Amphiphilic drug persuaded collapse of polyvinylpyrrolidone and poly(ethylene glycol) chains: A dynamic light scattering study

Light scattering has proved to be useful in characterizing colloidal systems. We have studied the interaction between an amphiphilic drug, amitriptyline hydrochloride (AMT), and neutral polymers, polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG), using the dynamic light scattering (DLS) technique. AMT was found to interact with PVP more strongly than PEG. A large decrease of the size of aggregates upon increase of AMT concentration indicates a successive collapse of the polymer conformation. The partial negatively charged oxygen atoms, present in the amide group of PVP, were believed to be responsible for the collapse while interacting with the cationic head group of AMT. Presence of NaBr in the solution enhanced the effect markedly and made the AMT–PVP aggregates more compact. The PEG aggregates also showed a similar behavior, although less pronounced than the PVP. The results obtained in the present investigations may be helpful to design the drug delivery systems for the antidepressant drugs as the higher concentration of these drugs is harmful for the human body. Likewise, as the results have shown that on increasing the temperature there is a decrease in the extent of interaction; this may be helpful for the controlled release formulations.