The increased use of medical devices combined with the emergence of new multi‐drug‐resistant bacteria has enhanced research on biomaterial‐related infections. Small size of Ag nanoparticles (AgNPs) has already been suggested to show high antibacterial activities. However, small AgNPs tend to aggregate during preparation, resulting in a significant decrease in their antibacterial properties. Three‐dimensional (3D) graphene can be used as a support matrix, for the fixation of precious metal NPs and the maximization of the load. Here, we present a synthetic poly(amino acid), specifically, polyaspartamide modified by ethylenediamine and ethanolamine [PolyAspAm(EDA/EA)], which was mixed with tannic acid and graphene oxide to fabricate an ultralight 3D graphene hybrid aerogel. Transmission electron microscopy (TEM) revealed AgNP loading on the aerogel with the size of less than 50 nm uniformly dispersed, and AgNP loading on the aerogels led to the inhibition of antibacterial cell growth. The measured antibacterial activity, as determined by the inhibition zone and optical density in test, demonstrated that PolyAspAm(EA/EDA)/TA‐GO‐AgNP has a bacteriostatic and bactericidal effect against Staphylococcus aureus and Escherichia coli, thereby suggesting that this 3D polymer graphene composite gel has potential as a novel antibacterial material for a wide range of clinical applications.
High-resolution DOSY (Diffusion-ordered spectroscopy) is a series of 2-dimensional and 3-dimensional NMR techniques based on the differing diffusivity of constituent molecules in the solution state, with which the individual NMR spectrum of each component in a chemical mixture can be observed. All of the DOSY pulse sequences are derived from the spin-echo or stimulated-echo techniques under the effect of PFG (pulsed field gradient). One of the requirements for successful DOSY experiments and data fitting is that PFG must be uniform across the active sample volume. However, PFG, in general, is not uniform across the active sample volume in commercial high-resolution NMR probes and this nonuniformity of PFG is known to produce systematic errors in DOSY experiments. In fact, a strong and uniform gradient field can be realized only in the central region of the gradient coil and the slice-selection technique, widely used in Magnetic Resonance (MR) imaging, can be employed in resolving problems associated with the nonuniformity of PFG. We have developed a slice-selection pulse block, which can be generally applied to any DOSY pulse sequence with proper care of the phase cycling and experimental parameters. We applied the slice-selection technique to LED and BPPLED pulse sequences, which are among the most popular DOSY pulse sequences, and obtained good experimental results for a chemical mixture.
The shell cross-linked micelles composed of tyramine-conjugated 4-arm poly(propylene oxide)–poly(ethylene oxide) was developed as a carrier for controlled drug delivery. The shell cross-linked tyramine-conjugated 4-arm poly(propylene oxide)–poly(ethylene oxide) micelles were prepared by an enzyme-mediated reaction using horseradish peroxidase and hydrogen peroxide. The physicochemical properties, size distribution, morphologies, and thermal properties of the shell cross-linked tyramine-conjugated 4-arm poly(propylene oxide)–poly(ethylene oxide) micelles were characterized to confirm the micelle formation and controllable properties dependent on the concentration of the catalysts. The in vitro cytocompatibility of the micelles was investigated using NIH3T3 fibroblast cells, and the shell cross-linked tyramine-conjugated 4-arm poly(propylene oxide)–poly(ethylene oxide) micelles showed low cytotoxicity. The in vitro hydrophobic drug release behavior from the shell cross-linked tyramine-conjugated 4-arm poly(propylene oxide)–poly(ethylene oxide) micelles was controllable with a sustained release behavior. Therefore, the shell cross-linked tyramine-conjugated 4-arm poly(propylene oxide)–poly(ethylene oxide) micelles via enzyme-mediated reaction have potential as nanocarriers for controlled drug delivery.
In this study, in situ–forming quercetin-conjugated heparin hydrogels to be used to coat metal surfaces for blood compatibility were developed and characterized. Four units of quercetin and poly(ethylene glycol)–tyramine were conjugated per heparin for blood compatibility and hydrogel formation, respectively. The product, quercetin-conjugated heparin–poly(ethylene glycol)–tyramine, was cross-linked in situ via an enzymatic reaction using horseradish peroxidase and hydrogen peroxide to form a hydrogel. The physicochemical properties, such as the gelation time and swelling/degradation time as well as the release kinetics of quercetin, were controlled by changing the catalytic concentrations. The quercetin-conjugated heparin hydrogel, when adhered to a metal surface, enhanced blood compatibility and reduced platelet adhesion by 77%. The release of quercetin inhibited the proliferation of smooth muscle cells. The quercetin-conjugated heparin–poly(ethylene glycol)–tyramine hydrogel is a promising biomaterial with a stable-coated metal surface, with enhanced blood compatibility and antiproliferation effects.
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