Fabrication of nanocrystal forms of á´ -cycloserine and their application for transdermal and enteric drug delivery systems.

ᴅ-cycloserine (DCS), an FDA-approved medicine for the treatment of tuberculosis, is also a partial agonist at the glycine recognition site of N-methyl-ᴅ-aspartate (NMDA) receptor and has shown significant treatment efficacy for central nervous system (CNS) disorders including depression, schizophrenia, Alzheimer's disease, and post-traumatic stress disorder. The physicochemical properties of DCS, however, limit the options of formulation and medicinal applications of DCS, and warrants further investigation for the development of CNS therapeutics. Nanocrystals play an important role in pharmaceutic design and development. The properties of nanocrystals are remarkably different from their bulk material counterpart, attributed to the large surface-area-to-volume ratio which can improve the bioavailability. In this study, for the first time, DCS, a highly water-soluble compound, has formed nanocrystals and this was confirmed by scanning electronic microscopy and X-ray powder diffraction. Furthermore, DCS nanocrystals were applied to several formulations to test their stability and then to the in vitro Franz diffusion test with reservoir patch formulation as well as in vivo pharmacokinetics study with enteric capsules. We tested these formulations regarding their nanocrystal physical properties, size effect, and dissolution rate, respectively. We found that DCS nanocrystals showed good performance in the Franz diffusion test and rodent pharmacokinetic studies due to the nanoparticle size and faster dissolution as compared with the commercial DCS powder. These DCS nanocrystal formulations could offer a new approach for the development of an advanced drug delivery system for the treatment of CNS disorders.

The Development of a Regulator of Human Serine Racemase for N-Methyl-D-aspartate Function.

It is crucial to regulate N-methyl-D-aspartate (NMDA) function bivalently depending on the central nervous system (CNS) conditions. CNS disorders with NMDA hyperfunction are involved in the pathogenesis of neurotoxic and/or neurodegenerative disorders with elevated D-serine, one of the NMDA receptor co-agonists. On the contrary, NMDA-enhancing agents have been demonstrated to improve psychotic symptoms and cognition in CNS disorders with NMDA hypofunction. Serine racemase (SR), the enzyme regulating both D- and L-serine levels through both racemization (catalysis from L-serine to D-serine) and ß-elimination (degradation of both D- and L-serine), emerges as a promising target for bidirectional regulation of NMDA function. In this study, we explored using dimethyl malonate (DMM), a pro-drug of the SR inhibitor malonate, to modulate NMDA activity in C57BL/6J male mice via intravenous administration. Unexpectedly, 400 mg/kg DMM significantly elevated, rather than decreased (as a racemization inhibitor), D-serine levels in the cerebral cortex and plasma. This outcome prompted us to investigate the regulatory effects of dodecagalloyl-α-D-xylose (α12G), a synthesized tannic acid analog, on SR activity. Our findings showed that α12G enhanced the racemization activity of human SR by about 8-fold. The simulated and fluorescent assay of binding affinity suggested a noncooperative binding close to the catalytic residues, Lys56 and Ser84. Moreover, α12G treatment can improve behaviors associated with major CNS disorders with NMDA hypofunction including hyperactivity, prepulse inhibition deficit, and memory impairment in animal models of positive symptoms and cognitive impairment of psychosis. In sum, our findings suggested α12G is a potential therapeutic for treating CNS disorders with NMDA hypofunction.

Acidic Microenvironment-Sensitive Core-Shell Microcubes: The Self-assembled and the Therapeutic Effects for Caries Prevention.

OBJECTIVES: The aim of this study was to develop a new material with integrated interface design that could achieve the purpose of environmental-sensing controlled release against cariogenic bacteria. Furthermore, this material can rebalance oral flora and serve as a preventive and reparative measure of dental caries. MATERIALS AND METHODS: NaF@PAA@HA@polyelectrolytes@HA@PAA particles were synthesized using the method of two-solution phases precipitation followed by biocompatible polymers coating layer by layer. The structure of the particles was confirmed by transmission electron microscope. The fluoride release profile was measured by fluoride ion electrode. Antimicrobial activity against the cariogenic microorganisms was analyzed by scanning electron microscopy and energy dispersive spectrum. The efficacy experiments were conducted on tooth enamel slides to evaluated fluoride absorption and antibacterial activity of the prototype toothpaste containing microcube particles RESULTS: The structure of NaF@PAA@HA@polyelectrolytes@HA@PAA particles showed a core surrounded by tooth-adhesion polymer layers in thin fin or filament structure. The loaded concentration of fluoride in the particles' core was 148,996 ± 28,484 ppm. NaF@PAA@HA@polyelectrolytes@HA@PAA particles showed selective inhibition of cariogenic microorganisms over probiotic strains and stronger fluoride adhesion on tooth enamel. A burst release (over 80%) of fluoride from the particle-containing toothpaste was observed under cariogenic acidic environment (pH < 5), while it remained extremely low under neutral environment. Compared with the best results of commercial toothpastes, our prototype toothpaste increased enamel fluoride uptake by 8-fold in normal enamel slides and by 11-fold in the slides with induced white spot lesions after either 1- or 7-day treatment. The prototype toothpaste also showed better inhibition of cariogenic microorganisms than the commercial brands. The coverage area of cariogenic bacteria under our toothpaste treatment was 73% on normal enamel slides compared with the commercial brands, while it was 69% in the induced white spot lesions. CONCLUSIONS: In our study, an intelligent toothpaste was developed that selectively inhibits cariogenic bacteria by microenvironment proton-triggered fluoride release. Such novel design would accomplish a favorable flora balance for optimal long-term oral health.

Development of Ultrapure and Potent Tannic Acids as a Pan-coronal Antiviral Therapeutic.

The rampageous transmission of SARS-CoV-2 has been devastatingly impacting human life and public health since late 2019. The waves of pandemic events caused by distinct coronaviruses at present and over the past decades have prompted the need to develop broad-spectrum antiviral drugs against them. In this study, our Pentarlandir ultrapure and potent tannic acids (UPPTA) showed activities against two coronaviral strains, SARS-CoV-2 and HCoV-OC43, the earliest-known coronaviruses. The mode of inhibition of Pentarlandir UPPTA is likely to act on 3-chymotrypsin-like protease (3CLpro) to prevent viral replication, as supported by results of biochemical analysis, a 3CLpro assay, and a "gain-of-function" 3CLpro overexpressed cell-based method. Even in the 3CLpro overexpressed environment, Pentarlandir UPPTA remained its antiviral characteristic. Utilizing cell-based virucidal and cytotoxicity assays, the 50% effective concentrations (EC50) and 50% cytotoxicity concentration (CC50) of Pentarlandir UPPTA were determined to be ∼0.5 and 52.5 µM against SARS-CoV-2, while they were 1.3 and 205.9 µM against HCoV-OC43, respectively. In the pharmacokinetic studies, Pentarlandir UPPTA was distributable at a high level to the lung tissue with no accumulation in the body, although the distribution was affected by the food effect. With further investigation in toxicology, Pentarlandir UPPTA demonstrated an overall safe toxicology profile. Taking these findings together, Pentarlandir UPPTA is considered to be a safe and efficacious pancoronal antiviral drug candidate that has been advanced to clinical development.

Octahedron Iron Oxide Nanocrystals Prohibited Clostridium difficile Spore Germination and Attenuated Local and Systemic Inflammation.

Clinical management of Clostridium difficile infection is still far from satisfactory as bacterial spores are resistant to many chemical agents and physical treatments. Certain types of nanoparticles have been demonstrated to exhibit anti-microbial efficacy even in multi-drug resistance bacteria. However, most of these studies failed to show biocompatibility to the mammalian host cells and no study has revealed in vivo efficacy in C. difficile infection animal models. The spores treated with 500 µg/mL Fe3-δO4 nanoparticles for 20 minutes, 64% of the spores were inhibited from transforming into vegetative cells, which was close to the results of the sodium hypochlorite-treated positive control. By cryo-electron micro-tomography, we demonstrated that Fe3-δO4 nanoparticles bind on spore surfaces and reduce the dipicolinic acid (DPA) released by the spores. In a C. difficile infection animal model, the inflammatory level triple decreased in mice with colonic C. difficile spores treated with Fe3-δO4 nanoparticles. Histopathological analysis showed a decreased intense neutrophil accumulation in the colon tissue of the Fe3-δO4 nanoparticle-treated mice. Fe3-δO4 nanoparticles, which had no influence on gut microbiota and apparent side effects in vivo, were efficacious inhibitors of C. difficile spore germination by attacking its surface and might become clinically feasible for prophylaxis and therapy.