Solubility of nicotinic acid in polyamidoamine dendrimer solutions

In the present study we investigated the effect of ethylenediamine (EDA) core polyamidoamine (PAMAM) dendrimers on the aqueous solubility of nicotinic acid. The aqueous solubility of nicotinic acid was measured in the presence of dendrimers at room temperature in distilled water. The effect of variables, such as pH condition, concentration, surface functional group and generation (molecule size) of dendrimer, has been investigated. Results showed that the solubility of nicotinic acid in the dendrimer solutions was proportional to dendrimer concentration, both amine and ester-terminated dendrimers caused the higher increase in nicotinic acid solubility at higher pH conditions. The order in which the dendrimers increased the solubility at a constant pH condition was G4 > G3 > G2 > G1. In addition, at each pH, the solubility of nicotinic acid was greater in the presence of amine-terminated dendrimers compared to the amine ester-terminated dendrimers possessing the same number of surface functional groups. Under suitable conditions PAMAM dendrimers can be highly effective used to enhance the solubility of nicotinic acid.