In summary, our studies demonstrate that the functionalization
of dendrimers using Diels–Alder reaction, at ambient tempera-
ture, is a suitable strategy to prepare drug conjugates carrying
multiple drug molecules which can be released under physio-
logical (37 1C) or pathological (42 1C) conditions. The release
of an active and powerful anti-inflammatory and antibacterial
agent by rDA could be particularly attractive for therapeutic
interventions against bacterial infections accompanied by an
increased local or systemic body temperature. The fine-tuning
of rDA reactions within the physiologically and pathologically
relevant temperature range makes the synthesis of other drug-
dendrimer conjugates widely applicable, and offers advantages
over free drugs by providing better temporal and spatial drug
concentration at the sites of excessive ROS production and
inflammation.
We would like to thank Natural Sciences and Engineering
Research Council of Canada, (NSERC), Canadian Institutes
Fig. 2 Generation of superoxide and reactive oxygen species (ROS)
by paraquat (PQ) and H2O2. Microglia were treated with G1-LA8
(12.5 mM), ,G1-Fu8 (12.5 mM) or LA in equimolar concentration
(100 mM) for 24 h. (A) Fluorescent micrographs showing superoxide
anion (O2ꢀ) generation following PQ exposure (500 mM, 3 h) using
dihydroethidium (DHE). (B) Spectrofluorometric determination
of ethidium fluorescence intensity (arb. units). Controls (CTL) =
untreated cells (n = 6). (C) Fluorescent micrographs showing ROS
generation following H2O2 exposure (200 mM, 3 h) using DCFH-DA;
Scale bar, 20 mm. (D) Spectrofluorometric determination of DCF
fluorescence intensity (arbitrary units relative to control set at 1).
of Health Research (CIHR) and Fonds de Recherche en Sante
du Quebec (FRSQ) and Centre for Self-Assembled Chemical
Structures (Fonds quebecois de la Recherche sur la Nature et
´
´
´
´
les Technologies) for financial support.
Notes and references
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and without LA in cells exposed to LPS, a well established
endotoxin released from Gram negative bacteria, which is
commonly used to mimic bacterial infection and to activate
microglia. The results (Fig. S3, see ESIw) clearly show that
LPS induced an increase in nitric oxide which was significantly
reduced, with LA, and the dendrimer with or without bound
LA (i.e. G1-Fu8 and G1-LA8). We are intrigued by the activity
of G1-Fu8, and the studies to understand it in more detail are
currently being pursued in our laboratories.
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c
12148 Chem. Commun., 2011, 47, 12146–12148
This journal is The Royal Society of Chemistry 2011