Turbidimetric (Kinetic) Solubility Assay

Domainex’s turbidimetric (kinetic) solubility assay is a cost-efficient, medium-throughput method to assess the solubility of compounds by measuring the light absorbance of the sample at 620 nm wavelength. This assay is highly customisable, e.g. with regard to compound concentration, buffer, incubation time, etc. It is therefore feasible to replicate biological assay conditions and evaluate the solubility of test compounds under these specific conditions.

Standard Experimental Procedure

Test compounds are prepared in DMSO at a range of concentrations (3-fold serial dilution from 10 mM DMSO stocks). Each sample is then diluted 1 in 50 into Dulbecco's Phosphate-Buffered Saline (DPBS), pH 7.4 (resulting in a final DMSO concentration of 2%), and incubated at 25°C for 1 hour before the absorbance at 620 nm wavelength is measured. The solubility is calculated by determining the concentration when a validated threshold is surpassed (typically 1.5-fold of the absorbance of DMSO-only controls). 

Example solubility data is shown in Figures 1 and 2.

Figure 1: Solubility of Pyrene, Ketoconazole, and Hydrocortisone. Compounds were assessed using Domainex’s Standard Experimental Procedure (incubated in DPBS, pH 7.4 for 1 hour at 25 °C).

Figure 2: Reproducibility of solubility data for Pyrene and Ketoconazole acquired over multiple runs

Deliverables

The results are reported in Excel file format as solubility values (µM). Any relevant comments are also included in the report.

Turnaround time from receipt of the test compounds to release of data is typically ≤2 weeks.