ResearchSpace :: Browsing by Author "Labuschagne, Philip W"

Browsing by Author "Labuschagne, Philip W"

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CO2-assisted production of polyethylene glycol / lauric acid microparticles for extended release of Citrus aurantifolia essential oil
(Elsevier, 2020-05) Akolade, Jubril O; Olubukola Nasir-Naeem, K; Swanepoel, Andri; Yusuf, AA; Balogun, Mohammed O; Labuschagne, Philip W
Applications of essential oils as chemotherapeutics are limited because these aromatic oils are generally volatile, insoluble in aqueous media and easily degraded to non-active constituents when subjected to thermal-oxidative processes. The particles from gas-saturated solution (PGSS) technology allows for non-destructive processing of volatile oils into micronized formulations under high pressure and moderate temperature using supercritical carbon dioxide (scCO2). In this study, essential oil from lime (Citrus aurantifolia) with proven antidiabetic activity was processed with polyethylene glycol (PEG) and lauric acid (LA) using scCO2 in a high pressure reactor for 2 h at 120 bar and 45 °C. The polymer-oil mixtures were co-precipitated and micronized through a 500 µm nozzle. PGSS processing of C. aurantifolia oil with PEG and LA yielded roughly spherical microparticles with sizes ~ 2 µm. Inclusion of the LA and encapsulation of the limonene-rich oil into the PEG particles were confirmed using FTIR and GC/MS respectively. Melting point and heat of fusion of the PEG/LA microparticles were lower when compared with particles produced with PEG only, resulting in higher oil loading capacity and yield. The scCO2-assisted polymeric encapsulation of the volatile oil reduced rapid vaporization and incorporation of LA with the PEG-oil formulation extended the mean release time in simulated physiological solutions. Free radical scavenging and alpha-amylase inhibitory activities of the lime oil were also preserved following encapsulation in the PEG/LA microparticles. In summary, production of PEG/LA microparticles with high yield and loading capacity of bioactive lime essential oil was achieved using the scCO2 encapsulation technology.
Compatibility of polyvinyl alcohol and poly(methyl vinyl ether-co-maleic acid) blends estimated by molecular dynamics
(Elsevier Science Ltd, 2005-07-25) Moolman, FS; Meunier, M; Labuschagne, Philip W; Truter, PA
The CSIR has developed a novel oxygen barrier technology for plastics packaging based on interpolymer complex formation between PVOH (polyvinyl alcohol) and PMVE-MA (poly(methyl vinyl ether-co-maleic acid)). As interpolymer complexation interactions are strongly dependent on stoichiometric ratios, the estimation of the optimum blend ratio is an important component of blend design. This study used molecular dynamics modelling to predict the ratio of optimum interaction for PVOH: PMVE-MA blends. Amorphous cells were constructed containing blends of short-chain repeat units of PVOH and PMVE-MA. The oligomers were equilibrated using both NVT and NPT dynamics and the cohesive energy densities (CED's) of the models were computed. From the CED's, energies of mixing and Flory-Huggins Chi Parameter (chi) values were estimated. The chi-values were negative for all blends, indicating favourable interaction between the two polymers. The minimum chi-values were found around 0.6-0.7 mass fraction of PMVE-MA, which agrees well with experimental viscosity results (this work), which indicated optimum interaction around 0.7 mass fraction PMVE-MA. These results confirm that molecular dynamics can be used as a tool for investigating interpolymer complexation phenomena.
Dammarane-type triterpenoids with anti-cancer activity from the leaves of Cleome gynandra
(2021-06) Mzondo, Buntubonke; Dlamini, Nomusa; Malan, FP; Labuschagne, Philip W; Bovilla, VR; Madhunapantula, SV; Maharaj, V
Three dammarane-type triterpernoids including two new ones, cleogynones A and B (1 and 2), were isolated from the leaves of Cleome gynandra. The structures of the new triterpenoids were elucidated by spectroscopic data analysis and confirmed by single crystal X-ray crystallography. All three compounds showed moderate cytotoxicity against breast cancer (MDA-MB-468), cleogynone B (2) and compound (3) further showed cytotoxicity against colorectal cancer (HCT-116 & HCT-15). Cleogynone B was also moderately active against lung cancer (A549).
Encapsulating probiotics with an interpolymer complex in supercritical carbon dioxide
(Acad Science South Africa A S S AF, 2006) Moolman, FS; Labuschagne, Philip W; Thantsa, MS; Van der Merwe, TL; Rolfes, H; Cloete, TE
Traditional encapsulation methods in fortified foods and drug delivery applications present difficulties for ‘actives’, such as probiotics, sensitive to exposure to water, solvents, heat or oxygen, where ‘active’ refers to a material, chemical or organism that has some potential benefit when consumed. In this paper authors present a novel encapsulation technology, based on interpolymer complex formation in supercritical carbon dioxide, which avoids such exposure during the encapsulation process. The method was used to encapsulate indomethacin and Bifidobacterium longum in a poly(vinyl pyrrolidone)–poly(vinyl acetate–co-crotonic acid) interpolymer complex. Polymer complexation was confirmed by Fourier Transform infrared and moisture absorption studies. Polymer plasticization and release of encapsulated probiotics were studied with scanning electron microscopy. It was shown that the encapsulation matrix is stable at low pH, but disintegrates at higher pH, triggering release of the encapsulated material. The technology could find application in encapsulation of sensitive actives in the food and pharmaceutical industry
Formation of an interpolymer complex in supercritical carbon dioxide and its application in the encapsulation of probiotics
(2006-02-27) Moolman, S; Labuschagne, Philip W; Thantsha, MS; Van der Merwe, TL; Cloete, TE
Traditional encapsulation methods present difficulties for sensitive actives such as probiotics, due to exposure to water/solvents, heat, oxygen, etc. The authors present a novel encapsulation technology utilising the formation of an interpolymer complex in a supercritical carbon dioxide environment. Interpolymer complex formation was confirmed through FTIR and moisture absorption studies. Polymer liquefaction and release of encapsulated probiotics were studied with SEM. Indomethacin and B. longum were encapsulated using the method, with poly(vinyl pyrrolidone) and poly(vinyl acetate-co-crotonic acid) as interpolymer complex. The polymer system provides protection at low pH, while releasing at higher pH. Potential applications include encapsulation of sensitive actives in the food and pharmaceutical industry
Impact of wall material physicochemical characteristics on the stability of encapsulated phytochemicals: A review
(Elsevier, 2018-05) Labuschagne, Philip W
Phytochemicals are plant-derived chemicals that have a number of protective or health-promoting properties. However, their health benefits and thus commercial potential can be restricted due to their instability to environmental factors such as moisture, heat, light, oxygen etc. A common approach to improve stability is via encapsulation whereby the phytochemical is encased inside a wall material, thereby forming a protective barrier between the phytochemical and the external environment. The impact of a wide range of wall materials and their combinations on the stability of various phytochemicals has been studied in the last twenty years. This review focuses on the specific inherent physicochemical characteristics of the wall material as well as the encapsulation process dependant physical characteristics that has shown to have the greatest impact on the stability of encapsulated phytochemicals. The information contained in this review could assist researchers in addressing some of the most important considerations when designing a wall material for increased phytochemical stability.
In situ FTIR spectroscopic study of the effect of CO2 sorption on H-bonding in PEG–PVP mixtures
(Elsevier Publishers, 2011-05) Labuschagne, Philip W; Kazarian, SG; Sadiku, RE
A study of the H-bonding between poly(ethylene glycol) (PEG) and polyvinylpyrrolidone (PVP) in the presence of supercritical carbon dioxide at various temperatures, pressures, different M(w) of PEG and PVP and different PEG/PVP ratios is presented. In situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was used to investigate H-bonding by examining changes in the relative intensities and positions of peak maxima of the 2nd derivative (CO) bands associated with 'free' and H-bonded CO groups. In general, relative intensities of bands associated with H-bonded CO groups decreased upon CO(2) sorption and was accompanied by an increase in intensity of bands associated with 'free' CO groups. At the same time, these bands were shifted to higher wavenumbers. These shifts were attributed to the shielding effect of CO(2) molecules on H-bonding interactions between PEG and PVP. The magnitude of the effects of CO(2) shielding generally increased with decreasing polymer M(w) and increasing CO(2) content. However, upon CO(2) venting the extent of the H-bonding between PEG and PVP reappeared. The extent of H-bonding recovery was greatest for blends with low M(w) PEG (M(w): 4×10(2)) and PVP (M(w): 9×10(3)) and PEG content =0.54wt% under mild conditions of pressure (80bar) and temperature (35°C). For the same low M(w) blends, increasing pressure to 150bar, or temperature to 50°C, showed poor H-bond recovery upon CO(2) venting. Overall, it was shown that supercritical CO(2)-induced shielding of H-bonding interactions in polymer blends is reversible upon CO(2) venting, and the magnitude of both was influenced by processing conditions and blend composition.
Investigation of the degree of homogeneity and hydrogen bonding in PEG/PVP blends prepared in supercritical CO2: comparison with ethanol-cast blends and physical mixtures
(Elsevier, 2010-07) Labuschagne, Philip W; John, Maya J; Sadiku, RE
The degree of homogeneity and H-bond interaction in blends of low-molecular-mass poly(ethylene glycols) (PEG, Mw = 400, 600, 1000) and poly(vinylpyrrolidone) (PVP, Mw =9×103) prepared in supercritical CO2, ethanol and as physical mixtures were studied by differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy and dynamic mechanical analysis (DMA) techniques. Homogeneity of samples prepared in supercritical CO2 were greater than physically mixed samples, but slightly less than ethanol-cast samples. PEG–PVP H-bond interaction was higher for ethanol-cast blends when compared to blends prepared in supercritical CO2. This reduced interaction was attributed to a combination of: (1) shielding of PEG–PVP H-bond interactions when CO2 is dissolved in the blend; (2) rapidly reduced PEG and PVP chain mobility upon CO2 venting, delaying rearrangement for optimum PEG–PVP H-bond interaction.
Measurement of phase transition, density and viscosity of supercritical carbon dioxide-Fischer-Tropsch wax mixtures2025
(2025-06) Swanepoel, Andri; Labuschagne, Philip W; Schwarz, CE
Melting temperature, phase behaviour and densities of binary mixtures of CO 2 and three Fischer-Tropsch waxes with varying molecular weights were experimentally determined. The melting temperatures of the lower molecular weight waxes increased with CO 2 pressure, and pressure induced crystallisation of the lowest molecular weight wax occurred above 20 MPa. CO 2 solubility in the waxes decreased with increasing wax molecular weight. Trends in mixture densities with changes in temperature and pressure mimicked that of pure CO viscosity of the lowest molecular weight wax decreased with increased CO 2 2 . The concentration, and decreased with increases in temperature and pressure, with the impact of pressure minimised above the temperature inversion point. Solubility data were correlated with a modified Chrastil and the Mendez-Santiago & Teja models. The Chrastil model accurately predicted solubility of CO 2 in all three waxes to within 1 % of the measured values.
Microencapsulation of eucalyptol in polyethylene glycol and polycaprolactone using particles from gas-saturated solutions
(2019-10) Akolade, Jubril O; Balogun, Mohammed O; Swanepoel, Andri; Ibrahim, RB; Yusuf, AA; Labuschagne, Philip W
Eucalyptol is the natural cyclic ether which constitutes the bulk of terpenoids found in essential oils of Eucalyptus spp. and is used in aromatherapy for treatment of migraine, sinusitis, asthma and stress. It acts by inhibiting arachidonic acid metabolism and cytokine production. Chemical instability and volatility of eucalyptol restrict its therapeutic application and necessitate the need to develop an appropriate delivery system to achieve extended release and enhance its bioactivity. However, the synthesis method of the delivery system must be suitable to prevent loss or inactivation of the drug during processing. In this study, supercritical carbon dioxide (scCO2) was explored as an alternative solvent for encapsulation and co-precipitation of eucalyptol with polyethylene glycol (PEG) and/or polycaprolactone (PCL) using the particles from gas-saturated solution (PGSS) process. Polymers and eucalyptol were pre-mixed and then processed in a PGSS autoclave at 45 °C and 80 bar for 1 h. The mixture in scCO2 was micronized and characterized. The presence of eucalyptol in the precipitated particles was confirmed by infrared spectroscopy, gas chromatography and mass spectrometry. The weight ratios of PEG–PCL blends significantly influenced loading capacity and encapsulation efficiency with 77% of eucalyptol encapsulated in a 4 : 1 composite blend of PEG–PCL. The particle size distribution of the PGSS-micronized particles ranged from 30 to 260 μm. ScCO2 assisted microencapsulation in PEG and PCL reduced loss of the volatile drug during a two-hour vaporization study and addition of PCL extended the mean release time in simulated physiological fluids. Free radical scavenging and lipoxygenase inhibitory activities of eucalyptol formulated in the PGSS-micronized particles was sustained. Findings from this study showed that the scCO2-assisted micronization can be used for encapsulation of volatile drugs in polymeric microparticles without affecting bioactivity of the drug.
Micronization, characterization and in-vitro dissolution of shellac from PGSS supercritical CO2 technique
(Elsevier, 2016-02) Labuschagne, Philip W; Naicker, B; Kalombo, Lonji
The purpose of this investigation was to determine whether shellac, a naturally occurring material with enteric properties, could be processed in supercritical CO2 (sc-CO2) using the particles from gas saturated solution (PGSS) process and how process parameters affect the physico-chemical properties of shellac. In-situ attenuated total reflection fourier transform infra-red (ATR-FTIR) spectroscopy showed that CO2 dissolves in shellac with solubility reaching a maximum of 13% (w/w) at 300bar pressure and 40°C and maximum swelling of 28%. The solubility of sc-CO2 in shellac allowed for the formation of porous shellac structures of which the average pore diameter and pore density could be controlled by adjustment of operating pressure and temperature. In addition, it was possible to produce shellac microparticles ranging in average diameter from 180 to 300µm. It was also shown that processing shellac in sc-CO2 resulted in accelerated esterification reactions, potentially limiting the extent of post-processing "ageing" and thus greater stability. Due to additional hydrolysis reactions enhanced by the presence of sc-CO2, the solubility of shellac at pH 7.5 was increased by between 4 and 7 times, while dissolution rates were also increased. It was also shown that the in-vitro dissolution profiles of shellac could be modified by slight adjustment in operating temperatures.
Novel encapsulation method for probiotics using an interpolymer complex in supercriticial carbon dioxide
(2006-10) Moolman, FS; Labuschagne, Philip W; Thantsha, MS; Van Der Merwe, TL; Rolfes, H; Cloete, TE
The CSIR has developed a novel scCO2-based encapsulation technology utilizing interpolymer complex formation to improve the barrier properties of the polymer system. In this paper the auhtors report some results obtained in the application of the technology in encapsulation of indomethacin and Bifidobacterium longum Bb-46
Plasticisation and complexation of certain polymers in supercritical CO2
(Research Gate, 2004-09) Labuschagne, Philip W
A polymer system (polyvinylpyrrolidone + polyvinyl acetate-co-crotonic acid) was successfully identified for use as encapsulation material for sensitive actives using supercritical CO2 as plasticisation medium, having the following properties: 1. Ability to plasticise sufficiently in supercritical CO2, 2. Ability to form an inter-polymer complex in supercritical CO2, 3. Ability to swell in aqueous medium in order to release actives, and 4. FDA-approved.
Polymer/layered silicates nanocomposites for barrier technology
(Wiley-Scrivener, 2012-02) Labuschagne, Philip W; Moolman, S; Maity, Arjun
Plastics are used increasingly in packaging applications due to a number of favorable properties, such as versatility, low weight, and low cost. However, their biggest drawback when compared to traditional packaging materials, such as glass and metals, is their relatively high permeability to gases and vapors. Specifically in food and beverage packaging, low permeability to oxygen is critical. This area of research has challenged polymer scientists, material scientists, physicists, and chemists all over the world to fabricate new nanocomposite materials for specialized applications. They have shown that the incorporation of layered silicates can significantly reduce the permeability of gases through plastics. This chapter is aimed at highlighting the interesting potential aspects of research on selective hybrid nanocomposite materials. The effect of aspect ratio and the degree of clay exfoliation and polymer-clay interaction on the gas permeability will be discussed along with the effect of the types of organic modifier, polymer chemical structure, nature of compatibilizer, blending sequence, processing conditions as well as clay loading on these properties.
Preclinical assessment of 68Ga-PSMA-617 entrapped in a microemulsion delivery system for applications in prostate cancer PET/CT imaging
(Wiley, 2019-06) Mandiwana, Vusani; Kalombo, Lonji; Lemmer, Yolandy; Labuschagne, Philip W; Semete-Makokotlela, Boitumelo; Sathekge, M; Ebenhan, T; Rijn Zeevaart, J
It has in recent years been reported that microemulsion (ME) delivery systems provide an opportunity to improve the efficacy of a therapeutic agent whilst minimising side effects and also offer the advantage of favourable treatment regimens. The prostate-specific membrane antigen (PSMA) targeting agents PSMA-11 and PSMA-617, which accumulate in prostate tumours, allow for [68 Ga]Ga3+ -radiolabelling and positron emission tomography/computed tomography (PET) imaging of PSMA expression in vivo. We herein report the formulation of [68 Ga]Ga-PSMA-617 into a ME ≤40 nm including its evaluation for improved cellular toxicity and in vivo biodistribution. The [68 Ga]Ga-PSMA-617-ME was tested in vitro for its cytotoxicity to HEK293 and PC3 cells. [68 Ga]Ga-PSMA-617-ME was administered intravenously in BALB/c mice followed by microPET/computed tomography (CT) imaging and ex vivo biodistribution determination. [68 Ga]Ga-PSMA-617-ME indicated negligible cellular toxicity at different concentrations. A statistically higher tolerance towards the [68 Ga]Ga-PSMA-617-ME occurred at 0.125 mg/mL by HEK293 cells compared with PC3 cells. The biodistribution in wild-type BALB/C mice showed the highest amounts of radioactivity (%ID/g) presented in the kidneys (31%) followed by the small intestine (10%) and stomach (9%); the lowest uptake was seen in the brain (0.5%). The incorporation of [68 Ga]Ga-PSMA-617 into ME was successfully demonstrated and resulted in a stable nontoxic formulation as evaluated by in vitro and in vivo means.
Preparation of rifampicin/poly(d,l-lactice) nanoparticles for sustained release by supercritical assisted atomization technique
(Elsevier, 2014-11) Labuschagne, Philip W; Adami, R; Liparoti, S; Naidoo, Saloshnee; Swai, H; Reverchon, E
In this work supercritical assisted atomization (SAA) process was used for the co-precipitation of poly(d,l-lactide) (PDLLA) and rifampicin (RIF) as nanoparticles for sustained release applications. The effect of the variation of PDLLA/RIF ratio on co-precipitate characteristics was mainly investigated. The precipitated particles were analyzed in terms of their morphological, thermodynamic and crystallographic properties. In addition, loading efficiency and in-vitro release studies were conducted. Spherical PDLLA/RIF nanoparticles with mean diameter ranging from 123 to 148 nm were prepared. Loading efficiency was greater than 100% resulting in RIF loadings of 28.8 to 50.5%. X-ray diffraction revealed that the encapsulated RIFis in an amorphous state, while NMR spectra indicated no structural modifications after the SAA pro-cess. In-vitro release studies showed an initial burst release of 80–87% of total RIF loaded, necessary to suppress the generation of resistance by the microorganism, followed by first-order sustained release between 0.4 and 0.8 mg/L RIF per day over a period of 17 days.
Supercritical antisolvent co-precipitation of rifampicin and ethyl cellulose
(Elsevier, 2017-05) Djerafi, R; Swanepoel, Andri; Crampon, C; Kalombo, Lonji; Labuschagne, Philip W; Badens, E; Masmoudi, Y
Rifampicin-loaded submicron-sized particles were prepared through supercritical anti-solvent process using ethyl cellulose as polymeric encapsulating excipient. Ethyl acetate and a mixture of ethyl acetate/dimethyl sulfoxide (70/30 and 85/15) were used as solvents for both drug and polymeric excipient. When ethyl acetate was used, rifampicin was crystallized separately without being embedded within the ethyl cellulose matrix while by using the ethyl acetate/dimethyl sulfoxide mixture, reduced crystallinity of the active ingredient was observed and a simultaneous precipitation of ethyl cellulose and drug was achieved. The effect of solvent/CO2 molar ratio and polymer/drug mass ratio on the co-precipitates morphology and drug loading was investigated. Using the solvent mixture, co-precipitates with particle sizes ranging between 190 and 230 nm were obtained with drug loading and drug precipitation yield from respectively 8.5 to 38.5 and 42.4 to 77.2% when decreasing the ethyl cellulose/rifampicin ratio. Results show that the solvent nature and the initial drug concentrations affect morphology and drug precipitation yield of the formulations. In vitro dissolution studies revealed that the release profile of rifampicin was sustained when co-precipitation was carried out with the solvent mixture. It was demonstrated that the drug to polymer ratio influenced amorphous content of the SAS co-precipitates. Differential scanning calorimetry thermograms and infrared spectra revealed that there is neither interaction between rifampicin and the polymer nor degradation of rifampicin during co-precipitation. In addition, stability stress tests on SAS co-precipitates were carried out at 75% relative humidity and room temperature in order to evaluate their physical stability. SAS co-precipitates were X-ray amorphous and remained stable after 6 months of storage. The SAS co-precipitation process using a mixture of ethyl acetate/dimethyl sulfoxide demonstrates that this strategy can be successful for controlling rifampicin delivery.
Supercritical carbon dioxide (CO2) assisted preparation of hydrogen-bonded interpolymer complexes
(2010-10) Labuschagne, Philip W
The use of supercritical CO2 as medium in polymer processing eliminates many of disadvantages associated with other means of processing, i.e. high temperatures or toxic solvents. The “soft” processing conditions make CO2 specifically suitable as medium in the preparation of polymeric drug delivery systems. A unique drug delivery system is based on interpolymer complexation, formed by the association of two polymers via, for instance, hydrogen bonding. Very limited information is available on hydrogen bonding behaviour between polymers in CO2, or how operating conditions and polymer properties affect such interactions. Drug-loaded polymer complexes prepared in CO2 have also not yet been investigated. First, the degree of homogeneity and H-bond interaction in blends of poly(ethylene glycol) (PEG) and poly(vinylpyrrolidone) (PVP) prepared in CO2, ethanol and as physical mixtures were studied. Homogeneity of samples prepared in CO2 were greater than physically mixed samples, but less than ethanol cast samples. This was attributed to differences in mass-transport properties under the various preparation conditions. The level of PEG-PVP H- bond interaction was higher for ethanol cast blends compared to blends prepared in CO2. This was attributed to: reduced PEG-PVP H-bond interaction in CO2 medium and rapidly reduced PEG and PVP chain mobility upon CO2 venting, delaying rearrangement for optimum interaction.
Supercritical CO2 interpolymer complex encapsulation improves heat stability of probiotic bifidobacteria
(Springer Verlag, 2014-02) Thantsha, MS; Labuschagne, Philip W; Mamvura, CI
The probiotic industry faces the challenge of retention of probiotic culture viability as numbers of these cells within their products inevitably decrease over time. In order to retain probiotic viability levels above the therapeutic minimum over the duration of the product's shelf life, various methods have been employed, among which encapsulation has received much interest. In line with exploitation of encapsulation for protection of probiotics against adverse conditions, we have previously encapsulated bifidobacteria in poly-(vinylpyrrolidone)-poly-(vinylacetate-co-crotonic acid) (PVP:PVAc-CA) interpolymer complex microparticles under supercritical conditions. The microparticles produced had suitable characteristics for food applications and also protected the bacteria in simulated gastrointestinal fluids. The current study reports on accelerated shelf life studies of PVP:PVAc-CA encapsulated Bifidobacterium lactis Bb12 and Bifidobacterium longum Bb46. Samples were stored as free powders in glass vials at 30 °C for 12 weeks and then analysed for viable counts and water activity levels weekly or fortnightly. Water activities of the samples were within the range of 0.25-0.43, with an average a(sub)w = 0.34, throughout the storage period. PVP:PVAc-CA interpolymer complex encapsulation retained viable levels above the recommended minimum for 10 and 12 weeks, for B. longum Bb46 and B. lactis Bb12, respectively, thereby extending their shelf lives under high storage temperature by between 4 and 7 weeks. These results reveal the possibility for manufacture of encapsulated probiotic powders with increased stability at ambient temperatures. This would potentially allow the supply of a stable probiotic formulation to impoverished communities without proper storage facilities recommended for most of the currently available commercial probiotic products.
Supercritical CO2-assisted preparation of ibuprofen loaded PEG-PVP complexes
(Elsevier Publishers, 2010-06) Labuschagne, Philip W; Kazarian, SG; Sadiku, RE
Stoichiometric ratios of poly (ethylene glycol) (PEG, Mw = 400) with poly(vinylpyrrolidone) (PVP, Mw = ±3.1 x 104 & Mw = 1.25 x 106 Mw) were prepared from ethanol cast solutions and in supercritical CO2. The complex formation was studied via glass transition (Tg) analysis obtained from differential scanning calorimetry (DSC) thermograms. PEG-PVP blends were also loaded with ibuprofen. The molecular dispersion of ibuprofen, mechanism of interaction, the effect of CO2 pressure and temperature and ageing of blends were also analysed with DSC, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and Xray diffraction. Tg analysis indicated that supercritical CO2 can facilitate the formation of stoichiometric PEG-PVP complexes. Processing of PEG-PVP blends with ibuprofen results in the molecular dispersion of ibuprofen mainly bonded to PVP carbonyl groups, without significant disruption of the PEG-PVP complex. Increasing ibuprofen content leads to the disruption of PEG-PVP H-bond interactions and subsequently a breakdown of the PEG-PVP complex. Increasing process pressure results in extraction of some PEG fractions, while temperature increase only leads to increased foaming. Post-processing ATR-FTIR shifts in ibuprofen-PEG-PVP complexes is greater with supercritical CO2 processing. These shifts are mainly attributed to atmospheric moisture absorption, however some evidence of molecular rearrangement is also observed. Altogether, ibuprofen-loaded PEG-PVP complexes can be prepared from supercritical CO2 processing showing similar characteristics to such complexes prepared from solution casting.

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