Multivalent and multifunctional polysaccharide-based particles for controlled receptor recognition

Thermoresponsive Core-cross-linked Nanoparticles from HA-b-ELP Diblock Copolymers

Stabilization against the dilution-dependent disassembly of self-assembled nanoparticles is a requirement for in vivo application. Herein, we propose a simple and biocompatible cross-linking reaction for the stabilization of a series of nanoparticles formed by the self-assembly of amphiphilic HA-b-ELP block copolymers, through the alkylation of methionine residues from the ELP block with diglycidyl ether compounds. The core-cross-linked nanoparticles retain their colloidal properties, with a spherical core-shell morphology, while maintaining thermoresponsive behavior. As such, instead of a reversible disassembly when non-cross-linked, a reversible swelling of nanoparticles' core and increase of hydrodynamic diameter are observed with lowering of the temperature.

Terminus-Selective Covalent Immobilization of Heparin on a Thermoresponsive Surface Using Click Chemistry for Efficient Binding of Basic Fibroblast Growth Factor

Cell therapy using endothelial cells (ECs) has great potential for the treatment of congenital disorders, such as hemophilia A. Cell sheet technology utilizing a thermoresponsive culture dish is a promising approach to efficiently transplant donor cells. In this study, a new method to prepare terminus-selective heparin-immobilized thermoresponsive culture surfaces is developed to facilitate the preparation of EC sheets. Alkynes are introduced to the reducing terminus of heparin via reductive amination. Cu-catalyzed azide-alkyne cycloaddition (CuAAC) facilitates efficient immobilization of the terminus of heparin on a thermoresponsive surface, resulting in a higher amount of immobilized heparin while preserving its function. Heparin-immobilized thermoresponsive surfaces prepared using CuAAC exhibit good adhesion to human endothelial colony-forming cells (ECFCs). In addition, upon further binding to basic fibroblast growth factor (bFGF) on heparin-immobilized surfaces, increased proliferation of ECFCs on the surface is observed. The confluent ECFC monolayer cultured on bFGF-bound heparin-immobilized thermoresponsive surfaces exhibits relatively high fibronectin accumulation and cell number and detaches at 22 °C while maintaining the sheet-like structure. Because heparin has an affinity for several types of bioactive molecules, the proposed method can be applied to facilitate efficient cultures and sheet formations of various cell types.

Transcription-Factor-Induced Aggregation of Biomimetic Oligonucleotide-b-Protein Micelles

Polymeric micelles and especially those based on natural diblocks are of particular interest due to their advantageous properties in terms of molecular recognition, biocompatibility, and biodegradability. We herein report a facile and straightforward synthesis of thermoresponsive elastin-like polypeptide (ELP) and oligonucleotide (ON) diblock bioconjugates, ON-b-ELP, through copper-catalyzed azide-alkyne cycloaddition. The resulting thermosensitive diblock copolymer self-assembles above its critical micelle temperature (CMT ∼30 °C) to form colloidally stable micelles of ∼50 nm diameter. The ON-b-ELP micelles hybridize with an ON complementary strand and maintain their size and stability. Next, we describe the capacity of these micelles to bind proteins, creating more complex structures using the classic biotin-streptavidin pairing and the specific recognition between a transcription factor protein and the ON strand. In both instances, the micelles are intact, form larger structures, and retain their sensitivity to temperature.

Enhancing the Drug-Like Profile of a Potent Peptide PACE4 Inhibitor by the Formation of a Host-Guest Inclusion Complex with β-Cyclodextrin

The enzyme PACE4 has been validated as a promising therapeutic target to expand the range of prostate cancer (PCa) treatments. In recent years, we have developed a potent peptidomimetic inhibitor, namely, compound C23 (Ac-(DLeu)LLLRVK-4-amidinobenzylamide). Like many peptides, C23 suffers from an unfavorable drug-like profile which, despite our efforts, has not yet benefited from the usual SAR studies. Hence, we turned our attention toward a novel formulation strategy, i.e., the use of cyclodextrins (CDs). CDs can benefit compounds through the formation of "host-guest" complexes, shielding the guest from degradation and enhancing biological survival. In this study, a series of βCD-C23 complexes have been generated and their properties evaluated, including potency toward the enzyme in vitro, a cell-based proliferation assay, and stability in plasma. As a result, a new βCD-formulated lead compound has been identified, which, in addition to being more soluble and more potent, also showed an improved stability profile.

Codelivery of BCL2 and MCL1 Inhibitors Enabled by Phenylboronic Acid-Functionalized Polypeptide Nanovehicles for Synergetic and Potent Therapy of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is the most refractory hematologic malignancy characterized by acute onset, rapid progression, and high recurrence rate. Here, codelivery of BCL2 (ABT199) and MCL1 (TW37) inhibitors using phenylboronic acid-functionalized polypeptide nanovehicles to achieve synergetic and potent treatment of AML is adopted. Leveraging the dynamic boronic ester bonds, BN coordination, and π-π stacking, the nanovehicles reveal remarkably efficient and robust drug coencapsulation. ABT199 can induce a series of pro-apoptotic reactions by promoting the dissociation of the pro-apoptotic protein Bim from BCL2, while the released Bim is often captured by MCL1 protein overexpressed in AML. TW37 has a strong inhibitory ability to MCL1, thereby can restrain the depletion of Bim protein. Dual inhibitor-loaded nanoparticles (NPAT) reveal excellent stability, acid/enzyme/H₂ O₂ -triggered drug release, and significant cytotoxicity toward MOLM-13-Luc and MV-411 AML cells with low half maximal inhibitory concentrations of 1.15 and 7.45 ng mL^-1 , respectively. In mice bearing MOLM-13-Luc or MV-411 AML cancer, NPAT reveal significant inhibition of tumor cell infiltration in bone marrow and main organs, potent suppression of tumor growth, and remarkably elevated mouse survival. With facile construction, varying drug combination, superior safety, synergetic efficacy, the phenylboronic acid-functionalized smart nanodrugs hold remarkable potential for AML treatment.

Green approaches for extraction, chemical modification and processing of marine polysaccharides for biomedical applications

Over the past few decades, natural-origin polysaccharides have received increasing attention across different fields of application, including biomedicine and biotechnology, because of their specific physicochemical and biological properties that have afforded the fabrication of a plethora of multifunctional devices for healthcare applications. More recently, marine raw materials from fisheries and aquaculture have emerged as a highly sustainable approach to convert marine biomass into added-value polysaccharides for human benefit. Nowadays, significant efforts have been made to combine such circular bio-based approach with cost-effective and environmentally-friendly technologies that enable the isolation of marine-origin polysaccharides up to the final construction of a biomedical device, thus developing an entirely sustainable pipeline. In this regard, the present review intends to provide an up-to-date outlook on the current green extraction methodologies of marine-origin polysaccharides and their molecular engineering toolbox for designing a multitude of biomaterial platforms for healthcare. Furthermore, we discuss how to foster circular bio-based approaches to pursue the further development of added-value biomedical devices, while preserving the marine ecosystem.

Emerging opportunities in bioconjugates of Elastin-like polypeptides with synthetic or natural polymers

Nature is an everlasting source of inspiration for chemical and polymer scientists seeking to develop ever more innovative materials with greater performances. Natural structural proteins are particularly scrutinized to design biomimetic materials. Often characterized by repeat peptide sequences, that together interact by inter- and intramolecular interactions and form a 3D skeleton, they contribute to the mechanical properties of individual cells, tissues, organs, and whole organisms. (Numata, K. Polymer Journal 2020, 52, 1043-1056) Among them elastin, and its main repeat sequences, have been a source of intense studies for more than 50 years resulting in the specific research field dedicated to elastin-like polypeptides (ELPs). These are currently widely investigated in different applications, namely protein purification, tissue engineering, and drug delivery, and some technologies based on ELPs are currently explored by several start-up companies. In the present review, we have summarized pioneering contributions on ELPs, progress made in their genetic engineering, and understanding of their thermal behavior and self-assembly properties. Considered as intrinsically disordered protein polymers, we have finally focused on the works where ELPs have been conjugated to other synthetic macromolecules as covalent hybrid, statistical, graft, or block copolymers, highlighting the huge opportunities that have still not been explored so far.

Aqueous synthesis and self-assembly of bioactive and thermo-responsive HA-b-ELP bioconjugates

The design of synthetic (bio)macromolecules that combine biocompatibility, self-assembly and bioactivity properties at the molecular level is an intense field of research for biomedical applications such as (nano)medicine. In this contribution, we have designed and synthesized a library of bioactive and thermo-responsive bioconjugates from elastin-like polypeptides (ELPs) and hyaluronic acid (HA) in order to access bioactive self-assembled nanoparticles. These were prepared by a simple synthetic and purification strategy, compatible with the requirements for biological applications and industrial scale-up. A series of 9 HA-b-ELP bioconjugates with different compositions and block lengths was synthesized under aqueous conditions by strain-promoted azide-alkyne cycloaddition (SPAAC), avoiding the use of catalysts, co-reactants and organic solvents, and isolated by a simple centrifugation step. An extensive physico-chemical study was then performed on the whole library of bioconjugates in an attempt to establish structure-property relationships. In particular, the determination of the critical conditions for thermally driven self-assembly was carried out upon temperature (CMT) and concentration (CMC) gradients, leading to a phase diagram for each of these bioconjugates. These parameters and the size of nanoparticles were found to depend on the chemical composition of the bioconjugates, namely on the respective size of individual blocks. Understanding the mechanism underlying this dependency is a real asset for designing more effective experiments: with key criteria defined (e.g. concentration, temperature, salinity, and biological target), the composition of the best candidates can be rationalized. In particular, four of the bioconjugates (HA_4.6k-ELPn80 or n100 and HA_24k-ELPn80 or n100) were found to self-assemble into well-defined spherical core-shell nanoparticles, with a negative surface charge due to the HA block exposed at the surface, a hydrodynamic diameter between 40 and 200 nm under physiological conditions and a good stability over time at 37 °C. We therefore propose here a versatile and simple design of smart, controllable, and bioactive nanoparticles that present different behaviors depending on the diblocks' composition.

Hyaluronan Brush-like Copolymers Promote CD44 Declustering in Breast Cancer Cells

We report on the synthesis of hyaluronan (HA) brush-like copolymers and their application as antagonists of tumorigenic CD44-HA interactions. HA (4.8 kDa, ca. 24 saccharides) was grafted on 2-hydrohyethyl methacrylate (HEMA) by end-on oxime ligation. The obtained copolymers were compared with low and high molecular weight HA in terms of hydrolysis kinetics in the presence of hyaluronidase (isothermal titration calorimetry) and interactions with CD44 (surface plasmon resonance). The results evidenced that the high molecular weight HA and HA-g-HEMA have a much higher affinity to CD44 than low molecular weight HA. Additionally, slower enzymatic degradation was observed for the copolymer, making it an excellent candidate for active targeting of tumorigenic CD44-HA interactions. We, therefore, investigated the effect of the copolymer on cancer cell lines with different expression of CD44 and observed an efficient declustering of CD44 that is usually associated with reduction of metastasis and drug resistance.

Thermoresponsive Glycopolypeptide Containing Block Copolymers, Particle Formation, and Lectin Interaction

Amphiphilic block copolymers with a thermoresponsive poly(N-isopropylacrylamide) block and a glycopeptide block are synthesized and particle formation as well as interaction of the glyco-corona with lectins is investigated. The synthetic route comprises the preparation of block copolymers by N-carboxyanhydride polymerization and subsequent deprotection to obtain pH- and thermoresponsive poly(l-glutamic acid)-b-poly(N-isopropylacrylamide) (pGA-b-pNIPAM), which is then further modified with different amino sugars by a versatile coupling method with 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholin-4-ium chloride (DMT-MM). The glycosylated pGA-b-pNIPAM block copolymers are investigated with regard to cloud point temperatures (T_cp ), particle size, and stability. The morphology of the particles is visualized using cryo-SEM. Zeta potential measurements are indicating that the saccharide moieties are located on the surface of the particles. This assumption is further substantiated by quantitative lectin interaction assays with nonaggregated and aggregated glycosylated pGA-b-pNIPAM. The interaction of the model lectin ConA with the block copolymers is independent of the degree of substitution in the nonaggregated state at room temperature. However, at 37 °C, when particles of pGA-b-pNIPAM are present, the interaction becomes stronger with increasing degree of substitution. This interaction with lectins can be used for targeting saccharide-modified particles in drug delivery.

Embracing nanomaterials' interactions with the innate immune system

Immunotherapy has firmly established itself as a compelling avenue for treating disease. Although many clinically approved immunotherapeutics engage the adaptive immune system, therapeutically targeting the innate immune system remains much less explored. Nanomedicine offers a compelling opportunity for innate immune system engagement, as many nanomaterials inherently interact with myeloid cells (e.g., monocytes, macrophages, neutrophils, and dendritic cells) or can be functionalized to target their cell-surface receptors. Here, we provide a perspective on exploiting nanomaterials for innate immune system regulation. We focus on specific nanomaterial design parameters, including size, form, rigidity, charge, and surface decoration. Furthermore, we examine the potential of high-throughput screening and machine learning, while also providing recommendations for advancing the field. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

pH-Sensitive branched β-glucan-modified liposomes for activation of antigen presenting cells and induction of antitumor immunity

Induction of cellular immunity is important for effective cancer immunotherapy. Although various antigen carriers for cancer immunotherapy have been developed to date, balancing efficient antigen delivery to antigen presenting cells (APCs) and their activation via innate immune receptors, both of which are crucially important for the induction of strong cellular immunity, remains challenging. For this study, branched β-glucan was selected as an intrinsically immunity-stimulating and biocompatible material. It was engineered to develop multifunctional liposomal cancer vaccines capable of efficient interactions with APCs and subsequent activation of the cells. Hydroxy groups of branched β-glucan (Aquaβ) were modified with 3-methylglutaric acid ester and decyl groups, respectively, to provide pH-sensitivity and anchoring capability to the liposomal membrane. The modification efficiency of Aquaβ derivatives to the liposomes was significantly high compared with linear β-glucan (curdlan) derivatives. Aquaβ derivative-modified liposomes released their contents in response to weakly acidic pH. As a model antigenic protein, ovalbumin (OVA)-loaded liposomes modified with Aquaβ derivatives interacted efficiently with dendritic cells, and induced inflammatory cytokine secretion from the cells. Subcutaneous administration of Aquaβ derivative-modified liposomes suppressed the growth of the E.G7-OVA tumor significantly compared with curdlan derivative-modified liposomes. Aquaβ derivative-modified liposomes induced the increase of CD8⁺ T cells, and polarized macrophages to the antitumor M1-phenotype within the tumor microenvironment. Therefore, pH-sensitive Aquaβ derivatives can be promising materials for liposomal antigen delivery systems to induce antitumor immune responses efficiently.

Immune activities of polysaccharides isolated from Lycium barbarum L. What do we know so far?

Lycium barbarum is widely used as a functional food and medicinal herb to promote health and longevity in China and in some other Asian countries. In modern pharmacological and chemical studies, the most valuable and well-researched component of L. barbarum is a group of unique water-soluble glycoconjugates that are collectively termed Lycium barbarum polysaccharides (LBPs). Numerous modern pharmacological studies have revealed that LBPs possess antiaging, antidiabetic, antifibrotic, neuroprotective, and immunomodulation properties, while the immunomodulatory effect is primary and is involved in other activities. However, due to their structural heterogeneity and lack of chromophores, it has long been unclear how LBPs work on the immune system. A few studies have recently provided some insights into the proposed mode of action of LBPs, such as structure-activity relationships, receptor recognition, and gut microbiota modulation of LBPs. This review provides a comprehensive overview of the immunoregulating properties of LBPs and their related mechanisms of action.

Revolutionizing polymer-based nanoparticle-linked vaccines for targeting respiratory viruses: A perspective

Viral respiratory tract infections have significantly impacted global health as well as socio-economic growth. Respiratory viruses such as the influenza virus, respiratory syncytial virus (RSV), and the recent SARS-CoV-2 infection (COVID-19) typically infect the upper respiratory tract by entry through the respiratory mucosa before reaching the lower respiratory tract, resulting in respiratory disease. Generally, vaccination is the primary method in preventing virus pathogenicity and it has been shown to remarkably reduce the burden of various infectious diseases. Nevertheless, the efficacy of conventional vaccines may be hindered by certain limitations, prompting the need to develop novel vaccine delivery vehicles to immunize against various strains of respiratory viruses and to mitigate the risk of a pandemic. In this review, we provide an insight into how polymer-based nanoparticles can be integrated with the development of vaccines to effectively enhance immune responses for combating viral respiratory tract infections.

Role of the interactions of soft hyaluronan nanomaterials with CD44 and supported bilayer membranes in the cellular uptake

Increasing valence by acting on nanomaterial morphology can enhance the ability of a ligand to specifically bind to targeted cells. Herein, we investigated cell internalization of soft hyaluronic acid (HA) nanoplatelets (NPs) that exhibit a typical hexagonal shape, flat surfaces and high aspect ratio (Γ≈12 to 20), as characterized by atomic force microscopy in hydrated conditions. Fluorescence imaging revealed that internalization of HA-NPs by a T24 tumor cell line and by macrophages was higher than native polysaccharide in a dose-dependent and time-dependent manners. The ability of HA-NPs to efficiently compete with native HA assessed using Bio-layer interferometry showed that NPs had a stronger interaction with recombinant CD44 receptor compared to native HA. The results were discussed regarding physical properties of the NPs and the implication of multivalent interactions in HA binding to CD44. Experiments conducted on supported bilayer membranes with different compositions showed that non-specific interactions of NPs with lipid membranes were negligible. Our findings provide insights into intracellular drug delivery using soft HA-NPs through receptor-mediated multivalent interactions.

Control of Particle Size in the Self-Assembly of Amphiphilic Statistical Copolymers

A range of amphiphilic statistical copolymers is synthesized where the hydrophilic component is either methacrylic acid (MAA) or 2-(dimethylamino)ethyl methacrylate (DMAEMA) and the hydrophobic component comprises methyl, ethyl, butyl, hexyl, or 2-ethylhexyl methacrylate, which provide a broad range of partition coefficients (log P). Small-angle X-ray scattering studies confirm that these amphiphilic copolymers self-assemble to form well-defined spherical nanoparticles in an aqueous solution, with more hydrophobic copolymers forming larger nanoparticles. Varying the nature of the alkyl substituent also influenced self-assembly with more hydrophobic comonomers producing larger nanoparticles at a given copolymer composition. A model based on particle surface charge density (PSC model) is used to describe the relationship between copolymer composition and nanoparticle size. This model assumes that the hydrophilic monomer is preferentially located at the particle surface and provides a good fit to all of the experimental data. More specifically, a linear relationship is observed between the surface area fraction covered by the hydrophilic comonomer required to achieve stabilization and the log P value for the hydrophobic comonomer. Contrast variation small-angle neutron scattering is used to study the internal structure of these nanoparticles. This technique indicates partial phase separation within the nanoparticles, with about half of the available hydrophilic comonomer repeat units being located at the surface and hydrophobic comonomer-rich cores. This information enables a refined PSC model to be developed, which indicates the same relationship between the surface area fraction of the hydrophilic comonomer and the log P of the hydrophobic comonomer repeat units for the anionic (MAA) and cationic (DMAEMA) comonomer systems. This study demonstrates how nanoparticle size can be readily controlled and predicted using relatively ill-defined statistical copolymers, making such systems a viable attractive alternative to diblock copolymer nanoparticles for a range of industrial applications.

Self-assembly of dextran - b - deoxycholic acid polyester copolymers: Copolymer composition and self-assembly procedure tune the aggregate size and morphology

Self-assembly potential of new amphiphilic block copolymers containing dextran (M_n 4500, 8000, 15,000) and a semi-rigid deoxycholic acid-oligoethyleneglycol polyester (M_n 2500-8800, 2 or 4 ethyleneglycol units), was evaluated as a function of copolymer composition and self-assembly procedure, using dynamic light scattering and transmission electron microscopy. Addition of copolymer solution to water provided small star-like micelles (∼ 100 nm), while addition of water to copolymer solution led to various morphologies and sizes (60-600 nm), depending on polymer composition. Worm-like micelles were obtained from a copolymer containing dextran with M_n 4500 and 66 wt% polyester, and vesicles were formed by copolymers prepared from dextran with M_n 8000 and containing 46 wt% polyester. Presence of a longer oligoethyleneglycol decreased the size of micelles and vesicles due to an enhanced flexibility of the polyester hydrophobic block. The results allow the selection of the most appropriate parameters to obtain the desired aggregate characteristics.

Amphiphilic Nucleobase-Containing Polypeptide Copolymers-Synthesis and Self-Assembly

Nucleobase-containing polymers are an emerging class of building blocks for the self-assembly of nanoobjects with promising applications in nanomedicine and biology. Here we present a macromolecular engineering approach to design nucleobase-containing polypeptide polymers incorporating thymine that further self-assemble in nanomaterials. Diblock and triblock copolypeptide polymers were prepared using sequential ring-opening polymerization of γ-Benzyl-l-glutamate N-carboxyanhydride (BLG-NCA) and γ-Propargyl-l-glutamate N-carboxyanhydride (PLG-NCA), followed by an efficient copper(I)-catalyzed azide alkyne cycloaddition (CuAAc) functionalization with thymidine monophosphate. Resulting amphiphilic copolymers were able to spontaneously form nanoobjects in aqueous solutions avoiding a pre-solubilization step with an organic solvent. Upon self-assembly, light scattering measurements and transmission electron microscopy (TEM) revealed the impact of the architecture (diblock versus triblock) on the morphology of the resulted nanoassemblies. Interestingly, the nucleobase-containing nanoobjects displayed free thymine units in the shell that were found available for further DNA-binding.

Ring opening polymerization of α-amino acids: advances in synthesis, architecture and applications of polypeptides and their hybrids

This review provides a comprehensive overview of the latest advances in the synthesis, architectural design and biomedical applications of polypeptides and their hybrids.

Biomedical applications of laminarin

The ocean is par excellence a fertile territory of biodiversity on our planet. Marine-derived polysaccharides have been applied as functional materials in biomedicine due to their attractive bioactive properties, safety, high availability and low-cost production. Laminarin (or laminaran), a low molecular weight β-glucan storage polysaccharide present in brown algae, can be (bio-) chemically modified to enhance its biological activity and employed in cancer therapies, drug/gene delivery, tissue engineering, antioxidant and anti-inflammatory functions. This review provides a brief overview on laminarin characteristics, modification strategies and highlights its pivotal biomedical applications.

Copolymers containing carbohydrates and other biomolecules: design, synthesis and applications

This review highlights recent progress in random and block copolymers containing sugar and other biocompounds, including their design, synthesis, properties and selected applications.