Minocycline-loaded nHAP/PLGA microspheres for prevention of injury-related corneal angiogenesis

Corneal neovascularization (CoNV) threatens vision by disrupting corneal avascularity, however, current treatments, including pharmacotherapy and surgery, are hindered by limitations in efficacy and adverse effects. Minocycline, known for its anti-inflammatory properties, could suppress CoNV but faces challenges in effective delivery due to the cornea's unique structure. Therefore, in this study a novel drug delivery system using minocycline-loaded nano-hydroxyapatite/poly (lactic-co-glycolic acid) (nHAP/PLGA) nanoparticles was developed to improve treatment outcomes for CoNV.

Ultra-small nHAP was synthesized using high gravity technology, then encapsulated in PLGA by a double emulsion method to form nHAP/PLGA microspheres, attenuating the acidic by-products of PLGA degradation. The MINO@PLGA nanocomplex, featuring sustained release and permeation properties, demonstrated an efficient delivery system for minocycline that significantly inhibited the CoNV area in an alkali-burn model without exhibiting apparent cytotoxicity. On day 14, the in vivo microscope examination and ex vivo CD31 staining corroborated the inhibition of neovascularization, with the significantly smaller CoNV area (29.40% ± 6.55%) in the MINO@PLGA Tid group (three times daily) than that of the control group (86.81% ± 15.71%), the MINO group (72.42% ± 30.15%), and the PLGA group (86.87% ± 14.94%) (p < 0.05). Fluorescein sodium staining show MINO@PLGA treatments, administered once daily (Qd) and three times daily (Tid) demonstrated rapid corneal epithelial healing while the Alkali injury group and the DEX group showed longer healing times (p < 0.05). Additionally, compared to the control group, treatments with dexamethasone, MINO, and MINO@PLGA were associated with an increased expression of TGF-β as evidenced by immunofluorescence, while the levels of pro-inflammatory cytokines IL-1β and TNF-α demonstrated a significant decrease following alkali burn. Safety evaluations, including assessments of renal and hepatic biomarkers, along with H&E staining of major organs, revealed no significant cytotoxicity of the MINO@PLGA nanocomplex in vivo.

The novel MINO@PLGA nanocomplex, comprising minocycline-loaded nHAP/PLGA microspheres, has shown a substantial capacity for preventing CoNV. This study confirms the complex's ability to downregulate inflammatory pathways, significantly reducing CoNV with minimal cytotoxicity and high biosafety in vivo. Given these findings, MINO@PLGA stands as a highly promising candidate for ocular conditions characterized by CoNV.