Materials and Methods: The formulation design was based on the independent formulation variables of the concentration of chitosan and sodium tripolyphosphate using a simple factorial design experiment. DEET-loaded microparticles were developed and incorporated into a hydrogel. The size of the microparticles was analyzed using the Zetasizer Nano® particle size analyzer, and the surface morphology, using field emission scanning electron microscopy. Drug release from the microparticles was determined by the dialysis bag method. A rheological evaluation of the formulated gel was performed using a Thermo Haake Rheometer. The in vitro permeation of the formulation was performed using a synthetic Strat-M® membrane.
Results: The size of the microparticles ranged from 0.45 to 8.3 μm, and the encapsulation efficiencies were >50% for all the formulations. The drug-release curves showed no initial burst release from the microparticle formulation. Instead, a slow and controlled drug release was observed over 24 hours that followed Higuchi kinetics. The cumulative amount of DEET permeated (over 24 h) from the DEET solution (control), and the formulation was 211.6±19.5 μg/cm2 and 4.07±0.08 μg/cm2, respectively.
Conclusion: A significantly low DEET permeation from the microparticle formulations indicated minimal absorption of the drug into the body and thus, reduced systemic toxicity. Thixotropic evaluation of the hydrogel formulation demonstrated a hysteresis loop that fitted closely to the Herschel-Bulkley rheological model, ensuring an effortless application and prolonged retention on the skin. Hence, it can be concluded that the developed formulation is an effective delivery approach for controlled insect repellent activity with reduced skin absorption.
SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12088-022-01050-9.
MATERIALS AND METHODS: A total of 119 AA patients had been identified from hospital records of the involved sites, namely Queen Elizabeth Hospital in Sabah, Sarawak General Hospital, Sibu Hospital, Miri Hospital and Bintulu Hospital in Sarawak from Jan 2006 to Dec 2017.
RESULTS: The median age at diagnosis was 46 years, and native ethnic group from Sabah, Kadazan-Dusun, recorded the highest percentage of 41.2%, which could be explained by higher frequency of HLA-DRB1*15:01, an alelle linked to increased risk of AA, among this ethnic group. The majority of patients (59.7%) received cyclosporine (CsA) as monotherapy or in combination with other non-IST agents such as danazol, which was instituted in 48.7% of the patients, while a third of them (33.7%) received antithymocyte globulin (ATG) therapy with or without CsA, and 12.4% underwent allogenic SCT. The five-year overall survival (OS) for all AA patients was 76.1%. Elderly patients >60 years old and those with severe disease had more inferior 5-year survival.
CONCLUSION: A prospective study is warranted to determine the true incidence rate, epidemiological distributions, treatment outcome and overall survival of AA patients in Malaysia. Establishment of allogenic SCT in East Malaysia is imperative to make this curative therapy more accessible to patients with severe disease and improve the outcome.