No description available.

No description available.

The properties of Caco-2 monolayers were compared on aluminium oxide and nitrocellulose permeable-supports. On nitrocellulose, Caco-2 cells displayed a higher rate of taurocholic acid transport than those cultured on aluminium oxide inserts. In addition, Caco-2 cells grown on these two inserts were not comparable with respect to cell morphology, cell numbers and transepithelial electrical resistance. The low adsorption potential of the aluminium oxide inserts, particularly for high molecular weight or lipophilic ligands, offers a distinct advantage over nitrocellulose inserts for drug transport studies. The carrier-mediated uptake and transport of the imino acid (L-proline) and the acidic amino acids (L-aspartate and L-glutamate) have been studied. At pH7.4, L-proline uptake is mediated via an A-system carrier. Elevated uptake and transport under acidic conditions occurs by activation of a distinct carrier population. Acidic amino acid transport is mediated via a X-AG system. The flux of baclofen, CGP40116 andCGP40117 across Caco-2 monolayers was described by passive transport. The transport of three peptides, thyrotrophin-releasing hormone, SQ29852 and cyclosporin were investigated. Thyrotrophin-releasing hormone transport acrossCaco-2 monolayers was characterised by a minor saturable (carrier-mediated,approximately 25%) pathway, superimposed onto a major non-saturable (diffusional)pathway. SQ29852 uptake into Caco-2 monolayers is described by a major saturable mechanism (Km = 0.91 mM) superimposed onto a minor passive component. However, the initial-rate of SQ29852 transport is consistent with a passive transepithelial transport mechanism. These data highlight the possibility that itsbasolateral efflux is severely retarded such that the passive paracellular transportdictates the overall transepithelial transport characteristics. In addition, modelsuitable for investigating the transepithelial transport of cyclosporin A has been developed. A modification of the conventional Caco-2 model has been developed which has a calcium-free Ap donor-solution and a Bl receiver-solution containing the minimumcalcium concentration required to maintain monolayer integrity (100 μM). The influence of calcium and magnesium on the absorption of [14C]pamidronate was evaluated by comparing its transport across the conventional and minimum calciumCaco-2 models. Ap calcium and magnesium ions retard the Ap-to-Bl flux of pamidronate across Caco-2 monolayers. The effect of self-emulsifying oleic acid-Tween 80 formulations on Caco-2monolayer integrity has been investigated. Oleic acid-Tween 80 (1 0:1) formulations produced a dose-dependent disruption of Caco-2 monolayer integrity. This disruption was related to the oleic acid content of the formulation.

No description available.

The objective of this project was to develop new controlled drug delivery systems using nanomeric particles and characterize the delivery of drugs into cells in real time by digital fluorescence imaging microscopy techniques. The project is based on the idea that it could be possible to improve efficacy of drug molecules when encapsulated in nanometer-sized particles. Due to their small dimensions the particles could permeate through cells and tissues and even through the blood brain barrier. The anti-cancer drug Doxorubicin was encapsulated into biodegradable Poly (DL-lactideco- glycolide) (PLGA) nanoparticles by simple nanoprecipitation method. The small size of these particles (<200nm) could be beneficial to realize passive tumor-targeted drug delivery through enhanced permeability and retention (EPR) effects. These drug-containing particles showed a sustained release profile. Fluorescence images indicated that these particles can be internalized by human breast cancer MCF-7 cells by non-specific endocytosis. The bioactivity of the drugs was also tested against cell culture. The results indicated that DXR-loaded PLGA nanoaprticles could be used to deliver Doxorubicin into breast cancer cells.

Patient compliance is a major factor in achieving optimal therapeutic outcomes. Pill burden, due to multiple drug therapies, has a great detrimental impact on compliance of the patient. Dose-dependent side-effects, associated with peak-trough plasma fluctuations of drugs, also have a negative impact on patient compliance with drug therapy. It is under these circumstances that zero-order drug release kinetics proves to be ideal. This is due to the lack of peak-trough fluctuations that occur with zero-order drug release, thereby minimizing the side-effects of drug therapy. Furthermore, a drug delivery system that may deliver more than one drug at a time may be beneficial to alleviate the pill burden associated with chronic diseases or specific health conditions. Novel drug delivery systems have been developed that offer zero-order or linear drug release. Amongst such systems are multilayered tablets. However these systems generally offer the delivery of just one drug. The development of a delivery system that is able to deliver up to three drugs in a zero-order manner may prove to be significantly beneficial to greatly increase patient compliance and in turn therapeutic efficacy. The purpose of this study was to design a novel triple-layered tablet (TLT) matrix targeted at achieving stratified zero-order drug release. The central factor for the establishment of the TLT was the selection of ideal and novel polymers that are capable of acting as superior drug release matrices. Modified polyamide 6,10 (PA6,10) and salted-out poly(lactic-co-glycolic acid) (PLGA) were employed as the outer drug-carrier matrices whereas poly(ethylene oxide) (PEO) was used as the middle layer drug matrix. Specialized granulation techniques and direct compression were employed to prepare the TLT matrices. Diphenhydramine HCl, ranitidine HCl and promethazine were chosen as model drugs for the study due to their similar high aqueous solubilities (100mg/mL). Matrix hardness, gel strength, swelling/erosion characteristics, Fourier Transform Infrared spectroscopy, Differential Scanning Calorimetry and in vitro drug release analysis employing High Performance Liquid Chromatography were performed on the TLT matrices in order to determine the physicomechanical and physicochemical nature of the TLT matrices. Computational molecular modeling (CMM) was employed to characterize the formation and dissolution of the TLT matrices. A box-Behnken experimental design was employed that resulted in the generation of 17 design formulations for ultimate optimization. In vivo animal studies were performed in the Large White Pig model to assess drug release behavior of the TLT. Ultra Performance Liquid Chromatography was employed for plasma sample analysis. The PA 6,10 layer provided relatively linear and controlled drug release patterns with an undesirable burst release greater than 15%, which upon addition of sodium sulphate was greatly reduced. The addition of PEO to the salted-out PLGA layer greatly reduced the initial burst release that occurred when salted-out PLGA matrix was used alone. Desirable results were obtained from FTIR, hydration and swelling/erosion analysis. CMM elucidated the possible mechanism of zero-order release from respective layers. Upon completion of the Box-Behnken design analysis, an optimized TLT formulation was established according to the formulation responses selected namely the rate constants and correlation coefficients. The TLT displayed desirable near linear release of all three drugs simultaneously over 24 hours, with approximately 10%, 50% and 90% of the drugs released in 1, 10 and 24 hours. An in vitro drug release comparison performed between the optimized TLT and the commercial tablets currently used, showed an unequivocal display of superiority of the TLT in terms of linear drug release over commercial tablets. A cardiovascular related drug regimen (Adco-simvastatin®, DISPRIN CV® and Tenormin 50®) was applied to the TLT to assess the flexibility of incorporating a range of drugs. The TLT furthermore provided near linear to linear release of the therapeutic regimen over 24 hours and maintained superiority over the commercial tablets. Benchtop Magnetic Resonance Imaging, porosity analysis and Scanning Electron Microscopy was utilized for further introspective characterization of the TLT. In vivo analysis demonstrated a definite control of drug release from the TLT as compared to commercial tablets which further confirmed the advantage of the TLT.

Effective treatment of ocular diseases presents a formidable task, dually attributed to their nature, and the presence of the ocular barriers. This was exemplified in the presented review of developments in ocular drug delivery systems. Conceptualization of novel polymeric systems with intelligent (e.g. stimulus-responsive) mechanisms and advances in nanotechnology are at the forefront of achieving directed and controlled delivery for treating vision-threatening diseases. It was thus the pertinent goal of this investigation to assimilate these observations in the design of an intelligent ocular drug delivery system. The design of an autofeedback polymeric platform, employing biodegradable polymers is exemplified through the implementation of two-way communication systems between our bodies and the delivery platform to create innovative drug delivery systems that recognize a biochemical process that is characteristic of a disease, and then responding via drug release. To achieve this intelligence in design, the delivery platform was based on novel stimulus-responsive polymeric materials. The concept of an autofeedback polymeric platform was intrinsically implemented in the design of an intelligent intraocular implant - called the I3 - employing inflammation-responsive polymers, having application as a smart release system capable of delivering controlled therapeutic levels of anti-inflammatory and/or antibiotic drug/s for posterior segment disorders of the eye in response to inflammation and infection. Inner and outer bioresponsive polymeric matrices (BPMs) were designed that released the incorporated anti-inflammatory and antibiotic in a fashion responsive to a stimulus, such as the highly reactive intermediates including hydroxyl radicals (OH.) that are released from activated leukocytes both in vitro and during acute and chronic intraocular inflammatory reactions in vivo (Hawkins and Davies, 1996). The first step in developing the intelligent device implicated design of an anti-inflammatory nanosystem (NS) with satisfactory size and surface properties, adequate permeation potential, uptake by inflamed cells, low cellular toxicity, and enhanced anti-inflammatory effect availed to the incorporated drug. A composite lipoidal-polymeric NS was developed (Lipo-Chit-PCL NS) and compared to a purely polymeric NS. The NS was ultimately enclatherated as a NS-polymer superlattice, forming the inner BPM of the I3. The designed composite lipoidal-polymeric NS attested its significant potential for selective drug delivery to inflamed tissues, demonstrating significantly enhanced tissue permeation, cell uptake, and anti-inflammatory activity compared to an indomethacin suspension. Subsequent molecular modeling revealed that the composite NS displayed an enhanced lipophilicity and superior cellular internalization efficiency. The preferred NS was subsequently selected for optimization via a Plackett-Burman Statistical Design Method. Design of the NS was proceeded by development and optimization of the inner and outer BPMs, being the stimulus-responsive component of the device, via implementation of a novel methodology for simultaneous design of the two intimately crosslinked matrices. Inflammation-responsive polymers such as hyaluronic acid, alginate, poly(acrylic) acid, and chitosan, were ultimately selected for design of the I3drug delivery system. Intensive device optimization was then undertaken, first employing a Response Surface Methodology, embodied by the Box-Behnken Design, ensued by Artificial Neural Networks. Characterization of the drug release kinetics from the optimized I3 is pivotally provided, as well as molecular modeling. The reagent (N-hydroxysuccimide, NHS) and catalyst employed (aluminium chloride, AlCl3) had a significant or notable effect on the mean dissolution time of indomethacin under normal and pathological conditions, respectively (p=0.048; p=0.058). The interaction between the inflammation-responsive hyaluronic acid and carbodiimide crosslinker emanated in a significant effect on the change in mean dissolution time of indomethacin from normal to inflammatory conditions (p=0.050). Subsequent execution of ANN with further training of the data confirmed the adequacy of the design. Analysis of the drug release kinetics from the optimum I3 under both normal and pathological conditions was in coherence with the anticipated behavior of an inherently bioresponsive device. Molecular simulations generated provided clear evidence for the catalytic effect of the hydroxyl radicals, specifically in hyaluronic acid hydrolysis. It was imperative to elucidate the intricate modus operandi of the optimized I3. The intricately crosslinked polymeric system comprising the I3 responds at an innate level predicted by its molecular make-up to inflammatory conditions as indicated by the results of the rheological analysis, MRI and SEM imaging. FTIR explicated the formation of pivotal intra- and intermolecular bonds within and between the inflammation-responsive polymers of the I3, while TMDSC confirmed the extent to which the composite polymeric system had altered from its native consituents to form a device of the desired functionality. Tensile analysis provided an indication of the overall mechanical performance of the implant. The porosity ascertained for both the inner and outer BPMs was a predictor of the overall internal architecture and potential drug release characteristics of the BPMs comprising the I3, as were critical morphological changes, visualized via SEM and interpreted via image analysis displayed during device erosion. Furthermore, molecular mechanics simulations were carried out to model the interaction between the polymeric components of the inner and outer BPM and confirmed the formation of a ‘secure-fit’ dual polymeric matrix system by highlighting the anticipated interconnectivity between the inner and outer BPM of the I3. The in vivo performance of the device was assessed to further provide a convincing argument as to the ocular suitability and overall contrasting performance under normal and inflammatory conditions. Histological assessment was key to predicting significant inflammatory changes, as well as reductions in inflammation initiated by the I3. Analysis of ocular drug levels under normal and inflammatory conditions was undertaken for correlation with in vitro results, for ultimate establishment of an in-vitro-in-vivo correlation (IVIVC). The device was well-tolerated following implantation in the rabbit eye. Investigations of drug concentrations attained and device erosion were a good indication that the I3 expresses bioresponsive capabilities in vivo. There was enhanced release of both drugs in the inflamed rabbit eye even after 7 days (the maximum period in which the induced inflammation was permitted to ensue), with indomethacin levels of 0.749±0.126μg/mL and 1.168±0.186μg/mL, and ciprofloxacin levels of 1.181±0.150μg/mL and 6.653±0.605μg/mL being attained in the normal and inflamed eye, respectively. At 28 days in the normal eye, concentrations of indomethacin detected were only 0.564±0.111μg/mL and those of ciprofloxacin were 1.226±0.209μg/mL. Furthermore, the enhanced erosion of the I3 in the inflamed eye is also exemplified, with the I3 eroding 1.504±0.505% in the normal eye and 22.609±2.421% in the inflamed eye after 7 days; and only reaching 13.830±1.010% erosion after 28 days in the normal rabbit eye. Elaboration of the IVIVC undertaken for both indomethacin and ciprofloxacin approached or attained a Level A correlation, respectively, and provided further evidence for the feasibility of the I3 and for advancement of this concept toward application in a clinical setting. Establishment of such a correlation for the inflamed rabbit eye would be the main consideration in prospective investigations.

M.Pharm., Faculty of Health Sciences, University of the Witwatersrand, 2011 / Periodontal disease describes a chronic bacterial infection affecting the gums and bone supporting the teeth. Bacteria present in plaque produce toxins, which lead to a cascade of inflammatory events that if left untreated may lead to permanent tooth loss. A periodontal pocket forms when the free gingiva moves away from the tooth surface. Periodontal disease is prevalent worldwide and has risk factors such as HIV and diabetes with possible links to socio-economic status. This places a large portion of the South African population at risk in an already burdened health care system. Scaling and root planning (SRP) forms the keystone of periodontal therapy, involving the removal of calculus and plaque. Multiple clinical trials have proved SRP leads to improved clinical outcomes. However, it often leaves behind microorganisms leading to recolonisation. Administration of pharmacological therapy is used in combination with SRP delivering one or more drugs. Subgingival treatment of periodontal disease involves the placement of a drug delivery device within the periodontal pocket releasing model drugs over a prolonged period of time. Targeted drug delivery devices have been the focus of periodontal research over the past two decades. To date there are no commercially available local drug delivery devices in South Africa for the treatment of periodontal disease. The aim of this study was to design, formulate and evaluate (in vitro) a novel polymeric fibre system to locally deliver an antimicrobial and an anti-inflammatory drug over 10 days to the periodontal pocket for the treatment of periodontal disease. The design of a flexible fibre would easily fit within the periodontal pocket evenly delivering the model drugs to the affected site. Alginate combined with glycerol was crosslinked with barium cations forming a monolithic fibre incorporating ciprofloxacin and diclofenac sodium, as the model antimicrobial and anti-inflammatory agents respectively. A 3-Factor Box-Behnken Design was employed to statistically optimise the fibres according to their tensile properties and drug release. The optimised formulation (3.14%w/v alginate, 22.54mL glycerol and 10.00w/v barium chloride) was evaluated for its drug release and hydration behaviour at pH 4 and 6.8, vibrational transitions and tensile properties as well as antimicrobial assays, characterising the in vitro behaviour of the device. The pH of the periodontal pocket varies from pH 2-9. Crosslinked alginate matrices demonstrate pH-responsive behaviour, therefore the polymeric fibre device was tested at pH 4 and 6.8. Drug release at pH 4 occurred as a result of drug diffusing through the polymeric fibres. However, at pH 6.8 the disruption of the fibre structure led to drug release as a consequence of the swelling and erosion of the matrix. Ciprofloxacin was sufficiently released from the drug-loaded fibres inhibiting growth of Escherichia coli, Enterococcus faecalis and Streptococcus mutans over 10 days. The physicomechanical and physicochemical properties were related to the degree of crosslinking, the effect of the plasticiser and the interaction of formulation components. The polymeric fibre device formed a strong yet flexible biodegradable matrix which simultaneously released an antimicrobial and anti-inflammatory agents in phosphate buffer solution pH 6.8 over 10 days. The promising in vitro results advocate for further analysis of the fibres.

The poor response of patients to high-dose chemotherapy commonly associated with the treatment of solid tumors has led to research efforts in the development of implants for the delivery of drug directly to solid tumors. In order to prevent surgical complications associated with the placement of an implant at the site of the tumor, efforts have been made to develop implants which form at the site of the tumor. This study aimed to develop an In Situ Forming Implant (ISFI) which was responsive to temperature and able to form an implant when injected into the body and to release drug over a period exceeding one month. To this end, a thermoresponsive polymer, poly(methyl vinyl ether) was selected and following preformulation studies to assess release and gelation temperature, a Design of Experiments approach was utilised to formulate an optimal formulation. Fourteen formulations were prepared according to a Face-Centred Central Composite Design selected and were assessed for gelation temperature, ease of injectability and Mean Dissolution Time. Utilising the experimental values obtained, regression models for each of the outcomes were generated. The optimal formulation was then determined by selecting the appropriate targets for each of the responses in the design. The optimal formulation was able to gel at body temperature, could be injected into the body and showed release of entrapped chemotherapeutic, methotrexate for a period exceeding one month. pH-responsive microparticles were also formulated and optimized using a Face-Centred Central Composite Design. Optimized particles were then loaded into the optimized ISFI and displayed faster release of the entrapped drug than with the dispersed drug. In vitro testing of the ISFI was conducted against solid tumor forming cells and in vivo testing was conducted in healthy Sprague-Dawley rats. A few rats developed toxicity to methotrexate after 6 days, however, low quantities of drug were found in the plasma. In addition, drug was present in the surrounding tissue in a high concentration even after 10 days.

Thesis (M.Pharm.)--University of the Witwatersrand, Faculty of the Health Sciences, 2013. / The oral route presents the most convenient, least invasive and thus the most widely used route for the administration of drugs but displays inherent impediments, related to both the drugs used and the gastrointestinal tract itself, resulting in diminished bioavailability of drugs. Additionally, development of new drug molecules is difficult, expensive, time-consuming and their approval and success is not guaranteed. Development of novel controlled Multiparticulate Oral Drug Delivery Systems (MODDS) aims to address these issues by employing existing drugs and enhancing their oral bioavailibility and safety, thus improving clinical efficacy in many disease states. Multiparticulate drug delivery systems are specialized controlled drug delivery systems that comprise of many discrete units, each loaded with a fraction of the total dose and each possessing the ability to release entrapped drug independently, thus preventing dose dumping and allowing diverse applications within a single dosage form. However, novel drug delivery systems possess disadvantages in that they may be expensive, difficult to reproduce on a large-scale and frequently use synthetic polymers that may not be disintegrated nor excreted to a sufficient extent in vivo. Starch, a natural polymer, is widely available, inexpensive, and biocompatible and can be modified in various ways. Starch is thus available in several forms and compositions, including commercial multiparticulates, allowing it to be used for the development of an effective controlled MODDS. The essential aim of the study was to functionalize the inert, inexpensive, commercially available, food-grade multiparticulates derived from sago or tapioca starch and employ the multiparticulates as a Starch-Based Platform (SBP) in a MODDS. Following characterization of both starch-based multiparticulates, the sago multiparticulates were selected as the SBP and preliminary optimization of drug entrapment employing diphenhydramine (DPH) as the model drug was conducted using a Box-Behnken experimental design. The pre-optimized formulation displayed superior Drug Entrapment Efficiency (DEE= 59.354%, R2=0.9257 when compared to the predicted DEE), but demonstrated poor control of drug release. Thus, alternate drugs displaying varying physicochemical characteristics were evaluated and sulfasalazine (SSZ) was ultimately selected as the model drug for the study. Various modifications of the SBP were attempted with epichlorohydrin-facilitated crosslinking followed by SSZ loading and finally secondary epichlorohydrin crosslinking conferring the best control of drug release coupled with satisfactory drug entrapment and excellent SBP structural stability. The formulation procedure was optimized using a Face Centered Central Composite Design by evaluating the effects of varying the drug loading time (DLT) and secondary crosslinking time (CLT) on the responses of DEE and Mean Dissolution Time (MDT). The optimum formulation conditions was established as DLT=8 hours and CLT=8 hours with predicted DEE and MDT of 40.78% and 171.696 minutes, respectively. Formulation, scaling up and analysis of the optimized SBP revealed that gelatinization and crosslinking had occurred throughout the SBP resulting in incorporation of SSZ into the structure of the SBP, both at the surface and at the core of the SBP. Experimental DEE values for the optimized and scaled-up formulations demonstrated close correlation to the predicted DEE with R2 values of 0.9813 and 0.9893, respectively. The modifications imparted during optimization caused coalescence of the surface starch granules and resulted in a decrease in surface area and porosity of the SBP. This in turn affected the drug release resulting in MDT values of 163.972 and 166.011 minutes, which translated into R2 values of 0.9550 and 0.9669 for the optimized and scaled-up formulations, respectively. Drug release from the optimized SBP formulation was found to fit the Higuchi model best with Quasi-fickian diffusion occurring in simulated gastric fluid and anomalous drug transport in simulated intestinal fluid resulting in an overall anomalous drug transport mechanism of drug release. In vivo SSZ release throughout the gastrointestinal tract was determined directly by measuring plasma SSZ concentrations and indirectly by measuring the plasma concentrations of 5-Acetyl Salicylic Acid (5-ASA) and N-Acetyl-5-ASA and displayed general correlation to the in vitro SSZ behavior determined previously. Furthermore, the in vivo SSZ release of the optimized SBP formulation was compared to a conventional commercially available SSZ formulation, Salazopyrin® with the optimized SBP formulation displaying superior SSZ release characteristics and a vast improvement in the bioavailability of SSZ compared to Salazopyrin®.