Bolaamphiphilic Bis-Dehydropeptide Hydrogels as Potential Drug Release Systems

Abstract

<div>The self-assembly of nanometric structures from molecular building blocks is an effective</div><div>way to make new functional materials for biological and technological applications. In this work</div><div>four symmetrical bolaamphiphiles based on dehydrodipeptides</div><div>(phenylalanyldehydrophenylalanine and tyrosyldehydrophenylalanine) linked through phenyl</div><div>or naphthyl linkers (terephthalic acid and 2,6-naphthalenedicarboxylic acid) were prepared and</div><div>their self-assembly properties studied. The results showed that all compounds with the exception</div><div>of the bolaamphiphile of tyrosyldehydrophenylalanine and 2,6-naphthalene dicarboxylic acid</div><div>gave self-standing hydrogels with critical gelation concentrations of 0.3 and 0.4 wt% using a pH</div><div>trigger. The self-assembly of these hydrogelators was investigated using STEM microscopy,</div><div>which revealed a network of entangled fibres. According to rheology the dehydrodipeptide</div><div>bolaamphiphile hydrogelators are viscoelastic materials with an elastic modulus G’ that falls in</div><div>the range of native tissue (0.37 kPa brain – 4.5 kPa cartilage). In viability and proliferation studies,</div><div>it was found that these compounds were non-toxic towards the human keratinocyte cell line,</div><div>HaCaT. In sustained release assays, we studied the effects of the charge present on the model</div><div>drug compound on the rate of cargo release from the hydrogel networks. Methylene blue (MB),</div><div>methyl orange (MO) and ciprofloxacin were chosen as cationic, anionic and overall neutral cargo,</div><div>respectively. These studies have shown that the hydrogels provide a sustained release of methyl</div><div>orange and ciprofloxacin, while the methylene blue is retained by the hydrogel network.</div>