CHEMISTRY, PHYSIOLOGY NEUROSCIENCE, COMPUTER SCIENCES Correction for ‘‘Glyconanoparticles allow pre-symptomatic in Correction for ‘‘The minimum information principle and its vivo imaging of brain disease,’’ by Sander I. van Kasteren, Sandra application to neural code analysis,’’ by Amir Globerson, Eran J. Campbell, Se´bastienSerres, Daniel C. Anthony, Nicola R. Stark, Eilon Vaadia, and Naftali Tishby, which appeared in issue Sibson, and Benjamin G. Davis, which appeared in issue 1, 9, March 3, 2009, of Proc Natl Acad Sci USA (106:3490–3495; January 6, 2009, of Proc Natl Acad Sci USA (106:18–23; first first published February 13, 2009; 10.1073͞pnas.0806782106). published December 23, 2008; 10.1073͞pnas.0806787106). The authors note that due to a printer’s error, an incorrect The authors note that due to a printer’s error, the affiliation version of this article was posted online. The online version has information for Se´bastienSerres and Nicola R. Sibson appeared been replaced. The print version is correct. incorrectly. The correct affiliation is ‘‘CR-UK/MRC Gray Insti- tute for Radiation Oncology and Biology.’’ The corrected affil- www.pnas.org͞cgi͞doi͞10.1073͞pnas.0901850106 iation line appears below. aDepartment of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, United Kingdom; bDepartment of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, United Kingdom; and cCR-UK/MRC Gray Institute for Radiation Oncology and Biology, Radiobiology Research Institute, University of Oxford, Churchill Hospital, Oxford, OX3 7LJ, United Kingdom www.pnas.org͞cgi͞doi͞10.1073͞pnas.0900259106 CORRECTIONS PNAS ͉ March 10, 2009 ͉ vol. 106 ͉ no. 10 ͉ 4061 Downloaded by guest on October 2, 2021 Glyconanoparticles allow pre-symptomatic in vivo imaging of brain disease Sander I. van Kasterena, Sandra J. Campbellb,Se´ bastien Serresc, Daniel C. Anthonyb,1, Nicola R. Sibsonc,1, and Benjamin G. Davisa,1 aDepartment of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, United Kingdom; bDepartment of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, United Kingdom; and cCancer Research United Kingdom, Medical Research Council, and Gray Institute for Radiation Oncology and Biology, Radiobiology Research Institute, University of Oxford, Churchill Hospital, Oxford, OX3 7LJ, United Kingdom Edited by Robert Langer, Massachusetts Institute of Technology, Cambridge, MA, and approved November 20, 2008 (received for review July 14, 2008) Initial recruitment of leukocytes in inflammation associated with rely on water exchange in their inner coordination sphere (26–30). diseases such as multiple sclerosis (MS), ischemic stroke, and HIV- They bring with them disadvantages of low sensitivity and low related dementia, takes place across intact, but activated brain en- avidity for carbohydrate-binding protein targets since they display dothelium. It is therefore undetectable to symptom-based diagnoses low carbohydrate copy numbers(31). Consequently, such agents do and cannot be observed by conventional imaging techniques, which not fully exploit the cluster glycoside effects prevalent in carbohy- rely on increased permeability of the blood–brain barrier (BBB) in drate-protein interaction (31–34), which is known to powerfully later stages of disease. Specific visualization of the early-activated enhance often weak single carbohydrate ligand interactions. Here, cerebral endothelium would provide a powerful tool for the presymp- we describe the design and creation of a T2-type glyconanoparticle tomatic diagnosis of brain disease and evaluation of new therapies. reagent GNP-sLex that was specifically targeted to CD62 (E- and Here, we present the design, construction and in vivo application of P-selectin) by virtue of its decoration with many (millions) of copies carbohydrate-functionalized nanoparticles that allow direct detec- of the relevant, complex, cognate, glycan ligand sialyl LewisX (sLex) tion of endothelial markers E-/P-selectin (CD62E/CD62P) in acute normally found on most bloodborne leukocyte subpopulations. inflammation. These first examples of MRI-visible glyconanoparticles GNP-sLex was selected from a number of glyconanoparticles of display multiple copies of the natural complex glycan ligand of increasing carbohydrate complexity constructed on a platform of selectins. Their resulting sensitivity and binding selectivity has al- cross-linked amine-functionalized iron oxide (35, 36). These nano- lowed acute detection of disease in mammals with beneficial impli- particles circumvent problems of low contrast; their high iron cations for treatment of an expanding patient population suffering content conveys upon them far superior relaxation (and hence from neurological disease. detection) effects compared with T1-agents (37–39). carbohydrates ͉ MRI ͉ multiple sclerosis ͉ selectins Results and Discussion The following features of the construction of the nanoparticles, agnetic resonance imaging (MRI) is now the most widely- including GNP-sLex, were key (Fig. 1): used imaging method for the study of neurologic human M 1. Ready access to a high-Fe-content nanoparticular platform. An disease. Antibody-mediated detection of broad-spectrum inflam- alkali suspension of iron oxide-dextran colloidal was treated mation biomarkers, such as VCAM-1 (1, 2), is not applicable to sequentially with epichlorohydrin and ammonia (37, 40). The brain disease where alternative brain-specific markers exist (3, 4). resulting cross-linked, amine-functionalized dextran-coated par- In addition, previous attempts to detect inflammation (5–8) or to ticle, amine nanoparticle (NH -NP), provided a versatile and target selectin up-regulation with antibodies and small molecules in 2 safe platform for the incorporation of multiple copies of target- vivo have failed (8) or were shown only limited contrast enhance- ments at best (5–7), and none have been applied to validated models ing glycans. of brain disease, such as the MS model MOG-EAE (9–11) or the 2. Multivalent nanoparticular display. Chemical assay through ET-induced focal stroke model (12–14). The carbohydrate-binding ‘‘Fmoc-numbering’’ (41) revealed high levels of amine groups per particle in NH2-NP that in turn allowed the display of large transmembrane proteins CD62E (E-selectin) and CD62P (P- 5 7 selectin) are up-regulated as part of the host response to injury numbers (10 to 10 ) of sugars per particle to fully exploit the or disease where they play a key role in the initial tether-roll phase clustering of selectin receptors on inflamed endothelia. of the homing of leukocytes to sites of inflammation; the brain 3. The development of a ‘‘masked’’ chemical linker group, specif- also utilizes the CD62 proteins (15), and they consequently offer ically SCM (Fig. 1), that could be carried throughout the an ideal, to date underexploited, biomarker for brain disease carbohydrate-assembly synthesis: Attachment of glycans to diagnosis (4). NH2-NP required an amine-reactive linker group. However, the Our strategy for detecting the CD62 proteins exploited their manipulation of a linker precursor to generate an active linker affinity for their cognate ligand molecule type, carbohydrates. This after synthesis of a complex glycan often results in low efficien- approach therefore necessitated precise, chemically-synthesized carbohydrate ligands to mediate CD62 binding and detection. Author contributions: S.I.v.K., D.C.A., N.R.S., and B.G.D. designed research; S.I.v.K., S.J.C., Nano-sized particles(16–20) have been functionalized with carbo- and S.S. performed research; S.I.v.K., S.J.C., S.S., D.C.A., N.R.S., and B.G.D. analyzed data; hydrates for the elegant in vitro study of carbohydrate-mediated and S.I.v.K., D.C.A., N.R.S., and B.G.D. wrote the paper. interactions, such as those mediating marine sponge interac- The authors declare no conflict of interest. tions(17). The platforms for these particles have focused on nano- This article is a PNAS Direct Submission. sized gold (17–19) and cadmium sulfide (CdS) (19–21). Although Freely available online through the PNAS open access option. these are often highly convenient and flexible, they also have 1To whom correspondence may be addressed. E-mail: [email protected], disadvantages, such as the toxicity (22) of CdS-based fluorescent [email protected], or [email protected]. quantum dots and the ligand-lability of gold clusters (23, 24), which This article contains supporting information online at www.pnas.org/cgi/content/full/ is exacerbated in biological media (25). The use of glycosylated 0806787106/DCSupplemental. contrast agents, until now, has been limited to T1-type reagents that © 2008 by The National Academy of Sciences of the USA 18–23 ͉ PNAS ͉ January 6, 2009 ͉ vol. 106 ͉ no. 1 www.pnas.org͞cgi͞doi͞10.1073͞pnas.0806787106 PHYSIOLOGY CHEMISTRY Fig. 1. Design and construction of MRI-active GlycoNanoParticles for in vivo inflammation detection. Use of a masked SCM group in a combined chemo-enzymatic synthetic strategy allowed ready access to the required complex oligosaccharide reagents and the corresponding GNPs modified with mono (GNP-GlcNAc), di- (GNP-LacNAc), tri- (GNP-siaLacNAc), and tetra-saccharides (GNP-sLex). cies and reduced modification yields. We discovered that the assemble complex glycan reagents 2–5 in good yields and with S-cyanomethyl (SCM) (SOCH2OCN) functional group could minimal recourse to protecting group chemistry (see SI).