Anal Bioanal Chem (2014) 406:455–458 DOI 10.1007/s00216-013-7458-0
NOTE
Analysis of polyamidoamine dendrimers by isoelectric focusing Samik K. Upadhaya & Douglas R. Swanson & Donald A. Tomalia & Ajit Sharma
Received: 3 September 2013 / Revised: 17 October 2013 / Accepted: 22 October 2013 / Published online: 19 November 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract Polyamidoamine dendrimers have been studied extensively for their potential applications in nanomedicine. Their uses as imaging, drug, and nucleic acid delivery agents are nearing clinical trials. As such, characterization of polyamidoamine dendrimers and their nano-devices is of immense importance for monitoring the efficiency of their synthesis, purity, and quality control of manufactured products as well as their in vivo behavior. We report here the analysis of polyamidoamine dendrimers possessing various cores and surface groups with a simple and inexpensive isoelectric focusing method. The isoelectric points of the dendrimers were readily determined from a calibration plot generated by running proteins with known pI values. The isoelectric points for various surface-modified polyamidoamine dendrimers ranged from 4 to 9. Polyamidoamine dendrimers possessing terminal hydroxyl groups gave a pI >7, while those with terminal carboxyl groups exhibit a pI 9 to 6.5 [4]. Succinylation of the dendrimer to lower its pI not only made the nano-device more biocompatible but it also dramatically altered its uptake by various organs in mice.
Conclusion IEF offers a facile and inexpensive procedure for separating and characterizing PAMAM dendrimers. It not only provides additional evidence for their unique behavior as “protein mimics,” but also offers an important new tool for characterizing PAMAM dendrimers. A number of surface functionalized dendrimers are currently used in a variety of nano-medical applications [1, 2]. It is readily apparent that the isoelectric points obtained for various surface-modified PAMAM dendrimers span a wide pI range of 4–9 and are equivalent to specific pIs associated with in vivo cellular versus blood proteins found in a human. As such, this information should prove invaluable for engineering and designing appropriate biocompatible or functional dendrimer surface groups for in vivo use. This would clearly accelerate and facilitate their utilization as either protein mimics or dendrimer-based nano-devices in a variety of proposed in vivo medical applications.
References 1. Tomalia DA, Christensen JB, Boas U (2012) Dendrimers, dendrons and dendritic polymers: discovery, applications, and the future. Cambridge University Press, New York 2. Fréchet JMJ, Tomalia DA (2001) Dendrimers and other dendritic polymers. Wiley, New York 3. Sharma A, Desai A, Ali AR (2005) J Chromatogr A 1081:238–244 4. Sato N, Park CW, Kim H et al (2003) Nucl Med Biol 30:617–625 5. Copeland RA (1994) Methods for protein analysis a practical guide to laboratory protocols. Chapman and Hall, London
NOTE
Analysis of polyamidoamine dendrimers by isoelectric focusing Samik K. Upadhaya & Douglas R. Swanson & Donald A. Tomalia & Ajit Sharma
Received: 3 September 2013 / Revised: 17 October 2013 / Accepted: 22 October 2013 / Published online: 19 November 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract Polyamidoamine dendrimers have been studied extensively for their potential applications in nanomedicine. Their uses as imaging, drug, and nucleic acid delivery agents are nearing clinical trials. As such, characterization of polyamidoamine dendrimers and their nano-devices is of immense importance for monitoring the efficiency of their synthesis, purity, and quality control of manufactured products as well as their in vivo behavior. We report here the analysis of polyamidoamine dendrimers possessing various cores and surface groups with a simple and inexpensive isoelectric focusing method. The isoelectric points of the dendrimers were readily determined from a calibration plot generated by running proteins with known pI values. The isoelectric points for various surface-modified polyamidoamine dendrimers ranged from 4 to 9. Polyamidoamine dendrimers possessing terminal hydroxyl groups gave a pI >7, while those with terminal carboxyl groups exhibit a pI 9 to 6.5 [4]. Succinylation of the dendrimer to lower its pI not only made the nano-device more biocompatible but it also dramatically altered its uptake by various organs in mice.
Conclusion IEF offers a facile and inexpensive procedure for separating and characterizing PAMAM dendrimers. It not only provides additional evidence for their unique behavior as “protein mimics,” but also offers an important new tool for characterizing PAMAM dendrimers. A number of surface functionalized dendrimers are currently used in a variety of nano-medical applications [1, 2]. It is readily apparent that the isoelectric points obtained for various surface-modified PAMAM dendrimers span a wide pI range of 4–9 and are equivalent to specific pIs associated with in vivo cellular versus blood proteins found in a human. As such, this information should prove invaluable for engineering and designing appropriate biocompatible or functional dendrimer surface groups for in vivo use. This would clearly accelerate and facilitate their utilization as either protein mimics or dendrimer-based nano-devices in a variety of proposed in vivo medical applications.
References 1. Tomalia DA, Christensen JB, Boas U (2012) Dendrimers, dendrons and dendritic polymers: discovery, applications, and the future. Cambridge University Press, New York 2. Fréchet JMJ, Tomalia DA (2001) Dendrimers and other dendritic polymers. Wiley, New York 3. Sharma A, Desai A, Ali AR (2005) J Chromatogr A 1081:238–244 4. Sato N, Park CW, Kim H et al (2003) Nucl Med Biol 30:617–625 5. Copeland RA (1994) Methods for protein analysis a practical guide to laboratory protocols. Chapman and Hall, London
