Utilizing a commercial RNAse activity assay, we discover collagen type I, isolated from rat tail, includes intrinsic nucleases activity as indicated with the emission top at ~520 nm. nuclease-rich conditions (undiluted serum) with no need for prior test planning or oligonucleotide adjustment. The usage of collagen being a biocompatible membrane represents an over-all method of compatibly user interface E-AB receptors with complex natural samples. showed the effectiveness of locked nucleic acids (LNAs), to create a nuclease-insensitive ricin-selective RNA aptamer.12 This technique required engineering of the ricin-selective aptamer modified with 2-O-4C-methylene-engineered an RNA aptamer particular for tumor necrosis aspect by updating the non-bridging oxygens over the backbone of the oligonucleotide with sulfur, producing a phosphorothioate.3 This modification inhibits nuclease hydrolysis and cleavage mechanisms of P-O bonds, but again requires complicated chemical modification of the aptamer. As an alternative to chemical modification, Ferapontova demonstrated that a theophylline-selective RNA E-AB sensor exposed to previously-centrifuged (~3000 Da molecular weight-cutoff filter) blood serum sample exhibited a strong electrochemical transmission.13 Jarczewska, demonstrated the usefulness of RNA aptamers to quantify the malignancy biomarker urokinase plasminogen activator (uPA) in bovine serum albumin (BSA). Briefly, the substitution of the 2-hydroxyl group of the ribose ring with a halogen (fluorine) allowed experimental measurements, inhibiting nuclease hydrolysis of the P-O bond of the nucleoside.14 The newly developed 2-fluoro-pyridine RNA aptamer demonstrated nuclease resistant properties and improved the robustness of the ribonucleotide single-stranded sequence. All methodologies successfully enable RNA-based sensor function in nuclease-rich environments but require oligonucleotide redesign or time-consuming sample pretreatment. More recently, we exhibited the usefulness of a polyacrylamide hydrogel membrane to passively protect an aminoglycoside-specific aptamer from nuclease activity in untreated serum.15 This method demonstrated an initial 30% signal electrochemical signal before stabilizing with the copolymerization of acrylamide and bisacrylamide and only provided protection for any short-time period. In the present work, we demonstrate for the first time the use of a collagen hydrogel with ribonuclease inhibitor entrapped in the gel network to protect small molecule RNA-based E-AB sensors Besifloxacin HCl for at least 6 hours maintaining sensor function. To demonstrate this, an E-AB sensor we employed an designed RNA sequence for the sensitive and specific detection of aminoglycoside antibiotics.16 Specifically, we Besifloxacin HCl find that this RNA-based sensors are guarded by a collagen hydrogel formed in the presence of ribonuclease inhibitor (RI) with the sensors exhibiting no appreciable change in signal upon employment in unadulterated serum. The protection enables a quantitative Rabbit polyclonal to AREB6 titration directly in unadulterated serum representing the first demonstration of such in untreated serum with native RNA. Furthermore, we find that this collagen membrane does not appreciably impact the signaling abilities of the sensor, and thus the sensors respond quantitatively to the aminoglycoside antibiotic tobramycin. Given the generality and compatibility of forming collagen membranes, we believe this to be a general approach to protecting RNA-based sensors. EXPERIMENTAL SECTION Chemicals and solutions Tris-2-carboxyehyl-phosphine (TCEP), 6-mercapto-1-hexanol (99%), Trizma base (2-amino-2-(hydroxymethyl)-1,3-propanediol, magnesium chloride (MgCl2), sodium chloride (NaCl), tobramycin (Tob), ferrocene carboxylic acid, 97% (FCC), sulfuric acid (H2SO4), and 10X Tris-EDTA buffer, Dulbeccos altered Eagles medium (DMEM), sodium hydroxide (NaOH), sodium acetate (NaOAC) Tetrabutylammonium hexafluorophosphate (TBAPF6), ferrocene (FC) Fetal Bovine Serum (FBS), and Protector RNase Inhibitor were all used as received from Sigma-Aldrich. Hydrogen peroxide 30%, 95% ethanol, and 10x PBS buffer were used as received (Fischer Scientific). Collagen I from rat tail was used as received (Gibco). Ambion RNaseAlert QC System was Besifloxacin HCl used as obtained from Thermo Fischer Scientific. SP Sepharose Fast Circulation was used as received from GE Healthcare Life Sciences. All solutions were prepared using autoclaved, ultrapure water (18.0 M cm at 25 C) using a Biopak Polisher Millipore ultra-purification system (Millipore, Billerica, MA). The RNA aminoglycoside aptamer sequence (5-HSC6-CUUGGUUUAGGUAAUGAG-MB-3 (D2 Sequence)16 was purified using dual-HPLC (Biosearch Technologies, CA) and used as received. Electrode fabrication and characterization The chip electrodes were fabricated on a 76.2 mm diameter borofloat glass wafer (WRS Materials, San Jose, CA) comprising 3 square working Au electrodes (4 mm2), one square Au quasi-reference electrode (4 mm2), and an Besifloxacin HCl Au counter electrode (21 m2) (Determine S1). Chips were fabricated using standard photolithography techniques. Briefly, thin films of chromium and platinum (50 and 1000 ?, respectively) were deposited.