FTIR was used to examine the change in the secondary structure of the PLGA 75:25 microspheres at 278 K. For FTIR analysis, each microsphere material (300 µg) was mixed with 100 mg potassium bromide (KBr) using an agate mortar and pressed into 7 mm selfsupporting disks using a load of 10 Tons. FTIR spectra were acquired using a Cary 680 FTIR spectrometer (Agilent Technologies, CA, USA) with 60 scans and a resolution of 1 cm -1 . At least four spectra were measured for each material. The recorded spectra were normalised based on the total area under the curve.