Nanoscale lipid methylprednisolone conjugates: Synthesis, characterization, and therapeutic efficacy in retinal pigment epithelial cells inflammation

Nanocarrier-mediated delivery of glucocorticoids (GCs) represents a promising therapeutic strategy; yet, the high crystallinity and low aqueous solubility of GCs typically result in low drug loading/encapsulation efficiency and limited shelf stability. This study evaluates new nanoscale lipid-methylprednisolone conjugates (NLMCs) for their ability to address the aforementioned issues while preserving the sustained therapeutic effects of the drug, methylprednisolone. Two novel conjugates, LMC 1 and LMC 2, were synthesized by linking methylprednisolone to stearyl hemisuccinate and stearyl hemiglutarate and their structures were elucidated by spectroscopic techniques. Nanoformulations of LMCs 1-2 were prepared via emulsion evaporation method. The designed NLMCs 1-2 demonstrated desirable critical quality attributes in terms of their size (d_H 100–140 nm), PdI (≤0.2), and zeta potential (−20 to −34 mV). The spherical-type morphology of NLMCs 1-2 was confirmed by AFM, SEM, and TEM. NLMCs 1-2 showed higher entrapment efficiency (≥90%) and exhibited a prolonged drug release profile, with 65-70% of the drug released over 48 h in murine plasma. XTT assay using RPE cell lines confirmed NLMCs 1-2 as nontoxic up to 50 μM. Cellular uptake studies revealed internalization of the NLMCs 1-2 within RPE cell. In-vitro efficacy of NLMCs 1,2 was assessed in RPE cell lines stimulated with peptidoglycan (PGN) induced inflammation. Gene expression analysis using qPCR indicated that NLMCs 1-2 significantly suppressed the expression of pro inflammatory genes ( TNF-α/IL-6/IL-8/IL-17A/IL-17F ) and pain markers ( CxCl2/PDYN ) while simultaneously upregulating anti-inflammatory genes ( IL-10/IL-4 ). ELISA analysis showed that NLMCs 1–2 significantly decreased pro-inflammatory IL-6 levels while increasing anti-inflammatory IL-10 levels. NLMCs 1-2 effectively deliver methylprednisolone to RPE cells, enhancing therapeutic efficacy due to their nanoscale design. Further detailed investigation is required to fully validate the biological performance of NLMCs 1-2.