Dendrimers Bind Human Serum Albumin

Abstract

Dendrimers are synthetic, highly branched, spherical macromolecules with nanometer dimensions and potential applications in DNA and drug delivery systems. Human serum albumin (HSA) is a major transporter for delivering several endogenous compounds and drugs in vivo. The aim of this study was to examine the interaction of human serum albumin with several dendrimers such as mPEG-PAMAM (G3), mPEG-PAMAM (G4), and PAMAM (G4) at physiological conditions, using constant protein concentration and various dendrimer compositions. FTIR, UV-visible, CD, and fluorescence spectroscopic methods were used to analyze macromolecule binding mode, the binding constant and the effects of dendrimers complexation on HSA stability and conformation. Structural analysis showed that dendrimers bind HSA via polypeptide polar groups (hydrophilic) with number of bound polymer (n) 1.08 (mPEG-PAMAM-G3), 1.50 (mPEG-PAMAM-G4), and 0.96 (PAMAM-G4). The overall binding constants estimated were of KmPEG-G3=1.3 (+/-0.2)x10(4) M(-1), KmPEG-G4=2.2 (+/-0.4)x10(4) M(-1), and KPAMAM-G4=2.6 (+/-0.5)x10(4) M(-1). HSA conformation was altered by dendrimers with a major reduction of alpha-helix and increase in random coil and turn structures suggesting a partial protein unfolding.

Multi-Target Inhibition of Cancer Cell Growth by SiRNA Cocktails and 5-Fluorouracil Using Effective Piperidine-Terminated Phosphorus Dendrimers

“…However, we can make an assumption that an excess of dendrimers' positive charges is crucial for the effective transfection, not only due to promoted cell entry, but is also related to the interactions with serum proteins. Positively charged dendrimers tend to associate with serum proteins, including serum albumins [48][49][50] and regulatory proteins [51,52]. On one hand, this can reduce dendrimers' cytotoxicity since their surface functional groups might be shielded by proteins.…”

Multiscale Modeling for Host-Guest Chemistry of Dendrimers in Solution

“…The binding strength between dendrimer-guest complexes has been determined by isothermal titration calorimetry(ITC) [26][27][28][29], high performance liquid chromatography (HPLC) [30] and fluorescence spectroscopy [31][32][33]. Detailed conformations of dendrimers interacting with guest molecules have been studied by nuclear magnetic resonance(NMR) [34][35][36] and the size of the dendrimer-guest complexes has been measured by dynamic light scattering (DLS) [22,31].…”

Effect of Synthetic Polymers on tRNA Nanoparticle Formation

“…Synthetic polymer complexes with DNA and tRNA via hydrophilic, hydrophobic contacts, groove binding and phosphate interaction [25][26][27][28][29]. The infrared spectra and difference spectra of the free tRNA showed major alterations of tRNA in-plane vibrations and the backbone phosphate asymmetric and symmetric stretching bands [30][31][32][33][34][35], upon polymer complexation ( Figure 2-panels A and B). Low concentration (0.125 mM) of synthetic polymers PEG-3350, PEG-6000, mPEG-PAMAM-G3, mPEG-PAMAM-G4 and PAMAM-G4 induced minor changes of tRNA vibrational frequencies, while at high polymer content (1 mM) major alterations of tRNA inplane and the backbone vibrational frequencies (Figure 2-panels A and B).…”