HEPES

Interaction of HEPES buffer with glass-ceramic scaffold: Can HEPES replace TRIS in SBF?[Pubmed:27889932]

J Biomed Mater Res B Appl Biomater. 2018 Jan;106(1):143-152.

An international standard (ISO: 23317:2014) exists for the in vitro testing of inorganic biomaterials in simulated body fluid (SBF). This standard uses TRIS buffer to maintain neutral pH in SBF, but in our previous paper, we showed that the interaction of a tested glass-ceramic material with TRIS can produce false-positive results. In this study, we evaluated whether the HEPES buffer, which also belongs to the group of Good s buffers, would be more suitable for SBF. We compared its suitability in two media: SBF with HEPES and demineralized water with HEPES. The tested scaffold (45S5 bioactive glass-based) was exposed to the media under a static-dynamic arrangement (solutions were replaced on a daily basis) for 15 days. Leachate samples were collected daily for the analysis of Ca(2+) ions and Si (AAS), (PO4 )(3-) ions (UV-VIS), and to measure pH. The glass-ceramic scaffold was analyzed by SEM/EDS, XRD, and WD-XRF before and after 0.3, 1, 3, 7, 11, and 15 days of exposure. Our results confirmed the rapid selective dissolution of the glass-ceramic crystalline phase (Combeite) containing Ca(2+) ions due to the presence of HEPES, hydroxyapatite supersaturation being reached within 24 h in both solutions. These new results suggest that, like TRIS, HEPES buffer is not suitable for the in vitro testing of highly reactive inorganic biomaterials (glass, glass-ceramics). The ISO standard for such tests requires revision, but HEPES is not a viable alternative to TRIS buffer. (c) 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 143-152, 2018.

Hydrophilic interaction liquid chromatography method development and validation for the assay of HEPES zwitterionic buffer.[Pubmed:27993432]

J Pharm Biomed Anal. 2017 Feb 20;135:227-233.

HEPES is a zwitterionic buffer component used as a raw material in the GMP-manufacturing of advanced therapy medicinal products (ATMPs), hence requiring an adequate assay method with sufficient selectivity toward related impurities. Therefore, a hydrophilic interaction chromatography (HILIC) method was developed. Different factors were investigated towards the retention behavior of HEPES, its analogue EPPS and its starting material isethionate: pH, ion concentration and organic solvent ratio of the mobile phase, as well as column temperature. Moreover, stress testing resulted in the N-oxide degradant, identified by high resolution MS. The final method consisted of an isocratic system with an aqueous (pH 2.0 with H3PO4) acetonitrile (35:65, v/v) mobile phase on a zwitterionic HILIC (Obelisc N) column with a flow rate of 0.5mL/min and UV detection at 195nm. The assay method of HEPES was validated, obtaining adequate linearity (R(2)=0.999), precision (RSD of 0.5%) and accuracy (recovery of 100.08%). Finally, the applicability of the validated method was demonstrated by analysis of samples from different suppliers.

Influence of different buffers (HEPES/MOPS) on keratinocyte cell viability and microbial growth.[Pubmed:27060444]

J Microbiol Methods. 2016 Jun;125:40-2.

This study assessed the effect of the buffers 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) and 3-(N-morpholino) propanesulfonic acid (MOPS) on keratinocyte cell viability and microbial growth. It was observed that RPMI buffered with HEPES, supplemented with l-glutamine and sodium bicarbonate, can be used as a more suitable medium to promote co-culture.