Abstract
In the present study, optimized binary lipid matrices of Tallow fat- Transcutol and Precirol-Transcutol were used to formulate sustained release solid lipid nanoparticles loaded lumefantrine and ciprofloxacin. The homolipid (tallow fat from Bos indicus was extracted and purified following standard methods. Abinitio selection of lipid matrices was done by formulation of binary (3:1) and ternary lipid matrices with different ratios, (1:1:1, 1:2:2 and 2:1:1). Single, binary and ternary lipid matrices were characterized by differential scanning calorimetry (DSC) after which the binary lipid matrices of Precirol- Transcutol and Tallow fat- Transcutol of 3:1 ratio with the least enthalpy were optimized. The optimized lipid matrices were the employed to prepare solid lipid nanoparticles using Poloxamer 188 (2%), Tween 80 (1%) and Solutol HS (3%) as the surfactants by the hot homogenization technique. The following parameters were evaluated on the formulated solid lipid nanoparticles (SLN) – thermal properties, particle size, zeta potential, polydispersity index, particle morphology, encapsulation efficiency ,compatibility/interaction study using FT-IR and in vitro drug release as well as in vivo release using animal model. Solid lipid nanoparticle (SLN)- loaded lumefantrine was directly compressed with artemether to form liquisolid tablets/compacts which were characterized as by weight uniformity, hardness, friability and disintegration time tests. In-vitro release study was performed in simulated gastric fluid (SGF) of pH 1.2 and simulated Intestine fluid (SIF) of pH 7.2 and release data were fitted into zero order, first order, Higuchi and Ritger-Peppas mathematical release models to determine kinetics and mechanism of release. Peter’s 4-day days curative test was carried out in mice with liquisolid compacts lumefantrine –artemether tablets using a chloroquine-sensitive strain of Plasmodium berghei berghei. In-vitro antimicrobial activity was carried out on SLN loaded ciprofloxacin. xiii The DSC results for the single lipid showed melting peaks at 71.00 C, 130.30 C, 56.40 C and 130.80 C for Precirol®, Transcutol®, Tallow fat and P90G® respectively with a corresponding enthalpies of –37.59mW/mg, –26.76mW/mg,–27.84mW/mg and – 25.98mW/mg respectively. High melting peaks and enthalpies was observed here. The DSC results for the binary lipid matrices showed melting peaks at 59.70 C, 60.30 C, 56.50 C, 57.50 C for Precirol®– Transcutol®, Precirol®–P90G®, Tallow fat– Transcutol® and Tallow fat– P90G® respectively with a corresponding enthalpies of –14.15mW/mg, –20.27mW/mg, – 22.31mW/mg and – 28mW/mg .There was marked reduction in both melting peaks and enthalpies. Ternary lipid matrices showed DSC results of melting peaks at 59.10 C, 54.00 C and 62.30 C for Precirol®– Tallow fat– Transcutol®(1:1:1), Precirol®– Tallow fat– Transcutol®(1:2:2) and Precirol®– Tallow fat– Transcutol®(2:1:1) with corresponding enthalpies of – 34.66mW/mg,–23.33mW/mg and –30.55mW/mg respectively .Reduction in melting peaks and increased enthalpies was observed here. From the above DSC results of single, binary and ternary lipid matrices, two binary lipid matrices with the least melting peaks and enthalpies were optimized and employed in the formulation of solid lipid nanoparticles (SLN). Optimized binary lipid matrices were Precirol®- Transcutol® lipid matrix with melting peak at 59.70 C with an enthalpy of–14.15mW/mg( Batch A) and Tallow fat– Transcutol® lipid matrix with melting peak at 56.50 C with an enthalpy of – 22.31mW/mg ( Batch B). Formulated SLNs were yellow and white in colour respectively which represents lumefantrine and ciprofloxacin batches. Liquisolid compacts (lumefantrine –artemether tablets) appeared light yellow in colour. Percentage yield of SLN was generally high especially for the batch A (Precirol® –Transcutol® lipid matrix) samples which were in the range of (58.8% to 91.9%) over batch B (Tallow fat –Transcutol® lipid matrix) samples which were in the range of (44.1% to 86.2%). Scanning electron microscope (SEM) showed xiv that the SLNs were well formed, smooth, spherically shaped and non-porus. Nanoparticles size of SLN was in the range of 570.3±2.1 to 930.2±2.2 for SLNs prepared with Precirol®- Transcutol® matrics and 655.9±2.0 to 896.9±0.1 for SLN prepared with Tallow fatTranscutol matrics . Zeta potential was in the range of -24.8±1.2 to –29.2±0.1. Polydispersity index was in the range of 0.58 to 0.88. Drug –loading increased the size of SLN. Time dependent pH stability studies showed that the formulated SLN had an acidic pH within the range of (4.0 to 6.2), and minimal increase in acidity in all batches was also observed after 3 and 6 months of storage. Encapsulation efficiencies was high (70.1 -94.8). DSC results for batch A (Precirol®- Transcutol® matrics) had melting peaks in the range of (56.40 C to 155.60 C) with corresponding enthalpies in the range of (–10.92mW/mg to – 37.59mW/mg ) while batch B (Tallow fat- Transcutol® matrics) had melting peaks in the range of (53.40 C to 1300 C) with corresponding enthalpies in the range of (–23.87mW/mg to –42.56mW/mg ). Following the performance of SLNs from the above characterization , four batch samples were optimized out of total of twenty (20) SLN samples formulated, optimized samples from batch A (Precirol®- Transcutol® matrics) was AL4 (which contain 0.8 w/w % of lumefantrine) and AC5 (which contain 1 w/w% of ciprofloxacin). Optimized samples from batch B (Tallow fat- Transcutol matrics) was BL3 (which contain 0.5 w/w % of lumefantrine) BC5 (which contain 1 w/w% of ciprofloxacin). Optimized samples of lumefantrine -loaded SLN from both batches was then formulated into liquisolid compact formulations. Average weight uniformity was in the range of (370±1.0 to 400±0.01) ,thickness (4.0±2.1 to 4.3±1.3), friability (0.51±1.0 to 1.4±1.2), average hardness 0.5±2.2 to 1.4±2.2) and disintegration time (3.10 to 25.30). Antmicrobial activity of SLN loaded ciprofloxacin for batch A (Precirol®- Transcutol® matrics) that contain 1 w/w% of ciprofloxacin (AC5) showed inhibition zone diameter of 23.7mm at concentration of xv 2.2µg/ml against commercial sample that showed inhibition zone diameter of 23.3mm at concentration of 7.5µg/ml and pure sample showed IZD of 18mm at concentration of 1.87µg/ml while AC5 showed IZD of 22mm at concentration of 1.2µg/ml. For batch B, BC5 (Tallow fat- Transcutol® matrics with 1% w/w of ciprofloxacin) showed IZD of 22.7mm at concentration of 3.25µg/ml against the pure sample which showed IZD of 18.3mm at concentration of 3.25µg/ml and 17.3mm at concentration of 2.2µg/ml against commercial brand which showed 17mm of IZD at 3.75µg/ml. In-vitro release studies carried out on SLNs loaded ciprofloxacin showed highest release in SIF (98.4%) after 24h for the batch B formulated with Tallow fat- Transcutol matrices . There was general high release also in all batches in SGF (66.12% to 80%). Liquisolid compact of lumefantrine-artemether tablets showed highest sustained release of lumefantrine in SIF (84.32%) for batch A (Precirol®- Transcutol® matrics) followed by batch B (Tallow fat- Transcutol matrics ) which had 77.9%. SGF release profile of lumefantrine were in the range of (61.4% to 71.8%), release of artemether showed increased release in SIF (89%) than SGF. Release of drugs (lumefantrine and artemether) was significantly higher (p
