RESUMO
The outbreak of the COVID-19 pandemic in 2019 has been one of the greatest challenges modern medicine and science has ever faced. It has affected millions of people around the world and altered human life and activities as we once knew. The high prevalence as well as an extended period of incubations which usually does not present with symptoms have played a formidable role in the transmission and infection of millions. A lot of research has been carried out on developing suitable treatment and effective preventive measures for the control of the pandemic. Preventive strategies which include social distancing, use of masks, washing of hands, and contact tracing have been effective in slowing the spread of the virus; however, the infectious nature of the SARS-COV-2 has made these strategies unable to eradicate its spread. In addition, the continuous increase in the number of cases and death, as well as the appearance of several variants of the virus, has necessitated the development of effective and safe vaccines in a bid to ensure that human activities can return to normalcy. Nanotechnology has been of great benefit in the design of vaccines as nano-sized materials have been known to aid the safe and effective delivery of antigens as well as serve as suitable adjuvants to potentiate responses to vaccines. There are only four vaccine candidates currently approved for use in humans while many other candidates are at various levels of development. This review seeks to provide updated information on the current nano-technological strategies employed in the development of COVID-19 vaccines.
RESUMO
The present study aimed to develop low-dose liquisolid tablets of two antimalarial drugs artemether-lumefantrine (AL) from a nanostructured lipid carrier (NLC) of lumefantrine (LUM) and estimate the potential of AL as an oral delivery system in malariogenic Wistar mice. LUM-NLCs were prepared by hot homogenization using Precirol® ATO 5/Transcutol® HP and tallow fat/Transcutol® HP optimized systems containing 3:1 ratios of the lipids, respectively, as the matrices. LUM-NLC characteristics, including morphology, particle size, zeta potential, encapsulation efficiency, yield, pH-dependent stability, and interaction studies, were investigated. Optimized LUM-NLCs were mixed with artemether powder and other dry ingredients and the resultant powder evaluated for micromeritics. Subsequent AL liquisolid tablets were tested for in vitro drug release and in vivo antiplasmodial activity in mice infected with Plasmodium berghei berghei (NK 65). Results showed that optimized LUM-NLC were stable, spherical, polydispersed but nanometric. Percentage yield and encapsulation efficiency were ~92% and 93% for Precirol® ATO 5/Transcutol® HP batch, then 81% and 95% for tallow fat/Transcutol® HP batch while LUM was amorphous in NLC matrix. In vitro AL release from liquisolid compacts revealed initial burst release and subsequent sustained release. Liquisolid tablet compacts formulated with Precirol® ATO 5/Transcutol® HP-AL4 achieved higher LUM release in simulated intestinal fluid (84.32%) than tallow fat/Transcutol® HP-BL3 (77.9%). Non-Fickian (anomalous) diffusion and super case II transport were the predominant mechanisms of drug release. Equal parasitemia reduction was observed for both batches of tablet compacts (~92%), superior to the reduction obtained with commercial antimalarial formulations: Coartem® tablets (86%) and chloroquine phosphate tablets (66%). No significant difference (P<0.05) in parasite reduction between double (4/24 mg/kg) and single (2/12 mg/kg) strength doses of AL compacts was observed. Our result highlights that AL could be formulated in much lower doses (4/24 mg/kg), for once-in-two days oral administration to improve patient compliance, which is currently not obtainable with conventional AL dosage forms.