Effects of glycerol processing on the biomechanical, structural, optical, and antimicrobial properties of human amniotic membrane

Human amniotic membrane (hAM) is used as a biological dressing in burn care, and preservation methods may influence its structural and functional characteristics. This study evaluated the effects of a glycerol-based processing and preservation method on properties of hAM. Placentas were obtained from 142 consenting donors following elective caesarean section at a tertiary academic hospital. hAM was processed using ≥99.5% glycerol with agitation cycles and intermediate saline rinses following antibiotic-antifungal decontamination. Paired processed and unprocessed samples from 71 donors were assessed for biomechanical properties, optical transmittance, thickness, bacterial inhibition, and histological characteristics. Statistical analyses included paired t-tests, repeated-measures ANOVA, and effect sizes (Cohen's d). Processing resulted in modest reductions in ultimate tensile strength (- 7.6%) and tensile stress (- 6.1%), with small effect sizes, while tensile strain was not significantly altered. Optical transmittance increased from 90.8 to 97.1% (p < 0.001; Cohen's d -0.92), while thickness decreased by 2.9%. Following 12 months of refrigerated storage, glycerol-processed hAM produced larger inhibition zones than unprocessed hAM against all five tested bacterial species under the same conditions. Qualitative histological assessment demonstrated epithelial loss, reduced stromal cellularity, and altered stromal morphology, while the basement membrane remained visibly continuous. Processed hAM demonstrated measurable biomechanical properties and bacterial inhibition, together with increased optical transmittance, and processing-associated histological changes. These in vitro findings characterize the effects of the glycerol-based processing and preservation method but do not establish clinical efficacy. Further in vivo evaluation is required to determine whether these laboratory findings translate into safe and effective clinical performance.