Slide cover glass immobilized liquid crystal microdroplets for sensitive detection of an IgG antigen

Rabbit IgG antigen sensing liquid crystal (LC) microdroplets with a size variation from 15-20 mm were prepared using 98% nematic 4-cyano-4'-pentyl biphenyl (5CB), poly(styrene-b-acrylic acid) copolymer (PS-b-PA), and sodium dodecyl sulfate (SDS) as an interfacial modifier. The slide cover glass immobilized AIgG conjugated LC microdroplets were found to be sensitive in showing optical signals on interactions with an IgG antigen both in phosphate-buffered saline solution (PBS) and in the presence of other media i.e., 10 wt% fetal bovine serum (FBS) and blood plasma. The slide cover glass has enhanced the possibilities of efficient interactions of the IgG antigen with immobilized AIgG conjugated LC microdroplets and decreased the lower limit of detection for the IgG antigen down to 25 ng mL(-1) within a contact time of 30 min in PBS solution at room temperature. The sensitivity of cover-glass-immobilized LC microdroplets in detection of IgG in solution with 10 wt% amount of FBS and blood plasma is found to be same (25 ng mL(-1) of IgG) as found in PBS solution on comparing the response of slide cover glass immobilized LC microdroplets for IgG at similar to 50% orientation transitions in LC microdroplets. However, the response time of slide-cover-glass-immobilized LC microdroplets for detection of IgG in solution with 10 wt% FBS or blood plasma is delayed to 60 minutes. The slide-cover-glass- immobilized LC microdroplets have also shown excellent storage stability and reuse applicability in sensitive detection of IgG in biological simulated fluids.