent nanomaterials. Due to their high biocompatibility, satisfied bioactivity, unique biomimetic function, easy structural tailoring, and controlled self-assembly ability, supramolecular peptides are widely used as versatile modification agents and nanoscale building blocks for engineering fluorescent nanomaterials. In this work, recent advance in the synthesis, structure, function, and biomedical applications of peptide-engineered fluorescent nanomaterials is presented. Firstly, the types of different fluorescent nanomaterials are introduced. Then, potential strategies for the preparation of peptide-engineered fluorescent nanomaterials via templated synthesis, bioinspired conjugation, and peptide assembly-assisted synthesis are discussed. After that, the unique structure and functions through the peptide conjugation with fluorescent nanomaterials are demonstrated. Finally, the biomedical applications of peptide-engineered fluorescent nanomaterials in bioimaging, disease diagnostics and therapy, drug delivery, tissue engineering, antimicrobial test, and biosensing are presented and discussed in detail. It is helpful for readers to understand the peptide-based conjugation and bioinspired synthesis of fluorescent nanomaterials, and to design and synthesize novel hybrid bionanomaterials with special structures and improved functions for advanced applications.

A Fluorescent Polyurethane with Covalently Cross-Linked Rhodamine Derivatives

Rhodamine derivatives (RDs) with three reactive hydrogens were synthesized and well characterized by Fourier transform infra-red spectroscopy (FTIR), 1H nuclear magnetic resonance (1H NMR) and electrospray ionization mass spectra (ESI mass). Then, the obtained RD was covalently cross-linked into polyurethane (PU) matrix through chemical linkages to fabricate a network structure, and the fluorescent properties, mechanical properties, thermal stability, and emulsion particle size were systematically investigated. Results demonstrate that PU-RD maintains initial fluorescent properties and emits desirable yellow fluorescence under ultraviolet irradiation. Moreover, compared with linear PU without fluorescers, PU-RD shows clearly improved mechanical properties and thermal stability, on account of the formed network structures.