In Vitro Dual Detection of GNPs Conjugated Rabbit IgG Using Anti-IgG Anchored Calcein Green Fluorescent LC Microdroplets

The 4-cyano-
$4^{\prime }$
-pentyl biphenyl (5CB) liquid crystals molecules are fascinating materials for the fabrication of sensors as they are able to show a detectable optical signal in presence of small variation in surface forces. The sensitivity of 5CB molecules increased further on using them as microdroplets emulsion as compared to layered structures on plannar solid surfaces. The anchoring of receptor (AIgG) on LC microdroplets makes microdroplets capable to produce species specific optical signal in presence of nonspecific interactions. Gold nanoparticles (GNPs) have increased the interactions of antigen (IgG) with LC microdroplets anchored AIgG. The concomitant emission of calcein green fluorescence on interactions of GNPs anchored esterase with LC microdroplet anchored calcein-AM has provided an evidence to confirm the interactions induced transition from radial to bipolar in LC microdroplets. The AIgG (
$4.2~\mu \text{g}$
, 28 pmol) and calcein-AM (
$4.8~\mu \text{g}$
, 4.55 nmol) anchored LC microdroplets within a size variation of 20-
$30~\mu \text{m}$
have shown a lower limit of detection of 0.22 ± 0.001 pmol of IgG in PBS (pH 7.4) within a contact time of 20 minutes. Thus, liquid crystals microdroplets have sufficient scope to develop biosensors for
in vitro
detection of disease causing antigens in biological fluids.