Leveraging Microgels Prepared from Poly(ethylene glycol) Bisepoxide and Polyetheramine for Versatile Surface Structuring of Agarose Hydrogels

We demonstrate a macromer-type bisepoxide, poly(ethylene glycol) diglycidyl ether, polymerizing readily with a trifunctional polyetheramine Jeffamine T-403 in water to facilitate the development of a series of microgels abbreviated as PMG. Simply by varying the concentration of the as-prepared thermoresponsive intermediate prepolymer from 1 to 2 and 4%, hydrodynamic sizes of the resulting P1MG, P2MG, and P4MG are easily tuned in the submicrometer to micrometer range shown by the dynamic light scattering results. Besides size difference, these microgels also deform differently, where the drying-induced deformation effect is most severe for P1MG and least prominent for P4MG. Simple evaporative deposition of PMG into multilayer packing provides versatile and green options for microgel-mediated surface structuring of agarose hydrogels. Specifically, deformabile P1MG- and P2MG-derived coatings render agarose gel microwrinkle textures by buckling against swelling-induced surface instability. Conversely, stiffer P4MG microgels lead to a patchy patterned hierarchical coating on agarose, similar to the cracking effect in drying colloidal films. The straightforward microgel-on-macrogel strategy allows integration of both wrinkle and patchy patterns to generate Janus-type agarose gels, just by rationally arranging the coating sequence. Diversifying topographic features attainable through microgel-based coatings on hydrogels could potentially make the sustainable and biocompatible material of agarose a more compelling choice for bioapplications. Brief demonstrations of the broad applicability of P1MG toward wrinkling of proteinaceous and synthetic hydrogels further highlight promising prospects of the PMG microgel-on-macrogel functionalization strategy.

pH-Sensitive Polyacrylic Acid-Gated Mesoporous Silica Nanocarrier Incorporated with Calcium Ions for Controlled Drug Release

In this work, polyacrylic acid-functionalized MCM-41 was synthesized, which was made to interact with calcium ions, in order to realize enhanced pH-responsive nanocarriers for sustained drug release. First, mesoporous silica nanoparticles (MSNs) were prepared by the sol-gel method. Afterward, a (3-trimethoxysilyl)propyl methacrylate (TMSPM) modified surface was prepared by using the post-grafting method, and then the polymerization of the acrylic acid was performed. After adding a calcium chloride solution, polyacrylic acid-functionalized MSNs with calcium-carboxyl ionic bonds in the polymeric layer, which can prevent the cargo from leaking out of the mesopore, were prepared. The structure and morphology of the modified nanoparticles (PAA-MSNs) were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), and N₂ adsorption-desorption analysis, etc. The controlled release of guest molecules was studied by using 5-fluorouracil (5-FU). The drug molecule-incorporated nanoparticles showed different releasing rates under different pH conditions. It is considered that our current materials have the potential as pH-responsive nanocarriers in the field of medical treatment.

Various Approaches to Studying the Phase Transition in an Octamethylcyclotetrasiloxane Crystal: From X-ray Structural Analysis to Metadynamics

The structure, thermodynamic parameters, and the character of thermal motion in octamethylcyclotetrasiloxane (D4) were investigated using the combination of experimental (single-crystal X-ray diffraction, thermochemistry) and theoretical (density functional theory calculations, ab initio molecular dynamics and metadynamics) methods. Single crystals of D4 were grown in a glass capillary in situ and the structures of high- (238–270 K) and low-temperature (100–230 K) phases were studied in detail. In the temperature interval 230–238 K, a phase transition with rather low enthalpy (−1.04(7) kcal/mol) was detected. It was found that phase transition is accompanied by change of conformation of cyclosiloxane moiety from boat-saddle (cradle) to chair. According to PBE0/6-311G(d,p) calculation of isolated D4, such conformation changes are characterized by a low barrier (0.07 kcal/mol). The character of molecular thermal motion and the path of phase transition were established with combination of periodic DFT calculations, including molecular dynamics and metadynamics. The effect of crystal field led to an increase in the calculated phase transition barrier (4.27 kcal/mol from low- to high-temperature phase and 3.20 kcal/mol in opposite direction).

Synthesis, characterization and evaluation of azobenzene nanogels for their antibacterial properties in adhesive dentistry

The presence of cariogenic bacteria within the prepared tooth cavity at the adhesive resin-dentin interface is detrimental to the long-term stability and function of composite restorations. Here, we report the synthesis and incorporation of methacrylated azobenzene nanogels within bisphenol A-glycidyl methacrylate/hydroxyethyl methacrylate/ethanol (B/H/E) adhesive resins and evaluate their ability to reduce the bacterial invasion of cariogenic Streptococcus mutans biofilms while preserving the mechanical strength and structural integrity of the critical interfacial connection between the restoration and the tooth. The azobenzene nanogel, with a hydrodynamic radius of < 2 nm and a molecular weight of 12,000 Da, was polymerized within B/H/E adhesive formulations at concentrations of 0.5 wt.%, 1.5 wt.%, and 2.5 wt.%. While the double-bond conversion, cytocompatibility, water solubility, and sorption of the adhesive networks were comparable, azobenzene nanogel networks showed improved hydrophobicity with a ≥ 25° increase in water contact angle. The polymerized adhesive surfaces formulated with azobenzene nanogels showed a 66% reduction in bacterial biofilms relative to the control while maintaining the mechanical properties and micro-tensile bond strength of the adhesive networks. The increased hydrophobicity and antibacterial activity are promising indicators that azobenzene nanogel additives have the potential to increase the durability and longevity of adhesive resins.

Nanogel-Facilitated In-Situ Delivery of a Cataract Inhibitor

Cataracts are a leading cause of blindness worldwide. Surgical removal of cataracts is a safe and effective procedure to restore vision. However, a large number of patients later develop vision loss due to regrowth of lens cells and subsequent degradation of the visual axis leading to visual disability. This postsurgical complication, known as posterior capsular opacification (PCO), occurs in up to 30% of cataract patients and has no clinically proven pharmacological means of prevention. Despite the availability of many compounds capable of preventing early steps in PCO development, there is currently no effective means to deliver such therapies into the eye for a suitable duration. To model a solution to this unmet medical need, we fabricated acrylic substrates as intraocular lens (IOL) mimics scaled to place into the capsular bag of the mouse lens following a mock-cataract surgery. Substrates were coated with a hydrophilic crosslinked acrylate nanogel designed to elute Sorbinil, an aldose reductase inhibitor previously shown to suppress PCO. Insertion of the Sorbinil-eluting device into the lens capsule at the time of cataract surgery resulted in substantial prevention of cellular changes associated with PCO development. This model demonstrates that a cataract inhibitor can be delivered into the postsurgical lens capsule at therapeutic levels.

Intraocular lenses as drug delivery devices

Cataract surgery is one of the most common and safe surgical procedures nowadays. However, it is not free of risks as endophthalmitis, ocular inflammation and posterior capsule opacification (PCO) can appear as post-surgery complications. The usual eye drop therapy used as prophylaxis for the former two complications has limited bioavailability. In turn, the prevention of PCO involves an adequate surgical technique and a careful choice of intraocular lens (IOL) design and material. Also, different drugs have been tested to reduce incidence of PCO, but no prophylaxis demonstrated to be completely effective. In the past few years, IOLs have been proposed as drug delivery devices to replace or/assist the usual eye drop therapy in the post-operatory period. The great advantage of drug loaded IOLs would be to ensure a continuous drug delivery, independent of patient's compliance without requiring any further action besides IOL implantation. The biggest challenge of drug loaded IOLs production is to achieve a controlled and extended release that meet therapeutic needs without inducing toxicity to the surrounding ocular tissues or affecting the physical properties of the lens. This review starts by addressing the possible complications after cataract surgery, as well as the most commonly adopted prophylaxis for each of them. The various types of IOLs are described and their main advantages/disadvantages are discussed. The different strategies pursued to incorporate drugs into the IOLs and control their release, which include soaking the IOL in the drugs solution, supercritical impregnation, surface modifications, and attachment of drug reservoirs to the IOL, among others, are reported. For each strategy, a summary of the publications is presented, which includes the target complication, the types and amounts of released drugs and the IOL materials. A brief description of each individual study is given afterwards. Optimization of drug loaded IOLs through mathematical modelling and possible issues raised by their sterilization are also tackled. At the end, the future commercialization of drug loaded IOLs is commented.

Cell-penetrating peptide CGKRK mediates efficient and widespread targeting of bladder mucosa following focal injury

The bladder presents an attractive target for topical drug delivery. The barrier function of the bladder mucosa (urothelium) presents a penetration challenge for small molecules and nanoparticles. We found that focal mechanical injury of the urothelium greatly enhances the binding and penetration of intravesically-administered cell-penetrating peptide CGKRK (Cys-Gly-Lys-Arg-Lys). Notably, the CGKRK bound to the entire urothelium, and the peptide was able to penetrate into the muscular layer. This phenomenon was not dependent on intravesical bleeding and was not caused by an inflammatory response. CGKRK also efficiently penetrated the urothelium after disruption of the mucosa with ethanol, suggesting that loss of barrier function is a prerequisite for widespread binding and penetration. We further demonstrate that the ability of CGKRK to efficiently bind and penetrate the urothelium can be applied toward mucosal targeting of CGKRK-conjugated nanogels to enable efficient and widespread delivery of a model payload (rhodamine) to the bladder mucosa.

Thiol-functionalized nanogels as reactive plasticizers for crosslinked polymer networks

Significant efforts have been expended to mitigate plasticizer migration from crosslinked methacrylic and poly(vinyl chloride) polymer networks by synthesizing reactive plasticizers that can blend homogenously within the networks to reduce polymer property change, acute toxicity and downstream environmental effects of plasticizer migration with limited and varying amount of success. We hypothesized that appropriate thiol-functionalized nanogels synthesized using the same monomers as the parent network to generate highly compact, crosslinked structures will form thermally stable, homogenous networks and perform as optimal reactive plasticizers. Nanogels were synthesized via a thiol-Michael addition solution polymerization and incorporated at different mass ratios within a polyethylene glycol 400 urethane dimethacrylic monomer to form photo-crosslinked networks. While maintaining the inherent hydrolytic stability, thermal stability and biocompatibility of the parent matrix at ~99% acrylic group conversion, the PEG400 urethane dimethacrylic -nanogel networks retained optical clarity with >90% visible light transmission at 20wt% nanogel concentration within the matrix. The addition of the nanogels also enhanced the elongation of the parent matrix by up to 320%, while a 37°C reduction in glass transition temperature (∆T_g) and ≥50% reduction in modulus was observed. A 52% reduction in the shrinkage stress of the material was also noted. The results indicate that the application of thiol-functionalized nanogels as plasticizers to alter the bulk properties of the parent matrix while mitigating plasticizer migration by covalently crosslinking the nanogels within the polymer matrix provides a simple yet efficient technique to generate network-specific plasticizers with the ability to alter targeted properties within polymers.