A Study of Diffusion in Agar Gels by a Light Absorption Method

Felicetta, Vincent F.; Markham, Aaron E.; Peniston, Quintin P.; McCarthy, Joseph L.

doi:10.1021/ja01176a089

Cited by 35 publications

(10 citation statements)

References 4 publications

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“…The fitting was performed using the software GraphPad Prism 5.0 (La Jolla, CA, USA). The imperfect interface between the gel phases at t = 0 was corrected by assuming that the error in the apparent diffusivity is proportional to the error in time as previously described. , …”

Section: Methodsmentioning

confidence: 99%

“…The imperfect interface between the gel phases at t = 0 was corrected by assuming that the error in the apparent diffusivity is proportional to the error in time as previously described. 37,43 Capillary Electrophoresis Frontal Analysis (CE-FA). Development of the CE-FA binding methods was based on a previous study involving the naphthylamide model compounds.…”

Section: Molecular Pharmaceuticsmentioning

confidence: 99%

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Role of Electrostatic Interactions on the Transport of Druglike Molecules in Hydrogel-Based Articular Cartilage Mimics: Implications for Drug Delivery

Baldursdóttir

Hvidt

et al. 2016

Mol. Pharmaceutics

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In the field of drug delivery to the articular cartilage, it is advantageous to apply artificial tissue models as surrogates of cartilage for investigating drug transport and release properties. In this study, artificial cartilage models consisting of 0.5% (w/v) agarose gel containing 0.5% (w/v) chondroitin sulfate or 0.5% (w/v) hyaluronic acid were developed, and their rheological and morphological properties were characterized. UV imaging was utilized to quantify the transport properties of the following four model compounds in the agarose gel and in the developed artificial cartilage models: H-Ala-β-naphthylamide, H-Lys-Lys-β-naphthylamide, lysozyme, and α-lactalbumin. The obtained results showed that the incorporation of the polyelectrolytes chondroitin sulfate or hyaluronic acid into agarose gel induced a significant reduction in the apparent diffusivities of the cationic model compounds as compared to the pure agarose gel. The decrease in apparent diffusivity of the cationic compounds was not caused by a change in the gel structure since a similar reduction in apparent diffusivity was not observed for the net negatively charged protein α-lactalbumin. The apparent diffusivity of the cationic compounds in the negatively charged hydrogels was highly dependent on the ionic strength, pointing out the importance of electrostatic interactions between the diffusant and the polyelectrolytes. Solution based affinity studies between the model compounds and the two investigated polyelectrolytes further confirmed the electrostatic nature of their interactions. The results obtained from the UV imaging diffusion studies are important for understanding the effect of drug physicochemical properties on the transport in articular cartilage. The extracted information may be useful in the development of hydrogels for in vitro release testing having features resembling the articular cartilage.

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Section: Methodsmentioning

confidence: 99%

Section: Molecular Pharmaceuticsmentioning

confidence: 99%

Role of Electrostatic Interactions on the Transport of Druglike Molecules in Hydrogel-Based Articular Cartilage Mimics: Implications for Drug Delivery

Baldursdóttir

Hvidt

et al. 2016

Mol. Pharmaceutics

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“…By plotting the diffusion coefficient as a function of the reciprocal of time (Fig. 9B), the apparent diffusion coefficient was obtained from the intercept of the straight line with the y-axis [21,51]. The diffusion coefficient was determined to be (6.3 ± 0.05) × 10 -10 m 2 /s, (6.9 ± 0.05) × 10 -10 m 2 /s and (7.5 ± 0.11) × 10 -10 m 2 /s (n = 3 × 3) at 22.0 ± 1.0 °C using the D100, SDI and D100 system with the line rotated 90°, respectively.…”

Section: Lidocaine Diffusion In Hydrogelmentioning

confidence: 99%

Performance characteristics of UV imaging instrumentation for diffusion, dissolution and release testing studies

Jensen

Goodall

et al. 2016

Journal of Pharmaceutical and Biomedical Analysis

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UV imaging is capable of providing spatially and temporally resolved absorbance measurements, which is highly beneficial in drug diffusion, dissolution and release testing studies. For optimal planning and design of experiments, knowledge about the capabilities and limitations of the imaging system is required. The aim of this study was to characterize the performance of two commercially available UV imaging systems, the D100 and SDI. Lidocaine crystals, lidocaine containing solutions, and gels were applied in the practical assessment of the UV imaging systems. Dissolution of lidocaine from single crystals into phosphate buffer and 0.5% (w/v) agarose hydrogel at pH 7.4 was investigated to shed light on the importance of density gradients under dissolution conditions in the absence of convective flow. In addition, the resolution of the UV imaging systems was assessed by the use of grids. Resolution was found to be better in the vertical direction than the horizontal direction, consistent with the illumination geometry. The collimating lens in the SDI imaging system was shown to provide more uniform light intensity across the UV imaging area and resulted in better resolution as compared to the D100 imaging system (a system without a lens). Under optimal conditions, the resolution was determined to be 12.5 and 16.7 line pairs per mm (lp/mm) corresponding to line widths of 40μm and 30μm in the horizontal and vertical direction, respectively. Overall, the performance of the UV imaging systems was shown mainly to depend on collimation of light, the light path, the positioning of the object relative to the line of 100μm fibres which forms the light source, and the distance of the object from the sensor surface.

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“…1, higher values of tracer-diffusion coefficient at very low concentrations suggest that ion-solvent structure in aqueous solution and that in gel medium are not the same due to gel-water interactions. The gel has a capacity to hold up water molecules by hydrogen bonding, adsorption [13] and dipole-dipole interactions [14]. Thus, the presence of gel affects dipole association in water which causes distortion in the structure of water.…”

Section: Methodsmentioning

confidence: 99%

Tracer-diffusion of H₂ ³²PO₄ ^¯ Ions in Electrolyte Solutions in Agar Gel Medium

Baluja

Shukla

1984

Radiochimica Acta

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The tracer-diffusion coefficients of H^'PO, ions have been determined in sodium and potassium nitrate solutions immobilized in 2.5 % agar gel over the concentration range 10"' -1.0 Μ at 298 K. Comparison of the experimental and theoretical values indicates failure of the Onsager-Fuoss theory at higher concentrations of electrolyte solutions. The observed results are explained on the basis of water-gel, ion-water and ion-ion interactions. Diffusion rates are also determined at various gel concentrations at different temperatures (298 -323 K), keeping the electrolyte (KNO,) concentration constant at 10"' M. The obstruction effect of gel calculated in terms of formation factor F is observed to increase with increasing gel concentration. The results are explained on the basis of EYRING's theory of diffusion. centage was varied from 0.5-5.0%, keeping the electrolyte concentration constant at 10" 2 M. After the gel had set, both ends of the tube were tightly corked and kept in an automatically regulated thermostat at the desired temperature.After allowing the diffusion to proceed for a definite time (24 hrs), the gel columns on both sides of the zone were sliced into 0.5 cm samples. These samples were carefully transferred to aluminium planchettes and dehydrated in a hot air oven at 65 °C. The radioactivity in each sample was counted by an end window Geiger-Muller counter under the conditions of constant geometry.

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A Study of Diffusion in Agar Gels by a Light Absorption Method

Cited by 35 publications

References 4 publications

Role of Electrostatic Interactions on the Transport of Druglike Molecules in Hydrogel-Based Articular Cartilage Mimics: Implications for Drug Delivery

Role of Electrostatic Interactions on the Transport of Druglike Molecules in Hydrogel-Based Articular Cartilage Mimics: Implications for Drug Delivery

Performance characteristics of UV imaging instrumentation for diffusion, dissolution and release testing studies

Tracer-diffusion of H₂ ³²PO₄ ^¯ Ions in Electrolyte Solutions in Agar Gel Medium

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A Study of Diffusion in Agar Gels by a Light Absorption Method

Cited by 35 publications

References 4 publications

Role of Electrostatic Interactions on the Transport of Druglike Molecules in Hydrogel-Based Articular Cartilage Mimics: Implications for Drug Delivery

Role of Electrostatic Interactions on the Transport of Druglike Molecules in Hydrogel-Based Articular Cartilage Mimics: Implications for Drug Delivery

Performance characteristics of UV imaging instrumentation for diffusion, dissolution and release testing studies

Tracer-diffusion of H2 32PO4 ¯ Ions in Electrolyte Solutions in Agar Gel Medium

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Tracer-diffusion of H₂ ³²PO₄ ^¯ Ions in Electrolyte Solutions in Agar Gel Medium