An Optical Sensor Based on a Photonic Polymer Film to Detect Calcium in Serum

Abstract

An optical calcium sensor is fabricated based on a cholesteric liquid crystalline (CLC) polymer containing benzoic acid metal binding sites. A chiral imprinted CLC polymer is made which is subsequently treated with KOH to yield a responsive green reflecting film. On investigation of various metal ions, the polymer film shows a high optical response, and selectivity for calcium ions, which is related to the preorganized binding sites in the ordered liquid crystalline phase, leading to a blue reflecting film. The photonic polymer film is sensitive to Ca2+ within the physiologically relevant concentration range of 10−4 to 10−2 m. Measurement of total calcium concentration in serum is also investigated using the film. The optical responses of normal serum and samples mimicking hypocalcemia and hypercalcemia can be clearly distinguished, providing a cheap, battery‐free, and easy‐to‐use alternative for calcium determination in clinical diagnostics.

Biomaterial microlasers implantable in the cornea, skin, and blood

“…Liquid crystal Bragg onion lasers had a linear temperature dependence in the lasing wavelengths, offering the possibility of temperature sensing, but can be made also temperature insensitive by polymerizing into solid spheres [30,31]. The periodicity of polymerized cholesteric liquid crystals can be made sensitive to a variety of analytes including metal ions [32,33], amino acids [34] and pH [35], for chemical and biomolecular sensing applications. In this work synthetic dyes were employed as gain material, but other biocompatible materials could be used, for example fluorescent proteins [36,37], vitamins [15] and medically approved dyes (fluorescein and indocyanine green).…”

Chromogenic Photonic Crystal Sensors Enabled by Multistimuli‐Responsive Shape Memory Polymers

“…[4][5][6][7][8][9][10] Various photonic crystal geometries ranging from mesoporous 1D Bragg stacks and 2D photonic crystal fibers to 3D inverted photonic crystals and porous silicon membranes, coupled with many stimuliresponsive materials, such as hydrogels (including those with specific analytebinding ligands), oxides, semiconductors, metals, and polymers, have enabled sensitive colorimetric and/or spectroscopic detection of a large variety of chemical and biological analytes (e.g., glucose, proteins, metal ions, alcohols, and water). [4,7,9,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Drastic color shifts of photonic crystal sensors are commonly achieved through changes in lattice constants (for example, induced by swelling/ deswelling of hydrogels) and/or effective refractive indices (e.g., caused by liquid uptake in porous photonic crystals). [6,28,29] Unfortunately, nearly all state-of-the-art photonic crystal sensors need to stay immersed in the analytes (either in gas or liquid phase) during optical readout.…”

“…The visually perceived color changes associated with stimuli‐responsive PBG shifts in active photonic crystals have also been extensively exploited as a more convenient transduction mechanism than traditional electrical pathways for developing novel, low‐cost chemical sensors . Various photonic crystal geometries ranging from mesoporous 1D Bragg stacks and 2D photonic crystal fibers to 3D inverted photonic crystals and porous silicon membranes, coupled with many stimuli‐responsive materials, such as hydrogels (including those with specific analyte‐binding ligands), oxides, semiconductors, metals, and polymers, have enabled sensitive colorimetric and/or spectroscopic detection of a large variety of chemical and biological analytes (e.g., glucose, proteins, metal ions, alcohols, and water) . Drastic color shifts of photonic crystal sensors are commonly achieved through changes in lattice constants (for example, induced by swelling/deswelling of hydrogels) and/or effective refractive indices (e.g., caused by liquid uptake in porous photonic crystals) .…”

Test‐Paper‐Like Photonic Crystal Viscometer

“…Because of the tunable crystal structure and optical signal under external stimuli or in different environment, the responsive PCs are intrinsically suitable for portable and visually detectable sensors. As a matter of fact, previous research works did report many photonic sensors, which utilized the change of structural color and reflection spectrum to measure or detect temperature, mechanical force,[3a,8] pH value, metal ions, solvent, vapor, humidity, drugs, biological molecules, etc . However, it is still a big challenge to extend photonic sensing to the measurements of more physical properties of matters besides the mechanic stress, such as viscosity, electrical conductivity, or refractive index, since most of the reported PC sensors are designed for detection of chemical species.…”