Gossypol-cross-linked boronic acid-modified hydrogels: a functional matrix for the controlled release of an anticancer drug

A novel triple-network hydrogel based on borate ester groups: from structural modulation to rapid wound hemostasis

Supramolecular hydrogels have received widespread attention due to their soft texture, strong hygroscopicity, and good biocompatibility. These materials have become particularly attractive for sensing, tissue engineering, fluorescence encoding, wound healing, etc. Inspired by the assembly of G-quadruplexes, we choose the boric acid/polyvinyl alcohol/guanosine system to construct a novel triple-network supramolecular hydrogel "tri-BA@PVA/G" via non-covalent cross-linking, and the effect of the concentration of each component on the hydrogel stability was systematically revealed at the same time. Then, the biocompatibility, shape adaption and optical information storage capacity, the rapid hemostatic ability and the ability of the hydrogel to promote wound healing were confirmed both in vitro and in vivo. These results that predict the properties and reveal prospective applications in the field of wound hemostasis have a certain guiding significance for the subsequent preparation of borate-based triple network hydrogels which can be used as wound hemostatic materials.

Boron-enriched polyvinyl-alcohol/boric-acid nanoparticles for boron neutron capture therapy

Background: Due to the noninvasive nature of boron neutron capture therapy (BNCT), it is considered a promising cancer treatment method. Aim: To investigate whether polyvinyl alcohol/boric acid crosslinked nanoparticles (PVA/BA NPs) are an efficient delivery system for BNCT. Materials & methods: PVA/BA NPs were synthesized and cocultured with brain and oral cancers cells for BNCT. Results: PVA/BA NPs had a boron-loading capacity of 7.83 ± 1.75 w/w%. They accumulated in brain and oral cancers cells at least threefold more than in fibroblasts and macrophages. The IC50 values of the brain and oral cancers cells were at least ninefold and sixfold lower than those of fibroblasts and macrophages, respectively. Conclusion: Theoretically, PVA/BA NPs target brain and oral cancers cells and could offer improved therapeutic outcomes of BNCT.

Nature-inspired semi-IPN hydrogels with tunable mechanical properties and multi-responsiveness

Tough hydrogels (PAP hydrogels) with high mechanical properties and multi-responsiveness.

Boronate-ester crosslinked hyaluronic acid hydrogels for dihydrocaffeic acid delivery and fibroblasts protection against UVB irradiation

Herein, we exploit the dynamic nature and pH dependence of complexes between phenylboronic acid and diol-containing molecules to control the release of an anti-photoaging agent, dihydrocaffeic acid (DHCA), from a dynamic covalent hydrogel (HG). The HG is prepared by reversible formation of boronate ester crosslinks between hyaluronic acid (HA) modified with saccharide (GLU) residues and HA functionalized with 3-aminophenylboronic acid (APBA), part of which is involved in complexation with DHCA. The hydrogel exhibited increased dynamic moduli and a lower relaxation time at pH 7.4 in comparison to pH 6, and greater amount of DHCA was incorporated at pH 7.4. Moreover, this hydrogel prolonged DHCA release at pH 7.4 through drug reversible complexation/decomplexation, while the rate of release was fastest in acidic (skin) conditions. Very interestingly, the incorporation of DHCA into the network enhances its protection against UVB-induced L929 fibroblast death. Therefore, this smart hydrogel can contribute to photoaging prevention.

The Chemistry of Boronic Acids in Nanomaterials for Drug Delivery

Interest in increasing drug delivery efficiency has risen over the past decade both as a means to improve efficacy of already clinically available drugs and due to the increased difficulties of approving new drugs. As a functional group for targeted drug delivery, boronic acids (BAs) have been incorporated in polymeric particles both as a stimuli-responsive functional group and as a targeting ligand. Here, BA chemistry presents a wealth of opportunities for biological applications. It not only reacts with several chemical markers of disease such as reactive oxygen species (ROS), adenosine triphosphate (ATP), glucose, and reduced pH, but it also acts as ligands for diols such as sialic acid. These stimuli-responsive drug delivery systems optimize delivery of therapeutics based on rational design and precise molecular engineering. When designing materials containing BA, the unique chemical properties are important to take into consideration such as its vacant p-orbital, its molecular geometry, and the designed acid's pK_a. Instead of behaving as most carboxylic acids that donate protons, BAs instead primarily act as Lewis acids that accept electrons. In aqueous solution, most polymers containing BA exist in an equilibrium between their triangular hydrophobic form and a tetrahedral hydrophilic form. The most common pK_a's are in the nonphysiological range of 8-10, and much ongoing research focuses on modifying BAs into materials sensitive to a more physiologically relevant pH range. So far, BA moieties have been incorporated into a stunning array of materials, ranging from small molecules that can self-assemble into higher order structures such as micelles and polymeric micelles, via larger polymeric assemblies, to large scale hydrogels. With the abundance of biological molecules containing diols and polyhydroxy motifs, BA-containing materials have proven valuable in several biomedical applications such as treatment of cancer, diabetes, obesity, and bacterial infections. Both materials functionalized with BA and boronic esters display good safety profiles in vitro and in vivo; thus, BA-containing materials represent promising carriers for responsive delivery systems with great potential for clinical translation. The intention of this Account is to showcase the versatility of BA for biomedical applications. We first discuss the chemistry of BA and what to consider when designing BA-containing materials. Further, we review how its chemistry recently has been applied to nanomaterials for enhanced delivery efficiency, both as a stimuli-responsive group and as a targeting ligand. Lastly, we discuss the current limitations and further perspectives of BA in biomaterials, based on the great benefits that can come from utilizing the unique BA chemistry to enhance drug delivery efficiency.

Natural Product Gossypol and its Derivatives in Precision Cancer Medicine

Gossypol, a natural product extracted from the seed, roots, and stem of cotton, was initially used as a male contraceptive but was subsequently investigated as a novel antitumor agent. This review depicts the current status of gossypol and its derivatives as novel antitumor agents as well as presents their preparation and characteristics, especially of some gossypol Schiff bases, through quantitative and structural analysis. The main attractive target sites of gossypol and its derivatives are Bcl-2 family proteins containing the anti-apoptosis proteins Bcl-2 and Bcl-XL. The molecular mechanism of gossypol analogs not only involves cell apoptosis but also autophagy, cell cycle arrest, and other abnormal cellular phenomena. Gossypol and its derivatives exert antitumor effects on different cancer types in vitro and in vivo, and demonstrate synergistic effects with other chemo- and radio- therapeutic treatments. In addition, several nanocarriers have been designed to load gossypol or its derivatives in order to expand the range of their applications and evaluate their combination effects with other anti-tumor agents. This review may serve as a reference for the rational application of gossypol analogs as anti-tumor agents.

Arylboronate esters mediated self-healable and biocompatible dynamic G-quadruplex hydrogels as promising 3D-bioinks

Extrudable G-quadruplex hydrogels were prepared at physiological pH. Gels with suitable mechanical properties were explored as 3D-bioinks. The 3D printing process is driven by injectability and the highly thixotropic and self-healable nature of the gel. High cell viability and homogeneous cell distribution within the gel make it a promising material as a 3D bioink.

Displacement and hybridization reactions in aptamer-functionalized hydrogels for biomimetic protein release and signal transduction

Combinatorial external and internal triggering events enable hydrogel to control protein release by mimicking signal transduction of the cell in response to metabolism.

A variety of hydrogels have been synthesized for controlling the release of signaling molecules in applications such as drug delivery and regenerative medicine. However, it remains challenging to synthesize hydrogels with the ability to control the release of signaling molecules sequentially or periodically under physiological conditions as living cells do in response to the variation of metabolism. The purpose of this work was to study a novel biomimetic hydrogel system with the ability of recapitulating the procedure of cellular signal transduction and controlling the sequential release of signaling molecules under physiological conditions. In the presence of a small chemical, the signaling molecule is regulated to change from a DNA-bound state to a free state and the freed signaling molecule is able to regulate intracellular signal transduction and cell migration. Moreover, periodic exposure of the hydrogel system to the small chemical leads to sequential protein release. Since signaling molecules are important for every activity of the cell, this hydrogel system holds potential as a metabolism-responsive platform for controlled release of signaling molecules and cell regulation in various applications.

Recent advances in gossypol derivatives and analogs: a chemistry and biology view

Gossypol as a natural occurring polyphenol has been studied in a wide range of therapeutic contexts for a long time. The chemical modifications on gossypol were limited due to the unique chemical properties of polyphenols. The design and synthesis of gossypol derivatives and the exploration of their biological activities are the interest of the synthetic chemists, medicinal chemists and pharmacologists. Thus, the progress of diverse gossypol derivatives and analogs' synthesis, biological activities, mechanism elucidation and drug discovery based on gossypol scaffold is summarized.

Multi-responsive, tough and reversible hydrogels with tunable swelling property

A novel family of multi-responsive, tough, and reversible hydrogels were prepared by the combination of dipole-dipole interaction, hydrogen bonding interaction and slightly chemical cross-linking, using monomers of acrylonitrile, sodium allylsulfonate and itaconic acid. Reversible gel-sol transition was achieved by the flexible conversion of the dipole-dipole interactions between acrylonitrile-acrylonitrile and acrylonitrile-sodium thiocyanate, and the hydrogels could freely form desired shapes. The dipole-dipole and hydrogen bonding interactions improved the mechanical strength of the hydrogels with a compressive stress of 2.38MPa. Meanwhile, the hydrogels sustained cyclic compressive tests with 60% strain, and exhibited excellent elastic property. The hydrogels were sensitive to pH and ionic strength, and could keep their perfect spherical structures without any obvious cracks even after immersing in strong ionic strength (or pH) solution for several reversible cycles. Furthermore, the hydrogels were recycled for environmental pollution remediation, and showed great potential to be applied in water treatments and other related fields.

Controlled synthesis of soluble conjugated polymeric nanoparticles for fluorescence detection

Highly fluorescent soluble conjugated polymeric nanoparticles (SCPNs) were synthesized in confined nanoreactors and used for fluorescence sensing of glucose and Fe ion.

Gossypol-Capped Mitoxantrone-Loaded Mesoporous SiO2 NPs for the Cooperative Controlled Release of Two Anti-Cancer Drugs

Mesoporous SiO2 nanoparticles, MP-SiO2 NPs, are functionalized with the boronic acid ligand units. The pores of the MP-SiO2 NPs are loaded with the anticancer drug mitoxantrone, and the pores are capped with the anticancer drug gossypol. The resulting two-drug-functionalized MP-SiO2 NPs provide a potential stimuli-responsive anticancer drug carrier for cooperative chemotherapeutic treatment. In vitro experiments reveal that the MP-SiO2 NPs are unlocked under environmental conditions present in cancer cells, e.g., acidic pH and lactic acid overexpressed in cancer cells. The effective unlocking of the capping units under these conditions is attributed to the acidic hydrolysis of the boronate ester capping units and to the cooperative separation of the boronate ester bridges by the lactate ligand. The gossypol-capped mitoxantrone-loaded MP-SiO2 NPs reveals preferential cytotoxicity toward cancer cells and cooperative chemotherapeutic activities toward the cancer cells. The MCF-10A epithelial breast cells and the malignant MDA-MB-231 breast cancer cells treated with the gossypol-capped mitoxantrone-loaded MP-SiO2 NPs revealed after a time-interval of 5 days a cell death of ca. 8% and 60%, respectively. Also, the gossypol-capped mitoxantrone-loaded MP-SiO2 NPs revealed superior cancer-cell death (ca. 60%) as compared to control carriers consisting of β-cyclodextrin-capped mitoxantrone-loaded (ca. 40%) under similar loading of the mitoxantrone drug. The drugs-loaded MP-SiO2 NPs reveal impressive long-term stabilities.

PDEAEMA-based pH-sensitive amphiphilic pentablock copolymers for controlled anticancer drug delivery

The synthesis of a series of PDEAEMA-based pH-sensitive amphiphilic pentablock copolymers PEG-b-(PDEAEMA-b-PMMA)₂ with different compositions proceeded via the combination of a bromination reaction andARGET ATRP.

A high water-content and high elastic dual-responsive polyurethane hydrogel for drug delivery

Stimuli-responsive hydrogels are soft, biocompatible and smart biomaterials; however, the poor mechanical properties of the hydrogels limit their application. Herein, we prepared a reductant- and light-responsive polyurethane hydrogel which was made of polyethylene glycol, 1,6-diisocyanatohexane, azobenzene, cyclodextrin and disulfide. Attenuated Total Reflectance Infrared Spectra and ¹H NMR were used to characterize the structure of the hydrogel. The hydrogel has a high elasticity (a tensile modulus of 36.5 ± 0.5 kPa and a storage modulus of 52.9 ± 1.2 kPa) at a high water content (91.2 ± 0.4%). Swelling, mechanical and rheological properties of the hydrogel can be tuned by the content of the crosslinker, light and reductant. The hydrogel has low cytotoxicity and it can be used for drug delivery. Ultraviolet irradiation helped to load drugs and the reductant accelerated the drug release. With its high mechanical properties and light- and reductant-responsiveness, the hydrogel is hopefully to be used as a drug carrier.