Novel O2-sensing materials based on spin-coated n-octyltriethoxysilane (Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel films have been synthesized and investigated. These sensors are based on the O2 quenching of tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) ([Ru(dpp)3]2+) sequestered within the xerogels. Scanning electron microscopy and luminescence measurements (steady state and time resolved) have been used to investigate the structure of these films and their analytical figures of merit and determine the underlying reasons for their observed performance. The results show that certain [Ru(dpp)3]2+-doped Octyl-triEOS/TEOS composites form uniform, crack-free xerogel films that can be used to construct high-sensitivity O2 sensors that have linear calibration curves and excellent long-term stability. For example, an 11-month-old sensor based on 50 mol % Octyl-triEOS exhibits more than 4-fold greater sensitivity in comparison to an equivalent sensor based on pure TEOS. Over an 11-month time period, the sensitivity of a pure TEOS-based sensor drops by more than 400% whereas a sensor based on 50 mol % Octyl-triEOS remains stable (RSD = 4%).

We report the first biosensor arrays based on pin printing protein-doped xerogels. The individual biosensor elements are on the order of 100 microm in diameter. Arrays are formed (1) onto a planar substrate that is excited by an external source (laser) or (2) directly on the face of a light-emitting diode. We illustrate the potential of our approach by fabricating, testing, and characterizing four types of pin-printed biosensor arrays (PPBSA) for the simultaneous detection of glucose and O2. The analytically reliable operating ranges for the PPBSAs are 0.1-10 mM for glucose and 0.1-100% for O2. The PPBSAs exhibit short- and long-term reproducibilities of no worse than 4 and 8%, respectively. The overall array-to-array response reproducibilities are < or = 12%. These results demonstrate for the first time the combination sol-gel processing and pin printing methods as a way to rapidly form ensembles of integrated, reusable, and stable biosensor arrays for simultaneous multianalyte detection.

A new method to rapidly produce and screen biodegradable polymer- and xerogel-based formulations is described. The approach is based on a high-speed pin printer and imaging with an epi-fluorescence microscope/charge-coupled device detector. By using this approach we can produce and screen over 600 formulations/h and rapidly identify lead formulations and/or compositions that are the most useful for the development of biodegradable devices or (bio)sensors.

We report on the analytical figures of merit for O2-responsive sensor arrays and films formed by sequestering tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) within class II organically modified silicates that are composed of tetramethoxysilane or tetraethoxysilane and monoalkylsiloxanes of the form (CnH(2n+1))-Si-(OR)3 (n = 1-12, R = Me or Et). These sensors exhibit a reasonably linear response to gaseous and dissolved O2 (r2 > 0.99), and the sensor responses are stable for over 2 years. Sensor sensitivity can be tuned continuously by adjusting n. For gas-phase O2 detection, changes in the sensor sensitivity depend primarily on the O2 diffusion coefficient within the xerogel phase. The O2 solubility coefficient within the xerogel phase is also a factor but to a lesser degree. For dissolved O2 detection, changes in the sensor sensitivity depend on the O2 diffusion coefficient and the O2 solubility coefficient within the xerogel phase. A linear correlation also exists between the sensor sensitivity and the polarity within these xerogels. Finally, the feature size of pin-printed sensor elements was found to depend linearly on pin velocity. The results of these experiments demonstrate a new strategy for creating xerogel-based sensor arrays consisting of diversified sensor elements for the same target analyte.