Raman Imaging of PLGA Microsphere Degradation Inside Macrophages

Abstract

Understanding the degradation behavior of polymeric microspheres is crucial for the successful application of such devices in controlled drug delivery. The degradation mechanism of poly(lactic-co-glycolic acid) (PLGA) microspheres inside phagocytic cells is not known, but different models for degradation in aqueous solution have been proposed. We have used confocal Raman spectroscopy and imaging to study the intracellular degradation of PLGA microspheres inside individual macrophages. Our results show that ingested microspheres degrade in a heterogeneous manner, with a more rapid degradation in the center. Comparison of Raman spectra from degrading beads with those of uningested beads reveals that ester hydrolysis occurs throughout the phagocytosed microspheres, with a selective loss of glycolic acid units. Furthermore, we show that PLGA degradation is a cell-mediated process, possibly caused by the low pH of the phagosome and/or the presence of hydrolytic enzymes. In conclusion, we have demonstrated that the chemical composition of degrading polymers inside cells can be probed by Raman spectral imaging. This technique will expand the capabilities of investigating biomaterial degradation in vivo.

Raman microspectroscopy for non-invasive biochemical analysis of single cells

“…The rapidity and high spatial resolution of DRI [19] make it a useful technique for imaging living cells in culture, as demonstrated by the imaging of β-carotene levels in live corpus luteum cells [20], and the subcellular distribution of an anticancer drug in living breast cancer cells [18]. DRI has also been used to probe cell-biomaterial interactions, namely polymer microsphere degradation within fixed macrophages [21]. A limitation of DRI is that only a narrow band of scattering is detected; therefore chemical resolution is restricted, and only a single component can be imaged at any one time.…”

PLGA‐PNIPAM Microspheres Loaded with the Gastrointestinal Nutrient NaB Ameliorate Cardiac Dysfunction by Activating Sirt3 in Acute Myocardial Infarction

“…These results show that PLGA‐PNIPAM microspheres could act as the sustained release carrier of NaB, and the release time could extend to 10 d, which would ensure that NaB could be persistently released for a long time, contributing to a persistent NaB presence and avoiding multiple injections. The size of the PP‐N microspheres was (2.01 ± 0.12) μm, and the cell diameter was nearly 10–20 μm, which ensures that the microspheres could be absorb by cardiomyocyte and endothelial cells through endocytosis 19, 20, 21. Moreover, because the PP‐N microspheres are a thermosensitive hydrogel with a phase‐transition temperature of 30 °C and the animal's temperature is higher than 30 °C, the thermosensitive properties of PP‐N microspheres contribute to persistent NaB existence.…”

Label-free Raman microspectral analysis for comparison of cellular uptake and distribution between nontargeted and EGFR-targeted biodegradable polymeric nanoparticles

“…Ceramide is an intermediate molecule in the synthesis and degradation of sphingomyelin, gangliosides and other glycolipids in cells. 33,34 Therefore, ceramide may be metabolized and degrade inside cells, 35 which may explain the decrease in ceramide amount in cells over time. Higher drug concentration and AUC achieved in cells with nanoparticles compared to free drug may be due to the protection of the nanoparticles of D-ceramide against degradation in cells.…”