Molecular Imprinted Hydrogels in Drug Delivery Applications
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eleased from the hydrogel matrix over the specified amount of time. The results are given in Figure 1. For the second set of samples, a hydrogel substrate was polymerized with no addition of the drug. A second layer of the hydrogel was polymerized with double the concentration of drug in the surface layer as in the samples from the initial set. The molar ratio of drug used in each set of samples was equal. After polymerization, the material was placed into distilled water for twelve hours, which was also tested using UV-Visible spectroscopy to determine the concentration of drug released over the specified amount of time. The results for the surface treated hydrogel samples are given in Figure 2. A comparison of the absorbance of drug released from the sample groups is given in Figure 3. The concentration was calculated using the Beer-Lambert Law given in equation 1. (1)
=ԑ
In equation 1, A represents the absorbance, ԑ represents the molar attenuation coefficient, c represents the molar concentration of the target molecules in solution, and l represents the path length. The molar attenuation coefficient was calculated by measuring the absorbance of a known concentration of drug in distilled water, while the path length used is standard and equal to 1 cm. Therefore the concentration of the drug in the distilled water solution is directly proportional to the absorbance. The test results for the reversibility testing revealed that the extracted concentration of drug was 10% of the first delivery. This result was consistent across samples and remained constant after the initial drug extraction.
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Wavelength (nm)
Figure 1. A sample from the first set, which included the drug dispersed in the matrix.
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Wabvelength (nm)
Figure 2. A sample from the second set, where the drug was imprinted on the surface only.
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Surface
Figure 3. A comparison of the absorbance of the released drug between the two imprinting methods.
CONCLUSION The goal of this project was to determine whether pH-responsive hydrogels could prove beneficial as potential materials for drug delivery applications. The drug release action occurred as a result of the swelling in response to the change in pH. Furthermore, the goal was to determine how the mass transfer varies as a function of drug distribution through the polymer matrix. After a span of twelve hours, the material with the surface coating had a much higher concentration of drug released into solution than the material with the drug dispersed, as shown in Figure 3. Nearly all of the drug was released from the surface modified samples, while a higher concentration of drug was retained in the matrix for the samples with drug dispersed throughout the matrix. For the design of drug delivery materials, the prolonged release may play a role in creating an optimized material. The drug delivery after reintroduc
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