[1] Univ Cambridge, Dept Chem, Melville Lab Polymer Synth, Cambridge CB2 1EW, England
[2] Univ Cambridge, Cambridge Ctr Brain Repair, Dept Clin Neurosci, Cambridge CB2 0PY, England
[3] NCI, Radiat Oncol Branch, NIH, Bethesda, MD 20892 USA
[4] Univ Cambridge, Addenbrookes Hosp, Dept Clin Neurosci, Div Neurosurg, Hills Rd, Cambridge CB2 0QQ, England
[5] Univ Birmingham, Brain Canc Program, Coll Med & Dent Sci, Inst Canc & Genom Sci, Birmingham B15 2TT, W Midlands, England