Interaction of Dendrimers (Artificial Proteins) with Biological Hydroxyapatite Crystals

Abstract

This investigation sets out to mimic protein-crystal interaction during biomineralization with the use of artificial proteins (dendrimers). It is hypothesized that these interactions depend on the surface charge of hydroxyapatite crystals. This was investigated with the use of dendrimers with capped surfaces of different charges to probe the surface. We used AFM images of crystal-bound dendrimers to determine the distribution of the surface charge, and its magnitude was correlated to the binding capacity of the dendrimers to the surface. The binding capacity of the dendrimers in ascending order at pH 7.4 was: acetamide-capped, -NHC(O)CH3, neutral charge; carboxylic-acid-capped, -COOH, negative charge; and amine-capped, -NH2, positive charge. AFM images of the crystals showed dendrimers spaced equally along the crystal. The results suggest that the crystal surface has alternating bands of positive and negative charge or a differential charge array, i.e., alternating bands of either more or less positive or negative charge.

Effects of glutamic acid shelled PAMAM dendrimers on the crystallization of calcium phosphate in diffusion systems

“…In this study, the average graft ratio was 72%. The terminii of -COOH and -NH 2 at pH 7.4 are negatively and positively charged, respectively [15]. The 100 and 010 surface of OCP are mostly positive and negative, respectively, according to the structure of OCP [34].…”

“…Moreover, PAMAM G3.5 was used to prepare a CaCO 3 /poly(ethylenimine) composite film, whereas without any PAMAM or with PAMAM G1.5, composite films could not be formed [14]. Recently, PAMAM with different termini were used to investigate the interaction between protein and hydroxyapatite (Ca 5 (PO 4 ) 3 OH, HAP) [15,16] and the synthesis of nanocrystalline (nano)-HAP [17][18][19]. PAMAM with terminal groups of -NHC(O)CH 3 , -COOH, and -NH 2 were used as probes to study the alternating bands of charge distribution of natural enamel HAP crystals [15].…”

“…Recently, PAMAM with different termini were used to investigate the interaction between protein and hydroxyapatite (Ca 5 (PO 4 ) 3 OH, HAP) [15,16] and the synthesis of nanocrystalline (nano)-HAP [17][18][19]. PAMAM with terminal groups of -NHC(O)CH 3 , -COOH, and -NH 2 were used as probes to study the alternating bands of charge distribution of natural enamel HAP crystals [15]. Zhou et al found that the morphology and size of HAP were affected differently by carboxylic-terminated PAMAM and by polyhydroxyterminated PAMAM under hydrothermal treatment due to the different nucleation sites and adsorption onto the crystal surface [18].…”

Study on enhanced lymphatic exposure of polyamidoamin-alkali blue dendrimer for paclitaxel delivery and influence of the osmotic pressure on the lymphatic targeting

“…Dendrimers with a number of synthetic scaffolds have previously been shown to promote passive tumor targeting via the enhanced permeation and retention effect (Tomalia et al, 2007;Lei et al, 2008;Lim et al, 2009). Due to similarities in size and highly branched, monodisperse three dimensional globular structure in nanometer scale, dendrimers have, in several instances, been referred to as ''artificial proteins'' (Tam & Spetzler, 2001;Chen et al, 2003). Consequently, dendrimers have the potential to exhibit similar physicochemical properties to proteins but to show improved stability to conditions that would otherwise promote rapid and uncontrolled degradation.…”

Synthesis of a novel polyamidoamine dendrimer conjugating with alkali blue as a lymphatic tracer and study on the lymphatic targeting in vivo

“…Dendrimers with a number of synthetic scaffolds have previously been shown to promote passive tumor targeting via the enhanced permeation and retention effect (Tomalia et al, 2007;Lei et al, 2008;Lim et al, 2009). Due to similarities in size and highly branched, monodisperse three dimensional (3D) globular structure in nanometer scale, dendrimers have, in several instances, been referred to as ''artificial proteins'' (Tam & Spetzler, 2001;Chen et al, 2003). Consequently, dendrimers have the potential to exhibit similar physicochemical properties to proteins but to show improved stability to conditions that would otherwise promote rapid and uncontrolled degradation.…”