Sustained Release Solid Lipid Nanoparticles Formulation of Lumefantrine and Ciprofloxacin

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. The DSC results for the single lipid showed melting peaks at 71.00C, 130.30C, 56.40C and 130.80C 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 59.70C, 60.30C, 56.50C, 57.50C 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 59.10C, 54.00C and 62.30C 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 59.70C with an enthalpy of–14.15mW/mg( Batch A) and Tallow fat– Transcutol® lipid matrix with melting peak at 56.50C 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 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 fat- Transcutol 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 (56.40C to 155.60C) 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 (53.40C to 1300C) 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 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<0.05) from liquisolid compact of lumefantrine –artemether. Release of ciprofloxacin from SLNs in batch A, AC5 (Precirol®- Transcutol® matrices) were in the range of (5.2% to 97.7%) for SGF while SIF release was in the range of (3.5% to 66.12%). Release profile of ciprofloxacin from SLNs in batch B, BC5 (Tallow fat- Transcutol® matrics) were in the range of (6.8% to85.7%) for SGF whereas release in SIF was in the range (4.2% to 98.4%). Evaluation of the kinetics of release for all the batches showed mixed zero order and Higuchi release patterns in all media (SGF & SIF). In terms of mechanism of drug release, anomalous or non-Fickian diffusion and super case II transport were the major mechanism of drug release from SLNs for ciprofloxacin and lumefantrine and artemether from liquisolid compacts formulations. The FT-IR spectra for the lipid matrices showed similar characteristics peaks as those observed for Precirol, Transcutol and Tallow fat indicating that there was no adverse interaction between Precirol®-Transcutol® and Tallow fat- Transcutol .Comparing the FTIR spectra of all batches of SLNs alongside the pure drug samples showed that the major peaks were maintained. The result obtained in the in vivo schizontocidal activity, indicated that the administration of liquisolid compact (lumefantrine –artemether tablets) resulted in significant decrease in parasitaemia (p<0.05) in the treated groups, higher than in non-treated group. Also the calculated activity was higher in all groups that received formulated tablets than in the commercial sample. Highest activity was achieved with batch AL4-1 (batch A,Precirol®- Transcutol® matrics which contain 0.8 w/w % of lumefantrine) and BL3-1 (batch B, Tallow fat- Transcutol matrics which contain 0.5 w/w % of lumefantrine ) liquisolid compact tablets. Liquisolid compacts (tablets) produced from formulated SLNs showed superior sustained parasitaemia reduction than convectional frequently-dosed regimen. This was supported by the small-sized nanometer particles with high %EE, stability and low crystallinity due to the liquid oil core that solubilized the drug. On the other hand, the ciprofloxacin-loaded nanoparticles had superior antibacterial activity on B. substlis, than Ciprotab®. This shows that SLNs can conveniently improve compliance to the studied drugs due to improved activity, reduced dosing frequency and associated side effects.