Wesley Nyaigoti Omwoyo

Preparation, characterization, and optimization of primaquine-loaded solid lipid nanoparticles

Primaquine (PQ) is one of the most widely used antimalarial drugs and is the only available drug that combats the relapsing form of malaria. PQ use in higher doses is limited by severe tissue toxicity including hematological- and gastrointestinal-related side effects. Nanoformulation of drugs in an appropriate drug carrier system has been extensively studied and shown to have the potential to improve bioavailability, thereby enhancing activity, reducing dose frequency, and subsequently reducing toxicity. The aim of this work was to design, synthesize, and characterize PQ-loaded solid lipid nanoparticles (SLNs) (PQ-SLNs) as a potential drug-delivery system. SLNs were prepared by a modified solvent emulsification evaporation method based on a water-in-oil-in-water (w/o/w) double emulsion. The mean particle size, zeta potential, drug loading, and encapsulation efficiency of the PQ-SLNs were 236 nm, +23 mV, 14%, and 75%, respectively. The zeta potential of the SLNs changed dramatically, from −6.54 mV to +23.0 mV, by binding positively charged chitosan as surface modifier. A spherical morphology of PQ-SLNs was seen by scanning electron microscope. In vitro, release profile depicted a steady drug release over 72 hours. Differential scanning calorimeter thermograms demonstrated presence of drug in drug-loaded nanoparticles along with disappearance of decomposition exotherms, suggesting increased physical stability of drug in prepared formulations. Negligible changes in characteristic peaks of drug in Fourier transform infrared spectra indicated absence of any interaction among the various components entrapped in the nanoparticle formulation. The nanoformulated PQ was 20% more effective as compared with conventional oral dose when tested in Plasmodium berghei-infected Swiss albino mice. This study demonstrated an efficient method of forming a nanomedicine delivery system for antimalarial drugs.

Development, characterization and antimalarial efficacy of dihydroartemisinin loaded solid lipid nanoparticles

UNLABELLED Effective use of dihydroartemisinin (DHA) is limited by poor water-solubility, poor pharmacokinetic profile and unsatisfactory clinical outcome especially in monotherapy. To reduce such limitations, we reformulated DHA into solid lipid nanoparticles (SLNs) as a nanomedicine drug delivery system. DHA-SLNs were characterized for physical parameters and evaluated for in vitro and in vivo antimalarial efficacy. DHA-SLNs showed desirable particle characteristics including particle size (240.7 nm), particle surface charge (+17.0 mV), drug loadings (13.9 wt %), encapsulation efficacy (62.3%), polydispersity index (0.16) and a spherical appearance. Storage stability up to 90 days and sustained release of drug over 20 h was achieved. Enhanced in vitro (IC50 0.25 ng/ml) and in vivo (97.24% chemosuppression at 2mg/kg/day) antimalarial activity was observed. Enhancement in efficacy was 24% when compared to free DHA. These encouraging results show potential of using the described formulation for DHA drug delivery for clinical application. FROM THE CLINICAL EDITOR Malaria still poses a significant problem worldwide. One of the current drugs, artemisinin has been shown to be effective, but has poor water-solubility. The authors here described their formulation of making dihydroartemisinin (DHA) into solid lipid nanoparticles, with subsequent enhancement in efficacy. These results would have massive potential in the clinical setting.

Effects of Micronutrients on the Nutritional Status of Clonal Tea Replanted in Areas Where Old Tea Was Uprooted

Tea yields peak is 21-30 years after which yields decline. The declining productivity and moribuncy has been reported in many tea fields due to prolonged period of monoculture under tea, physicochemical and biological properties of soil deteriorate considerably causing diseases, pests, acidic soils among others which leads to uprooting of old tea bushes. Deficiency of micronutrients in some tea sections has been reported which has been corrected by foliar application. Though the deficiency could be corrected through foliar application, this mode of application has its shortcomings including leaf burn and the mobility of nutrients from the leaves to the roots is very slow. This study aimed at determining the effect of soil application and variation of micronutrients on the nutritional status of clonal tea replanted in old tea lands.Leaf and soil samples were collected in a random complete block design and the micromutrient levels determined using Inductively Coupled Plasma Emission (ICPE). Data analysis was done using MSTAT-C software.The changes in the levels of micronutrients with varied eight micronutrient combinations subjected on different clones were studied. Clone 12/28 significantly (P≤0.05) varied with the other clones indicating that different clones have varied abilities to absorb nutrients. Clone 303/577 gave a significantly higher uptake of B in the order TRFK303/577 >S15/10 >12/28 >31/8. Clone 12/28 recorded a higher uptake of N with mean levels of 3.075, clone 31/8 had significantly higher uptakes of Fe and Zn. None of the micronutrients subjected on the clones brought an impact in the uptake of N and Mg. This study therefore recommends the use of soil application of micronutrients as an alternative to foliar application in areas where old tea bushes were uprooted.

Development and Validation of a GC-MS Method for the Quantitation of Nanoformulated Primaquine in Whole Blood and Plasma of Mouse Model

AGaschromatography-massspectrometry(GC/MS)methodwasdevelopedandvalidatedforthe quantitationoftheantimalarialdrug,nanoformulatedPrimaquine(PQ),inwholebloodandplasma. Theanalytewasextractedusingaproteinprecipitationmethodfollowedbychromatographicseparation onaWatersXterra,RPC8,2.5μm,50mmx4.6mmanalyticalcolumnwithamobilephaseconsisting ofA:0.5%Formicacidin20mMNH4COOH,B:MethanolpHadjustedto3.0withFAataratio of3:7(v/v),deliveredataconstantflowrateof0.5ml/min.Mefloquine(MEF)wasusedasthe internalstandard.Compoundreactionmonitoringwasperformedusing260.4Daforprecursorion and175.2and379.2DaforproductionsforthequantificationofPQand379.2Daforprecursorion and175.2and379.2Daforproductionsforthequantification,respectively.Calibrationcurveswere constructedovertheconcentrationrange16.7–4300ng/ml.Themeanintra-andinter-assayaccuracy valuesfortheanalysisofPQinWBwas104%(%CV=5.6)and98.6%(%CV=5.7),respectively. Themeanintra-andinter-assayaccuracyvaluesfortheanalysisofPQinplasmawas92.7%(%CV =3.7)and93.7%(%CV=5.4),respectively.Nosignificantmatrixeffectwasobservedduringthe methodvalidation.Thevalidatedmethodwasappliedtoanabsorptionstudyinmice,todetermine andcomparePQconcentrationsinwholebloodandplasmasamples.Resultsofthestatisticalanalysis usingalinearmixedeffectsgrowthcurvemodelconcludedthattherewasnosignificantdifference (p-value=0.688)betweenWBandplasmaPQconcentrations.Thismethodutilizesasmallsample volumeof20μl,facilitatinglowbloodcollectionvolumesandashortchromatographicruntimeof 3minwhichallowsforhighsamplethroughputanalysis. KeyWoRDS Mefloquine, Nanoformulated Primaquine, Plasma, Whole Blood