Evaluation of polyesteramide (PEA) and polyester (PLGA) microspheres as intravitreal drug delivery systems in albino rats

Tobias Peters, Seong Woo Kim, Vinicius Castro, Krunoslav Stingl, Torsten Strasser, Sylvia Bolz, Ulrich Schraermeyer, George Mihov, Meng Meng Zong, Vanessa Andres-Guerrero, Rocio Herrero Vanrell, Aylvin A. Dias, Neil R. Cameron, Eberhart Zrenner

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)


Purpose To study the suitability of injectable microspheres based on poly(ester amide) (PEA) or poly lactic-co-glycolic acid (PLGA) as potential vehicles for intravitreal drug delivery in rat eyes. Dexamethasone-loaded PEA microspheres (PEA + DEX) were also evaluated. Methods Forty male Sprague Dawley rats were divided into four groups that received different intravitreally injected microspheres: PEA group (n = 12); PLGA group (n = 12); PEA + DEX group (n = 8); and control group (no injection, n = 8). Electroretinography (ERG), fundus autofluorescence (FAF), and spectral domain optical coherence tomography (sdOCT) were performed at baseline, weeks 1 and 2, and months 1, 2, and 3 after intravitreal injection. Eyes were histologically examined using light microscopy and transmission electron microscopy at the end of the in vivo study. Results There were no statistically significant changes in ERG among the groups. Abnormal FAF pattern and abnormal deposits in OCT were observed after injection but almost completely disappeared between week 2 and month 3 in all injected groups. GFAP staining showed that Müller glia cell activation was most pronounced in PLGA-injected eyes. Increased cell death was not observed by TUNEL staining at month 1. In electron microscopy at month 3, the remnants of microparticles were found in the retinal cells of all injected groups, and loss of plasma membrane was seen in the PLGA group. Conclusions Although morphological changes such as mild glial activation and material remnants were observed histologically 1 month and 3 months after injection in all injected groups, minor cell damage was noted only in the PLGA group at 3 months after injection. No evidence of functional abnormality relative to untreated eyes could be detected by ERG 3 months after injection in all groups. Changes observed in in vivo imaging such as OCT and FAF disappeared after 3 months in almost all cases.

Original languageEnglish
Pages (from-to)157-168
Number of pages12
Publication statusPublished - 2017 Apr 1
Externally publishedYes


  • Aliphatic dicarboxylic acids and aliphatic α-ω diols (PEA)
  • Fundus auto-fluorescence
  • Immunohistochemistry
  • Invivo electroretinography
  • Invivo optical coherence tomography
  • Poly ester amide based on α-amino acids
  • Poly lactic-co-glycolic acid (PLGA)
  • TUNEL stain
  • Transmission electron microscopy

ASJC Scopus subject areas

  • Biophysics
  • Bioengineering
  • Ceramics and Composites
  • Biomaterials
  • Mechanics of Materials


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