Synthesis, characterization, and in vitro release of oxytetracycline loaded in pH-responsive CaCO3 nanoparticles

Alternative drug delivery for the treatment of resistant bacterial infections is necessary to bypass existing antibioticresistance mechanism and ensure direct delivery of the drug to the targeted site using locally sourced materialsto minimize cost in the long term. In this study, cockle shell-derived calcium carbonate aragonite nanoparticles(CS-CaCO3NP) was synthesized, loaded with oxytetracycline (OTC), and characterized using Zeta analysis,Transmission electron microscopy (TEM), FESEM, X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) andBrunauer–Emmett–Teller analysis. The loaded OTC-CS-CaCO3NP was further characterized after which the in vitrorelease of OTC was studied. A homogenously spherical CS-CaCO3NP was observed on TEM with a mean diameter of29.90 nm and −19.9 zeta potential which increased to 62.40 nm and −23.5, respectively, after OTC loading. XRD andFTIR analysis of OTC-CS-CaCO3NP revealed that OTC maintained its functionality and crystallinity. The formulationof OTC:CS-CaCO3NP in ratio 1:4 with drug encapsulating efficiency (71%) was used for in vitro release studies.OTC was sustainably released from OTC-CS-CaCO3NP over a period of 96 hours. Our results suggest that OTC-CSCaCO3NP is a promising nanoparticle antibiotic delivery system with efficient physicochemical and pharmacologicalproperties whose antibiotic properties should be further investigated.

Possible mechanisms of antinociception of methanol extract of Melastoma malabathricum leaves

ABSTRACT Melastoma malabathricum L., Melastomaceae, has been traditionally used to relieve diverse pain-related ailments. The objectives of the present study were to determine the antinociceptive activity of methanol extract of M. malabathricum leaves and to elucidate the possible mechanisms of antinociception involved using various rats' models. The extract (100, 250, and 500 mg/kg) was administered orally 60 min prior to subjection to the respective test. The in vivo acetic acid-induced abdominal constriction, formalin-induced paw licking, and hot plate tests were used as the models of nociception to evaluate the extract antinociceptive activity. Further studies were carried out to determine the role of opioid and vanilloid receptors, glutamate system and nitric oxide/cyclic guanosine phosphate (NO/cGMP) pathway in modulating the extract antinociceptive activity. From the results obtained, M. malabathricum exhibited significant (p < 0.05) antinociceptive activity in all the chemical- and thermal-induced nociception models. Naloxone (5 mg/kg), a non-selective opioid antagonist, failed to significantly affect the antinociceptive activity of MEMM when assessed using the abdominal constriction-, hot plate- and formalin-induced paw licking-test. M. malabathricum also significantly (p < 0.05) reversed the nociceptive response in capsaicin- and glutamate-induced paw licking test. Furthermore, only L-arginine (a nitric oxide precursor) alone, but not, NG-nitro-L-arginine methyl esters (L-NAME; an inhibitor of NO synthase), methylene blue (MB; an inhibitor of cGMP), or their combination thereof, significantly (p < 0.05) block the antinociceptive activity of M. malabathricum. In conclusion, M. malabathricum exerted a non-opioid antinociceptive activity at the central and peripheral levels partly via the inhibition of vanilloid receptors and glutamatergic system, and activation of the NO-mediated/cGMP-independent pathway.