Use of poly(amidoamine) drug conjugates for the delivery of antimalarials to Plasmodium Patricia Urbán a,b,c , Juan José Valle-Delgado a,b,c , Nicolò Mauro d , Joana Marques a,b,c , Amedea Manfredi d , Matthias Rottmann e , Elisabetta Ranucci d , Paolo Ferruti d , Xavier Fernàndez-Busquets a,b,c, ⁎ a Nanomalaria Group, Institute for Bioengineering of Catalonia (IBEC), Baldiri Reixac 10-12, ES-08028 Barcelona, Spain b Barcelona Centre for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Rosselló 149-153, ES-08036 Barcelona, Spain c Biomolecular Interactions Team, Nanoscience and Nanotechnology Institute (IN2UB), University of Barcelona, Martí i Franquès 1, ES-08028 Barcelona, Spain d Department of Chemistry, Università degli Studi di Milano, Via Golgi 19, IT-20133 Milano, Italy e Swiss Tropical and Public Health Institute, Socinstrasse 57, PO Box, CH-4002 Basel, Switzerland abstract article info Article history: Received 6 November 2013 Accepted 21 December 2013 Available online 7 January 2014 Keywords: malaria nanomedicine Plasmodium polyamidoamines polymer–drug carriers targeted drug delivery Current malaria therapeutics demands strategies able to selectively deliver drugs to Plasmodium-infected red blood cells (pRBCs) in order to limit the appearance of parasite resistance. Here, the poly(amidoamines) AGMA1 and ISA23 have been explored for the delivery of antimalarial drugs to pRBCs. AGMA1 has antimalarial activity per se as shown by its inhibition of the in vitro growth of Plasmodium falciparum, with an IC 50 of 13.7 μM. Fluorescence- assisted cell sorting data and confocal fluorescence microscopy and transmission electron microscopy images indi- cate that both polymers exhibit preferential binding to and internalization into pRBCs versus RBCs, and subcellular targeting to the parasite itself in widely diverging species such as P. falciparum and Plasmodium yoelii, infecting humans and mice, respectively. AGMA1 and ISA23 polymers with hydrodynamic radii around 7 nm show a high loading capacity for the antimalarial drugs primaquine and chloroquine, with the final conjugate containing from 14.2% to 32.9% (w/w) active principle. Intraperitoneal administration of 0.8 mg/kg chloroquine as either AGMA1 or ISA23 salts cured P. yoelii–infected mice, whereas control animals treated with twice as much free drug did not survive. These polymers combining into a single chemical structure drug carrying capacity, low unspecific tox- icity, high biodegradability and selective internalization into pRBCs, but not in healthy erythrocytes for human and rodent malarias, may be regarded as promising candidates deserving to enter the antimalarial therapeutic arena. © 2014 Elsevier B.V. All rights reserved. 1. Introduction More than 40% of the world's population lives at risk of contracting malaria. The most recent estimates indicate several hundred million clinical cases and 660,000 deaths in 2010 [1,2], of which the large major- ity are children below 5 years old [3,4]. The recent call for elimination and eradication of the disease requires research from multiple fronts, in- cluding developing strategies for the efficient delivery of new medicines [5]. Five Plasmodium species cause disease in humans, namely, P. vivax, P. ovale, P. malariae, P. knowlesi [6] and P. falciparum, with the latter being responsible for the most deadly and severe cases. When taking a blood meal, the female Anopheles mosquito inoculates Plasmodium spo- rozoites that in the liver infect hepatocytes and proliferate into thou- sands of merozoites [7]. Merozoites invade red blood cells (RBCs), where they build a parasitophorous vacuole inside which the parasite develops first into rings, and then into the late forms trophozoites and schizonts. Schizont-infected RBCs burst and release more merozoites, which start the blood cycle again. Because the blood-stage infection is responsible for all symptoms and pathologies of malaria, Plasmodium- infected RBCs (pRBCs) are a main chemotherapeutic target [8]. Since antimalarial drug delivery currently relies on compounds with little or no specificity for pRBCs, the administration of most drugs re- quires high doses. However, the unspecificity of toxic drugs demands low concentrations to minimize undesirable side effects, thus incurring the risk of sublethal doses favoring the appearance of resistant pathogen strains [9]. Nanomedicine, which uses nanosized tools for the treatment of disease [10], can fulfill the objective of achieving the intake of total amounts sufficiently low to be innocuous for the patient, but locally still lethal for the parasite. The development of novel delivery ap- proaches is less expensive than finding new antimalarial drugs and may optimize their rate of release [11]. Current immunoliposomal pro- totypes engineered for the delivery of antimalarial drugs specifically to pRBCs [12,13] rely on antibody targeting and contain special lipids, making their synthesis too expensive for their practical widespread use in the routine treatment of most malaria cases, which are in devel- oping areas with low per capita incomes. An essential aspect for the suc- cessful development of antimalarial nanomedicines resides on the choice of targeting elements, of which it has to be considered their Journal of Controlled Release 177 (2014) 84–95 ⁎ Corresponding author at: Nanomalaria Unit, Centre Esther Koplowitz, 1st floor, CRESIB, Rosselló 149-153, ES-08036 Barcelona, Spain. E-mail address: xfernandez_busquets@ub.edu (X. Fernàndez-Busquets). 0168-3659/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jconrel.2013.12.032 Contents lists available at ScienceDirect Journal of Controlled Release journal homepage: www.elsevier.com/locate/jconrel