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  • SAGE Publications  (5)
  • 1
    Online Resource
    Online Resource
    Kinetic and Structural Modeling Mechanisms of Melatonin Transport from an Electrolytically Regulated Salted-out PLGA Scaffold
    SAGE Publications ; 2009
    In:  Journal of Bioactive and Compatible Polymers Vol. 24, No. 3 ( 2009-05), p. 266-296
    Details
    In: Journal of Bioactive and Compatible Polymers, SAGE Publications, Vol. 24, No. 3 ( 2009-05), p. 266-296
    Abstract: This study focused on optimizing the mechanism of zero-order active pre-programmed release of melatonin from a salted-out PLGA scaffold. A Box—Behnken design, modeled the formulations, required for optimizing the melatonin entrapment efficiency (EE), mean dissolution time at 30 days (MDT 30 ) and the release rate constant ( k). Response Surface Methodology depicted the influence of NaCl, CaCl 2 , and AlCl 3 on the release kinetics. Qualitative structural kinetic modeling and quantitative mathematical modeling of release data supported the kinetic events, interaction parameters, and melatonin transport phenomena that resolved the constraints governing the rate and extent of melatonin release. A salted-out PLGA chain was evaluated by rheological studies and braided rope-coiling and nonbraided nonrope coiling with dynamic simulations capturing the coherent structural transitions in the turbulent release medium with the influence of salts on the swelling or erosion, energy dissipation, and subsequent melatonin release. The release was mainly governed by erosion and not affected by time-dependent diffusion resistance (Hopfenberg model; n = 0.95; R 2 = 0.96; k e = 0.11—4.69×10 -3 mm/min; D = 0.110—0.893 × 10 -8 cm 2 /s; Deb release = 0.016—1.312). Swelling parameters confirmed that polymer swelling did not significantly influence melatonin release (δ = 0.232.00 mm, v = 0.027—0.181 cm/s, S w = 0.010—0.542). EE values ranged between 46% and 90% and were dependant on the salt type and concentration. AlCl 3 and NaCl blends increased the k values (0.0050) indicating their significance in melatonin release. The optimal scaffold (EE = 95%; MDT 30 = 1; k = 0.0050) was predicted to comprise 1.1451 and 0.8264 w/v of NaCl and AlCl 3 , respectively, with the exclusion of CaCl 2 in order to achieve zero-order kinetics over 30 days. The kinetic modeling approach enabled a qualitative and quantitative description of melatonin release patterns from the salted-out PLGA scaffolds thus facilitating the manipulation and prediction of drug release from PLGA modification by salting-out.
    Type of Medium: Online Resource
    ISSN: 0883-9115 , 1530-8030
    URL: Article
    DOI: 10.1177/0883911508099404
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2009
    detail.hit.zdb_id: 2073790-7
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  • 2
    Online Resource
    Online Resource
    A Novel Cellulose-Based Hydrophilic Wafer Matrix for Rapid Bioactive Delivery
    SAGE Publications ; 2007
    In:  Journal of Bioactive and Compatible Polymers Vol. 22, No. 2 ( 2007-03), p. 119-142
    Details
    In: Journal of Bioactive and Compatible Polymers, SAGE Publications, Vol. 22, No. 2 ( 2007-03), p. 119-142
    Abstract: A lyophilized polymeric wafer matrix was developed for rapid drug delivery via the oramucosal route. Lyophilization produced a porous wafer matrix that allowed simulated saliva (SS) to be rapidly absorbed into the hydrophilic structure. This surge of SS led to rapid disintegration of the wafer matrix. Hydroxypropylcellulose (HPC) was selected as the polymeric material based on its low gelatin potential. Other excipients incorporated into the system were lactose and mannitol as diluents, and glycine was utilized as a collapse inhibitor. A face-centered central composite design was employed to establish the significant effects of the independent formulation variables on the physico-chemical and physico-mechanical properties of the wafer matrix. The formulation variables investigated were, HPC concentration, diluent type and concentration, glycine concentration and fill volume. An analysis of these variables elucidated the influential factors that may be used to form an effective wafer matrix. HPC concentration significantly affected the wafer matrix disintegration rate ( P = 0.003), influx rate of SS ( P = 0.011) and wafer matrix friability ( P = 0.023). Diluent concentration had a significant effect on the wafer matrix tolerance ( P = 0.029) and wafer matrix friability ( P = 0.032). Statistical optimization was performed using constrained and artificial neural network techniques to predict ideal wafer formulation. Karl Fischer titrations revealed the reliability of the wafer matrices when small quantities of moisture were absorbed while being stored under ambient conditions.
    Type of Medium: Online Resource
    ISSN: 0883-9115 , 1530-8030
    URL: Article
    DOI: 10.1177/0883911506076045
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2007
    detail.hit.zdb_id: 2073790-7
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  • 3
    Online Resource
    Online Resource
    Novel Polyamide 6,10 Variants Synthesized by Modified Interfacial Polymerization for Application as a Rate-Modulated Monolithic Drug Delivery System
    SAGE Publications ; 2007
    In:  Journal of Bioactive and Compatible Polymers Vol. 22, No. 3 ( 2007-05), p. 281-313
    Details
    In: Journal of Bioactive and Compatible Polymers, SAGE Publications, Vol. 22, No. 3 ( 2007-05), p. 281-313
    Abstract: The aim of this study was to explore and elucidate the possibility of employing an aliphatic polyamide 6,10 (PA 6,10) synthesized by a modified interfacial polymerization process as a novel rate-modulated monolithic matrix drug delivery system. A Plackett—Burman experimental design was used to synthesize 14 different PA 6,10 polymers using the interfacial polymerization process of synthesis comprising the monomers namely hexamethylenediamine and sebacoyl chloride and the solvents namely hexane (nonpolar phase) and deionized water (polar phase). This process was modified by variations in stoichiometry of monomers, volume ratios of solvents as well as solvent phase modification using cyclohexane and sodium hydroxide for the nonpolar and polar solvent phases, respectively. The micromechanical parameters of the newly synthesized PA 6,10 variants were elucidated in terms of the matrix resilience (MR), matrix hardness and deformation energy, in which case matrix hardness and deformation energy were expressed as second-order polynomial hydration rate constants. The effect of changes in pH of the hydration media on these parameters was also explored as part of the characterization process. Scanning electron microscopy and Fourier transform infrared spectroscopy were used to correlate the effect of synthesis variables on the micromechanical behavior PA 6,10 and its subsequent ability to impact drug release. The micromechanical values revealed that all independent formulation variables had a significant influence on the responses. Furthermore, the applied statistical model was utilized in selecting a combination of reaction variables to produce optional physicomechanical properties. The MR was selected for optimization among other parameters since it had a prominent effect on matrix integrity as well as drug release. The one-way analysis of variance, comparison of experimental versus fitted data, the R 2 and P-values as well as the Durbin—Watson statistic indices were used in ascertaining the accuracy of the model. The rate-modulating drug release ability of synthetic aliphatic PA 6,10 was explored to direct the optimization using a higher resolution Box—Behnken statistical design. Constraints were set to obtain levels of independent variables that optimized the physicomechanical properties and the mean dissolution time fixed at eight hours.
    Type of Medium: Online Resource
    ISSN: 0883-9115 , 1530-8030
    URL: Article
    DOI: 10.1177/0883911507078269
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2007
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  • 4
    Online Resource
    Online Resource
    Encapsulation of Essential Oils within a Polymeric Liposomal Formulation for Enhancement of Antimicrobial Efficacy
    SAGE Publications ; 2010
    In:  Natural Product Communications Vol. 5, No. 9 ( 2010-09), p. 1934578X1000500-
    Details
    In: Natural Product Communications, SAGE Publications, Vol. 5, No. 9 ( 2010-09), p. 1934578X1000500-
    Abstract: Essential oils and their constituents are known to possess antimicrobial activity; however, their inherent volatility is a limiting factor. In order to exploit the antimicrobial efficacy of essential oils, encapsulation within polymeric liposomal systems was undertaken. The liposomes were subsequently polymer-coated in order to further enhance the stability of the formulations. Essential oils distilled from Artemisia Afra, Eucalyptus Globulus and Melaleuca alternifolia were encapsulated into diastearoyl phosphatidylcholine and diastearoyl phosphatidylethanolamine liposomes employing a reverse phase evaporation methodology. A polyelectrolyte coating was then applied via the layer-by-layer self-deposition technique. A batch of the liposomes was polymer-coated with a 0.15%w/v chitosan solution. Using the minimum inhibitory concentration assay, the liposome-encapsulated, unencapsulated and polymer-coated liposome-encapsulated essential oils were compared in order to observe whether the antimicrobial efficacy was improved with encapsulation and polymer coating. Fractional inhibitory concentrations (FICs) were calculated in order to determine the antimicrobial interactions amongst the lipoid components, polymer coating and essential oils (synergistic, additive, indifferent and antagonistic interactions). With the exception of A. afra, microbial growth was inhibited at lower concentrations for the encapsulated formulations in comparison with the non-encapsulated oils. Synergistic to additive interactions were noted for encapsulated E. globulus (ΣFIC values 0.25-0.45) and M. alternifolia (ΣFIC values 0.26-0.52) formulations. The addition of the polymer coating did not enhance antimicrobial activity, but owing to their positive effects on membrane stability, its presence is important as a means of extending the shelf life of these formulations. Additionally, the presence of the polymeric coating availed the essential oil at a slower rate. This investigation is a stepping stone towards the promotion of the antimicrobial use of essential oils. The added benefits are that essential oils not only provide effective antimicrobial efficacy, but also promote a “greener” consumerism. Within liposomes, they will enhance dermato-cosmetic properties and increase the marketing image of the final product.
    Type of Medium: Online Resource
    ISSN: 1934-578X , 1555-9475
    URL: Article
    DOI: 10.1177/1934578X1000500912
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2010
    detail.hit.zdb_id: 2430442-6
    SSG: 15,3
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  • 5
    Online Resource
    Online Resource
    A Novel Salted-out and Subsequently Crosslinked Poly(Lactic-co-Glycolic Acid) Polymeric Scaffold Applied to Monolithic Drug Delivery
    SAGE Publications ; 2008
    In:  Journal of Bioactive and Compatible Polymers Vol. 23, No. 2 ( 2008-03), p. 132-153
    Details
    In: Journal of Bioactive and Compatible Polymers, SAGE Publications, Vol. 23, No. 2 ( 2008-03), p. 132-153
    Abstract: This study involved a statistical approach to develop a mechanistic understanding of the salting-out of poly(lactic-co-glycolic acid) (PLGA) and to evaluate the capacity to modulate the physicochemical and physicomechanical properties of PLGA by incorporating electrolytes that produce stochastic fluctuations. The correlation between the three types of salts used and the extent of PLGA chain transitions were established by structural-thermal analysis. Drug-loaded monolithic matrices are prepared by direct compressing salted-out PLGA and a model drug (melatonin). PLGA scaffolds possess fiber diameters and volumes ranging between 0.1—15 μm and 0.0075—14,000 μm 3 , respectively. Texture profile analysis reveal a significant increase in the energy absorbed and matrix resilience with increased NaCl 2 and AlCl 3 concentrations. In vitro drug release studies were performed in phosphate buffered saline (pH 7.4; 37°C); the release media was sampled at pre-determined intervals and analyzed by UV spectroscopy. Ideal zero-order drug release profiles were observed with 20% melatonin over a 30-day period. Monolithic matrices prepared by crosslinking melatonin with PLGA reveal a superior capability to control drug release. The salting-out and subsequent crosslinking of PLGA significantly modified the physicochemical and physicomechanical properties of native PLGA and demonstrated the ability to achieve controlled drug release.
    Type of Medium: Online Resource
    ISSN: 0883-9115 , 1530-8030
    URL: Article
    DOI: 10.1177/0883911507088274
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2008
    detail.hit.zdb_id: 2073790-7
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