Photonic biosnesor arrays

A biosensor array for Plasmon resonance-based sensing of a plurality of different biological targets simultaneously, the array comprising a transparent substrate having a surface bearing a plurality of assay spots for Plasmon resonance sensing, each of said assay spots comprising a discrete metallic island, a said metallic island comprising a plurality of metallic nanoparticles to which are attached functionalising molecules for binding to a said biological target, different said islands being different said functionalising molecules for binding to different ones of said biological targets, and wherein total internal reflection of light at said surface at a wavelength at or near a said plasmon resonance results in scattering of said light away from said surface, said scattering being modulated by said binding of said biological targets.

A biosensor array as claimed in claim 1, wherein said metallic nanoparticles have at least one dimenstion of less than 30 nm, and comprise rod-like nanoparticles.

A biosensor array as claimed in claim 1, wherein said nanoparticles include nanoparticles forming an optical antenna for said light, wherein a said optical antenna comprises an adjacent pair of nanoparticles having a generally rod-like or triangular shape, and having adjacent ends separated by a gap of less than 100 nm, preferably less than 50 nm, said nanoparticles having physical lengths which are resonant for a said plasmon resonance at substantially the same optical wavelength.

A biosensor array as claimed in claim 1, further comprising at least one control spot substantially lacking said functionalising molecules, and wherein said control spot comprises an array of metallic elements configured to produce an interference or fringe pattern when said control spot is viewed.

A biosensor array as claimed in claim 1, wherein said transparent substrate is configured as a Dove prism, and includes an edge or grating optical coupling for coupling said light into an edge of said transparent substrate of said array to waveguide said light within a thickness of said substrate.

A biosensor array as claimed in claim 1, wherein said metallic nanoparticles comprise gold nanoparticles, and wherein said different functionalising molecules are attached to said metallic nanoparticles using the same ligand.

A method as claimed in claim 7, wherein said imaging of said scattered light comprises imaging said array from a side opposite to a side of said array being said assay spots.

A method as claimed in claim 7, wherein said imaging is performed in real-time to follow binding kinetics of said biological targets carried by said fluid, and wherein said analysing comprises determining time variations of binding of said different targets to said different functionalising molecules;

• and further comprising matching said time variations to one or more pathological conditions associated with said biological targets carried by said fluid.

A method as claimed in claim 7, wherein said light comprises light of at least two different wavelengths one to either side of said plasmon resonance, and wherein said analysing includes forming a ratio of signals at said two different wavelengths in said image data.

A method as claimed in claim 7, wherein said analysing comprises comparing a signal from one of said assay spots with a signal from another of said assay spots to compensate for non-specific binding interactions.

A method as claimed in claim 7, wherein said analysing comprises controlling for a bulk refractive index of said fluid using a control spot substantially lacking said functionalising molecules, wherein said control spot is configured to form a diffraction or interference pattern in said imaged scattered light.

A method as claimed in claim 7, wherein said biosensor array has an open top onto which said fluid may be deposited, and one or more built-in semiconductor light sources configured to provide waveguided light within said transparent substrate of said array to excite said plasmons.

A method as claimed in claim 7, wherein said imaging comprises imaging dark-field scattered light through a back surface of said biosensor array.

An apparatus as claimed in claim 17, configured to determine said levels of said different biological targets attached to said array using light of two orthogonal polarisations.

A biosensor array for plasmon resonance-based sensing, the array having a surface bearing a plurality of assay spots, each of said assay spots comprising a conducting material for plasmon resonance sensing, and wherein the array further comprises at least one control spot, said control spot bearing a pattern of conductive elements such that light emitted by plasmon resonance in said control spot exhibits a pattern of interference or fringes.