Fiberoptic DNA sensor array capable of detecting point mutations

The first integrated fiberoptic DNA sensor array capable of simultaneously monitoring multiple hybridization events has been prepared. In this study, 5'-amino-terminal DNA probes were covalently immobilized by reaction with succinimidyl ester residues in acrylamide-based polymer matrices. DNA sensor arrays of three different oligonucleotide probes, p(dA)(18-mer), H-ras wild-type (10-mer), and H-ras mutant (11-mer) were fabricated, and real-time hybridization of 5'-fluorescein isothiocyanate (FITC)-labeled target oligonucleotides to the array was monitored. H-ras wild-type and Eta-ras mutant differ by a one-base substitution (point mutation) and were used to demonstrate the sensor's ability to distinguish point mutations. Thermal studies indicated a 13 degrees C decrease in the Tm of a duplex with a single-base mismatch. The fiberoptic DNA sensor array was used to discriminate a point mutation by monitoring the real-time hybridization of FITC-labeled target oligonucleotides at 54 degrees C and detected labeled-target oligonucleotides in the range 0.2-196 nM. The lower detection limit is approximately an order of magnitude lower than previously reported DNA biosensors. The DNA sensor array was used to positively identify a point mutation of a biotin-primer-labeled (109 bp) PCR product of the H-ras oncogene. The unitary fiberoptic sensor array is highly sensitive, has the ability to determine point mutations, and has the potential to sample submicroliter volumes due to the small volumes of the individual array elements (20 pL).

Fast temporal response fiber-optic chemical sensors based on the photodeposition of micrometer-scale polymer arrays

Fiber-optic chemical sensor microarrays for the detection of pH and O2 have been developed with subsecond response times. Sensor microarrays are fabricated by the covalent immobilization (pH sensor arrays) or the physical entrapment (O2 sensor arrays) of fluorescent indicators in photodeposited polymer matrices on optical imaging fibers. Polymer microarrays are comprised of thousands of individual elements photodeposited as hemispheres such that each element of the sensor array is coupled directly to a discrete optical element of the imaging fiber and is not in contact with other neighboring elements. Because of the hemispherical shape and the individuality of the array elements, diffusion of analyte to the sensor elements is dominated by radial diffusion, resulting in a rapid response time. pH-sensitive arrays based on fluorescein respond to a 1.5-unit pH change within 300 ms, while the O2-sensitive arrays respond to O2 changes within 200 ms (90% of steady state response).

Multianalyte biosensors on optical imaging bundles

We present an optical biosensor design that expands the utility of enzyme biosensors. These biosensors are fabricated by site-selective photodeposition of analyte-sensitive polymer matrices on optical imaging fibres. These dual-analyte arrays allow for the simultaneous, independent measurement of the analyte of interest and the transducing analyte. The first integrated optical-biosensors using this design have been prepared that allow both the dependent and independent analytes to be measured simultaneously, for example penicillin and pH (Healey & Walt, 1995) or glucose and O2 (Li & Walt, 1995). Independent measurement of the transducing analyte allows penicillin or glucose to be quantitated in the presence of a concurrent pH or O2 change, respectively. Penicillin can be measured in the range 0.25-10.0 mM in the pH range 6.2-7.5. Glucose can be measured in the range 0.6-20.0 mM in the O2 range 20-100%. The utility of the sensor design was demonstrated by using the penicillin-dual-analyte biosensor to quantitate penicillin produced during a Penicillium chrysogenum fermentation.

Improved fiber-optic chemical sensor for penicillin

An optical penicillin biosensor is described, based on the enzyme penicillinase. The sensor is fabricated by selective photodeposition of analyte-sensitive polymer matrices on optical imaging fibers. The penicillin-sensitive matrices are fabricated by immobilizing the enzyme as micrometer-sized particles in a polymer hydrogel with a covalently bound pH indicator. An array of penicillin-sensitive and pH-sensitive matrices are fabricated on the same fiber. This array allows for the simultaneous, independent measurement of pH and penicillin. Independent measurement of the two analytes allows penicillin to be quantitated in the presence of a concurrent pH change. An analysis was conducted of enzyme kinetic parameters in order to model the penicillin response of the sensor at all pH values. This analysis accounts for the varying activity of the immobilized penicillinase at different pH values. The sensor detects penicillin in the range 0.25-10.0 mM in the pH range 6.2-7.5. The sensor was used to quantify penicillin concentration produced during a Penicillium chrysogenum fermentation.

Photodeposition of micrometer-scale polymer patterns on optical imaging fibers

Microstructures were fabricated on optical imaging fibers with a photopolymerization technique. Monodisperse polymeric microarrays were produced containing spots of 2.5 micrometers in diameter spaced 4.5 micrometers apart. Polymer microarrays were also deposited on other substrates by using imaging fibers for light delivery. The technique allows micrometer-scale photopatterning with masks larger than the desired dimensions.