Improved Preservation of Histomorphology Resulting from Combined Effect of Tris-Hcl Buffered Formalin Fixative and Controlled Fixation Time

Formalin fixation is rife with standardization problems which are possible sources of pre-analytical errors. This study therefore attempts to identify a formalin-based fixative and fixation time that collectively provides the best balance of preservation of tissue morphology using mouse liver as a model. Fifty (50) albino mice aged 6-8 weeks of both sexes were sacrificed by cervical dislocation and their liver were harvested, pooled together and randomly divided into control and experimental groups. Control groups were fixed in 10ml of 10% formalin for 2, 6, 10, 14, 18, 22 and 24 hours at room temperature respectively, while each of the experimental group was fixed separately in 10ml of tris-Hcl buffered 10% formalin at pH 7.2, 7.4, 7.6 and 7.8 respectively for the same duration at room temperature and thereafter processed for general tissue morphology. Nuclear, cytoplasm and cell membrane integrity were assessed as indices of the combined efficacy of fixative and fixation time. Morphology was scored using a four-point grading scale with 1 being poor and 4 being excellent. Tissues fixed with 10% formalin were generally poorly preserved, whereas, tissues fixed with tris-Hcl buffered 10% formalin at pH of 7.2 for 18 and 22 hours and pH 7.4 for 24 hours were excellently preserved. Morphological quality of tissues declined at higher pH values. Combination of tris-Hcl buffered formalin at pH (7.2 / 7.4) for 18, 22 / 24 hours provide an excellent formalin-based fixative and fixation time for adequate tissue preservation for histopathology analysis. Keywords: Buffer, fixative, fixation, morphology, preservation