Browsing by Author "Oloo, Florence"

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Development, characterization and antimalarial efficacy of dihydroartemisinin loaded solid lipid nanoparticles.
(Elsevier, 2016-04-01) Omwoyo, Wesley; Melariri, Paula; Gathirwa, Jeremiah; Oloo, Florence; Mahanga, Geoffrey; Kalombo, Lonji; Ogutu, Bernhards; Swai, Hulda
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 2 mg/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.
Nanoformulation and Preclinical Evaluation of Dihydroartemisinin–Lumefantrine and Primaquine as Combined Antimalarial Therapy
(John Wiley and Sons Ltd, 2025-05-12) Odera, Pesila; Otieno, Geoffrey; Onyango, Joab; Ogutu, Bernhards; Owour, James; Oloo, Florence; Ongas, Martin; Swai, Hulda; Gathirwa, Jeremiah
The World Health Organization recommends artemisinin-based combinations for uncomplicated malaria treatment. Artemether and lumefantrine (LUM) are the first-line treatments, with artemether serving as a prodrug of dihydroartemisinin (DHA), while primaquine (PQ) is primarily used as a prophylactic drug. However, these drugs face challenges such as toxicity, low bioavailability, and poor aqueous solubility. The advent of nanomedicine offers solutions by improving drug pharmacokinetic and pharmacodynamic profiles, thereby enhancing therapeutic efficacy. This study aimed to improve the efficacy of DHA, LUM, and PQ through nanoformulation using solid lipid nanoparticles (SLNs). These nanoparticles were prepared using a modified solvent extraction method based on a water-in-oil-in-water (W/O/W) double emulsion. The resulting nanoparticles had a mean particle size of 357.1 ± 57.14 nm, a polydispersity index of 0.657 ± 0.091, and a zeta potential of −35.7 ± 1.25 mV. The encapsulation efficiencies of DHA, LUM, and PQ were 93.98 ± 0.41%, 42.03 ± 9.46%, and 87.60 ± 0.64%, respectively, with drug loading capacities of 11.87 ± 0.04%, 24.10 ± 2.88%, and 8.01 ± 0.09%. The drugs followed Kors–Peppas and Higuchi drug release models and were released progressively over 68 h. The nanoparticles were spherically shaped, and Fourier transform infrared (FTIR) spectroscopy confirmed the successful nanoformulation process. The nanoformulated drugs demonstrated 30% greater efficacy than conventional oral doses in clearing Plasmodium berghei infection in Swiss albino mice.
Preparation, characterization, and optimization of primaquine-loaded solid lipid nanoparticles
(Dovepress, 2014-08-11) Omwoyo, Wesley; Ogutu, Bernhards; Oloo, Florence; Swai, Hulda; Kalombo, Lonji; Melariri, Paula; Mahanga, Geoffrey; Gathirwa, Jeremiah
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.