Dendrimers are a special class of polyelectrolytes, which are characterized by their densely branched and well-defined spherical geometry. Amino-terminal dendrimers resemble spheres, whose uniform surface charge densities can be continuously modulated by pH or ionic strength. Dendrimers have a wide range of applications, including biomedical applications such as drug delivery, gene delivery, cancer therapy and diagnostic agents. Their unique properties originate in their macromolecular structure. It is known that dendrimers can undergo irreversible swelling, and this process is directly connected to the degree of protonation of dendrimer molecules. The hydration of dendrimer films seems to be a crucial aspect of their implementation. In all biological systems, the conformational stability is intrinsically connected with natural hydration. Therefore, the estimation of the degree of hydration in dendrimer films on a model surface is essential for the study of their potential applications. The present study focuses on the structure of dendrimer monolayers on gold surfaces. We used multi parametric surface plasmon resonance (MP-SPR) and a quartz crystal microbalance with dissipation energy monitoring (QCM-D) to investigate the conformational behaviour of the 6th generation of PAMAM molecules. The combination of MP-SPR and QCM-D measurements allows the investigation of factors that govern the immobilization of PAMAM dendrimers on a gold coated sensor surface. Changes in pH have a strong effect on the binding affinity of the polymer to the surface and additionally, indicate very different conformation behaviours. The trends in the binding affinity and the surface saturation amount correspond well with the degree of change of protonation of the adsorbed molecules. This data very clearly indicates how the structure of the dendrimer can influence the properties of the polymer film formed on the gold surface. PAMAM films on gold surfaces are composed of 80% water. This is a particularly large value compared to the amount of water associated with the dendrimer molecules during the swelling process, which was estimated at 25-30%. This is one of the additional advantages of dendrimeric systems. These investigations lead to a more profound understanding of the self-assembling behaviour of branched polyelectrolytes, which are interesting candidates for reversibly tunable swelling materials for drug delivery or smart molecules for surface functionalization.

Physicochemical characterisation of PAMAM dendrimer as multifunctional nanocarriers

2019 Spring National Meeting

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