Figure 6.

All the error bars represent the standard deviation of three separate measurements. Where error bars are not evident, they are smaller than the symbol. The solid line represents the theoretical maximal amount of SMD that would diffuse from the hydrogel into the extra volume of PBS if there were no obstruction to diffusion. (a) Elution of naltrexone (2 mM) from different concentrations of peptide 1A hydrogels (20–40 mM) and different peptide hydrogels (1A, 1B, 1C) at 25 °C. There is essentially no difference in naltrexone elution under these conditions. That the elution of naltrexone is less than the theoretical maximal elution for the first four samples does not necessarily imply there is interaction between naltrexone and the peptide fibril – a longer elution time before sampling will likely result in much a closer fit with theoretical maximal elution. (b) Elution of naltrexone (0.67 mg/g), methotrexate (0.89 mg/g), and doxorubicin (1.06 mg/g) from peptides 1A and 1B. The values in brackets correspond to the drug loading capacities of SMDs (2 mM) in the peptide hydrogels (20 mM). (c) Comparison of the time-dependent release of naltrexone and doxorubicin (2 mM each) from peptides 1A and 1B hydrogels (20 mM). The time points are 0.25 h, 0.50 h, 1 h, 2 h, 4 h, 8 h, 16 h, and 24 h. The graph shows that there was burst release of SMDs from the hydrogels, but the extent of release depends on the peptide-SMD combination. All the results indicate that the elution of SMDs depends both on the C-terminal residue (Xaa) of the peptide and the nature of the SMD.