Bioassays using plasmonic scattering from noble metal nanostructures

A biosensing method for measuring concentration of an analyte that induces colloidal aggregation, the method comprising:

• (a) preparing colloids comprising a noble metal and at least partially coated with a binding component having an affinity for the analyte, and wherein the colloids are sized to scatter light according to the Rayleigh theory;
• (b) exposing the colloids with electromagnetic radiation at a frequency that is absorbed and scattered;
• (c) measuring the intensity of scattered light from colloids, wherein the intensity of the scattered light is measured at two angles relative to the incident light;
• (d) contacting the colloids with an analyte that has an affinity for the binding component;
• measuring the intensity of scattered light from the colloids, wherein the intensity of the scattered light is measured at the same two angles as in step (c);
• and
• (e) determining a ratio between the measured intensity values at the two angles, wherein the ratio approaches unity as aggregation increases.

A bioassay method for measuring concentration of receptor-ligand binding, the method comprising:

• (a) preparing metallic nanostructures immobilized on a surface wherein the metallic nanostructures have positioned thereon a receptor molecule having affinity for the ligand;
• (b) contacting the metallic nanostructures attached to the receptor molecule with a sample suspected of comprising the ligand of interest, wherein any ligand in the sample will bind to the receptor molecule to form a receptor-ligand complex;
• (c) contacting the receptor-ligand complex with a detector molecule having affinity for the ligand to form a receptor-ligand-detector complex, wherein the detector molecule is attached to a metallic nanostructure, wherein binding of the ligand to the receptor forms a metal complex comprising metallic nanostructures on opposing ends of receptor-ligand-detector molecule complex;
• (d) exposing the metal complex to electromagnetic radiation at a frequency that is absorbed and/or scattered by the metallic nanostructures;
• and
• (e) measuring an effect of coupling of long range plasmon scatter from the metallic nanostructures of the opposing ends of the metal complex, wherein the effect includes spectral shifts of wavelength absorption due to long range plasmon coupling from the two opposing metallic nanostructures, measuring the ratio of scattered intensities from coupling of the long-range plasmon scatter at two unique wavelength or measuring the reduction in polarization of the coupling of the long range plasmon scatter when the metallic nanostructure move to close proximity.

A biosensing method for measuring concentration of an analyte, the method comprising:

• (a) preparing metallic nanostructures immobilized on a surface wherein the metallic nanostructures are attached to a capture molecule having affinity for the analyte, and wherein the metallic nanostructures are sized to scatter light according to the Rayleigh theory;
• (b) exposing the metallic nanostructures and capture molecule with electromagnetic radiation at a frequency that is absorbed and scattered by the metallic nanostructures;
• (c) measuring the intensity of scattered light, wherein the intensity of the scattered light is measured at two angles relative to the incident light;
• (d) contacting the capture molecule with a sample suspected of comprising the analyte of interest, wherein any analyte in the sample will bind to the capture molecule to form a capture-analyte complex;
• (e) contacting the capture-analyte complex with a detector molecule having affinity for the analyte to form a capture-analyte-detector complex, wherein the detector molecule is attached to a metallic nanostructure to form a metal complex comprising metallic nanostructures on opposing ends of capture-analyte-detector molecule complex;
• (f) measuring the intensity of scattered light from formed metal complexes, wherein the intensity of the scattered light is measured at the same two angles as in step (c);
• and
• (g) determining a ratio between the measured intensity values at the two angles, wherein the ratio approaches unity as aggregation increases.

A biosensing method for measuring concentration of an analyte, the method comprising:

• (a) preparing metallic nanostructures immobilized on a surface wherein the metallic nanostructures have positioned thereon a receptor molecule having affinity for the ligand;
• (b) exposing the metallic nanostructures and receptor molecule with electromagnetic radiation at a frequency that is absorbed and scattered by the metallic nanostructures;
• (c) measuring the absorption intensity and wavelength of scattered light;
• (d) contacting the metallic nanostructures attached to the receptor molecule with a sample suspected of comprising the ligand of interest, wherein any ligand in the sample will bind to the receptor molecule to form a receptor-ligand complex;
• (e) contacting the receptor-ligand complex with a detector molecule having affinity for the ligand to form a receptor-ligand-detector complex, wherein the detector molecule is attached to a metallic nanostructure to form a metal complex comprising metallic nanostructures on opposing ends of receptor-ligand-detector molecule complex;
• (f) measuring the absorption intensity and wavelength of scattered light from formed metal complexes;
• and
• (g) determining the spectral shift in absorption wavelength, which is shifted as aggregation increases.