Colorimetric Estimation of Protein Content in Gelatin Microparticles

This application note demonstrates a colorimetric method to quantify protein content inside micrometer sized gelatin hydrogel particles. Here, an HRP-coupled antibody (2nd Ab) is used as a probe which activates a visual signal on coming in contact with a Serum antibody (1st Ab) – a blue color is emitted. The 1st Ab is embedded inside the hydrogel matrix of the microparticle. The objective is to quantify surface exposed antibodies (1st Ab) via a color reaction using 3,3'-Diaminobenzidine (DAB).

Two different concentrations of 1st Ab are seeded in Gelatin microparticles, which then are expected to generate different intensities of blue color. The intensity of the blue color is indicative of the quantity of protein at the surface of the particle, which in turn is dependent on the quantity contained within the core of the particle.

If a reaction is positive and if signal differences are detectable, then the method can be used to evaluate protein content in droplets. The protein itself may either originate from direct encapsulation in droplets, or be an outcome of cell activity from encapsulated cells. The tests were done at room temperature as well as at lowered temperature (-20°C) to assess any differences brought about by temperature.