Publication Type Journal Article
Title Evaluation of electrostatic binding of PAMAM dendrimers and charged phthalocyanines by fluorescence correlation spectroscopy
Authors Emilio Garcia-Fernandez Pedro M. R. Paulo Sílvia M. B. Costa
Groups MPPM
Journal PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Year 2015
Month
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Volume 17
Number 6
Pages 4319-4327
Abstract We have assessed host-guest interactions between PAMAM dendrimers and charged phthalocyanine probes by Fluorescence Correlation Spectroscopy (FCS). Our results show strong binding in water at low ionic strength with an affinity that decreases from K-B similar to 10(9) to 10(8) M-1 upon decreasing the phthalocyanine charge of z = -4, -2 and -1. The binding affinity also decreases significantly upon salt addition leading to KB values of ca. 10(5)-10(6) M-1. The changes of binding affinity probed by varying the phthalocyanine charge, and by changing the ionic strength or pH conditions, allowed us to evaluate the electrostatic contribution (K-el) in dendrimer-phthalocyanine interactions. In particular, this approach afforded values of electrostatic potential for PAMAM dendrimers in water at low ionic strength and at dendrimer concentrations in the nanomolar range. The electrostatic potential of PAMAM generations 4 and 7 are around 50 mV in close agreement with theoretical estimates using the Poisson-Boltzmann cell model. Interestingly, the nonelectrostatic binding is significant and contributes even more than electrostatic binding to dendrimer-phthalocyanine interactions. The nonelectrostatic binding contributes to an affinity of KB above 10(5) M-1, as measured under conditions of low dendrimer charge and high ionic strength, which makes these dendrimers promising hosts as drug carriers.
DOI http://dx.doi.org/10.1039/c4cp05373g
ISBN
Publisher ROYAL SOC CHEMISTRY
Book Title
ISSN 1463-9076
EISSN 1463-9084
Conference Name
Bibtex ID ISI:000349005900041
Observations
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