Boronic ester-based self-healing hydrogels formed by using intermolecular B-N coordination

Progress in the preparation and evaluation of glucose-sensitive microneedle systems and their blood glucose regulation

Glucose-sensitive microneedle systems (GSMSs) as an intelligent strategy for treating diabetes can well solve the problems of puncture pain, hypoglycemia, skin damage, and complications caused by the subcutaneous injection of insulin. According to the various functions of each component, herein, therapeutic GSMSs are reviewed based on three parts (glucose-sensitive models, diabetes medications, and microneedle body). Moreover, the characteristics, benefits, and drawbacks of three types of typical glucose-sensitive models (phenylboronic acid based polymer, glucose oxidase, and concanavalin A) and their drug delivery models are reviewed. In particular, phenylboronic acid-based GSMSs can provide a long-acting drug dose and controlled release rate for the treatment of diabetes. Moreover, their painless, minimally invasive puncture also greatly improves patient compliance, treatment safety, and potential application prospects.

Photo-Crosslinked Coumarin-Containing Bis-Urea Amphiphile Hydrogels

The design of photo-responsive supramolecular hydrogels based on coumarin dimerization and de-dimerization is described. The photo-responsive coumarin unit is chemically incorporated into an oligo(ethylene glycol) (OEG) bis-urea amphiphile that is capable of co-assembling with non-functionalized OEG amphiphile, to form supramolecular fibers. UV light with two different wavelengths (365 nm and 254 nm) is employed to induce a photo-reversible dimerization and de-dimerization process of coumarin units, respectively. The co-assembled solutions could be photo-crosslinked to induce a sol-to-gel transition through dimerization of coumarin with 365 nm UV light, and de-dimerization occurs with 254 nm UV light, to provide a weaker gel. In this system, the mechanical strength of supramolecular hydrogels can be tuned using the irradiation time, providing precise control of gelation in a supramolecular hydrogelator.

Current Trends in Biomedical Hydrogels: From Traditional Crosslinking to Plasma-Assisted Synthesis

The use of materials to restore or replace the functions of damaged body parts has been proven historically. Any material can be considered as a biomaterial as long as it performs its biological function and does not cause adverse effects to the host. With the increasing demands for biofunctionality, biomaterials nowadays may not only encompass inertness but also specialized utility towards the target biological application. A hydrogel is a biomaterial with a 3D network made of hydrophilic polymers. It is regarded as one of the earliest biomaterials developed for human use. The preparation of hydrogel is often attributed to the polymerization of monomers or crosslinking of hydrophilic polymers to achieve the desired ability to hold large amounts of aqueous solvents and biological fluids. The generation of hydrogels, however, is shifting towards developing hydrogels through the aid of enabling technologies. This review provides the evolution of hydrogels and the different approaches considered for hydrogel preparation. Further, this review presents the plasma process as an enabling technology for tailoring hydrogel properties. The mechanism of plasma-assisted treatment during hydrogel synthesis and the current use of the plasma-treated hydrogels are also discussed.

Protodeboronation of (Hetero)Arylboronic Esters: Direct versus Prehydrolytic Pathways and Self-/Auto-Catalysis

The kinetics and mechanism of the base-catalyzed hydrolysis (ArB(OR)₂ → ArB(OH)₂) and protodeboronation (ArB(OR)₂ → ArH) of a series of boronic esters, encompassing eight different polyols and 10 polyfluoroaryl and heteroaryl moieties, have been investigated by in situ and stopped-flow NMR spectroscopy (¹⁹F, ¹H, and ¹¹B), pH-rate dependence, isotope entrainment, ²H KIEs, and KS-DFT computations. The study reveals the phenomenological stability of boronic esters under basic aqueous-organic conditions to be highly nuanced. In contrast to common assumption, esterification does not necessarily impart greater stability compared to the corresponding boronic acid. Moreover, hydrolysis of the ester to the boronic acid can be a dominant component of the overall protodeboronation process, augmented by self-, auto-, and oxidative (phenolic) catalysis when the pH is close to the pK_a of the boronic acid/ester.

Indocyanine green loaded pH-responsive bortezomib supramolecular hydrogel for synergistic chemo-photothermal/photodynamic colorectal cancer therapy

Colorectal cancer is with high incidence worlwide.. Because of the heterogeneity of the tumor, combination therapy is probably of great significance to improve the prognosis of colorectal cancer patients. Herein, the pH-responsive supramolecular hydrogels mPEG-luteolin-BTZ@ICG based on bortezomib (BTZ) and indocyanine green (ICG) were prepared, and the colorectal cancer was treated with mPEG-luteolin-BTZ@ICG through the combination of photothermal/photodynamic and chemotherapy. BTZ performed drug therapy, meanwhile ICG wrapped in supramolecular hydrogels possessed higher light stability than free ICG to perform photothermal/photodynamic therapy. In vitro and in vivo assays showed excellent inhibition of tumor cells due to the combined effect of BTZ and ICG. The mPEG-luteolin-BTZ@ICG combined with laser therapy possessed exceptional biological safety and provided new candidates for advanced colon cancer therapy and important references for other tumor therapies.

Serially pH-Modulated Hydrogels Based on Boronate Ester and Polydopamine Linkages for Local Cancer Therapy

Elaborately and serially pH-modulated hydrogels possessing optimized viscoelastic natures for short gelation time and single syringe injection were designed for peritumoral injection of an anticancer agent. Boronate ester bonds between phenylboronic acid (PBA) (installed in HA-PBA (HP)) and dopamine (included in HA-dopamine (HD)) along with self-polymerization of dopamine (via interactions between HD conjugates) were introduced as the main cross-linking strategies of a hyaluronic acid (HA) hydrogel. Considering pK_a values (8.0-9.5) of PBA and dopamine, the pH of each polymer dispersion was controlled elaborately for injection through a single syringe, and the final pH was tuned nearby the physiological pH (pH 7.8). The shear-thinning behavior, self-healing property, and single syringe injectability of a designed hydrogel cross-linked nearby physiological pH may provide its convenient application to peritumoral injection and prolonged retention in local cancer therapy. Erlotinib (ERT) was encapsulated in a microsphere (MS), and it was further embedded in an HP/HD-based hydrogel for sustained and locoregional delivery. A rheologically tuned hydrogel containing an ERT MS exhibited superior tumor-suppressive efficiencies compared to the other groups in A549 tumor-bearing mice. A designed injectable hydrogel through a single syringe system may be efficiently applied to local cancer therapy with lower toxicities to healthy organs.