Investigation into the effect that probe immobilisation method type has on the analytical signal of an EIS DNA biosensor.

The analytical performance of an enhanced surface area electrolyte insulator semiconductor (EIS) device was investigated for DNA sensor development. The work endeavored to advance EIS performance by monitoring the effect of DNA probe layers have on the impedimetric signal during target hybridisation detection. Two universally employed covalent chemistries, direct and spacer-mediated attachment of amino modified probe molecules to amino-functionalised surfaces were investigated. Relative areal densities of immobilised probe were measured on planar and enhanced surface area substrates using epi-fluorescence microscopy. The reproducibility of the each immobilisation method was seen to have a direct effect on the reproducibility of the impedimetric signal. The sensitivity and selectivity was seen to be dependent on the type of immobilisation method. Real time, impedimetric detection of target DNA hybridisation concentrations as low as 25 and 1 nM were possible. The impact that probe concentration had on the impedimetric signal for selective and non-selective interactions was also investigated.

Microporous silicon and biosensor development: structural analysis, electrical characterisation and biocapacity evaluation.

An investigation of the fabrication of microporous silicon (MPS) layers as a material for the development of an electrolyte insulator semiconductor (EIS) capacitance sensor has been performed. The goal was to create a high surface area substrate for the immobilisation of biorecognition elements. Structural analysis of MPS layers as a function of key etch parameters, namely implant type (p or n), implant dose, hydrofluoric acid (HF) etch concentration and current density has been performed using scanning electron microscopy (SEM). It was possible to image porous layers with average pore diameter as low as 4 nm. n-type silicon samples had larger pore networks than p-type samples and reducing the silicon resistivity led to a reduction in the pores per microm2. It was found that increasing the HF etch concentration reduced the average pore diameter and increased the pores per microm2. Increasing the current density at which the etch was performed has the same effect. Understanding the effect of these parameters allows the MPS layer to be tuned to match specifications for optimum biocapacity. Different MPS layers were electrically characterised using capacitance-voltage and capacitance-frequency sweeps, in order to determine the effect of porosity on increases in surface area. The measured capacitance increased with increasing pores per microm2. p-type silicon with a boron implant in the back of the wafer, which had been etched in 25% HF in ethanol at a current density of 75 mA/cm2 yielded the highest capacitance signal per unit area. The effect of porosity and pore size on the biocapacity of the samples was also determined. For avidin immobilisation, with pores sizes above 5 nm, as the porosity increased the biocapacity increased. MPS fabricated in p-type silicon with a front and back implant etched in 25% HF at a current density of 25 mA/cm2 was used for the capacitance detection of synthetic oligonucleotides.

Positive impact of an interdisciplinary chest pain initiative on traditionally underserved populations.

BACKGROUND: We assessed the clinical impact of an interdisciplinary, cardiac nurse practitioner-facilitated chest pain (CP) initiative that stresses an early invasive approach for patients with CP with acute coronary syndromes in traditionally underserved patient populations, including females, blacks, Hispanics, and patients older than 60 years. METHODS: Two groups of patients were identified: Pre-CP initiative (December 1999-February 2000) and post-CP initiative (December 2000-February 2001). RESULTS: Analysis of 714 patients revealed significantly more cardiac diagnoses post-CP initiative (61% pre-CP initiative vs. 73% post-CP initiative, P = 0.002), including in patients with myocardial infarction (MI) who were older than 60 years, females, and Hispanics. There was a significant increase in rates of cardiac catheterizations within 1 week of admission (10.5% vs. 20.4%, P <0.001), including in Hispanics. For rates of coronary artery stenting and/or bypass grafting (CABG), there was also a significant increase post-CP initiative (2.5% vs. 10.1%, P = 0.0005), as well as for Hispanics. Length of stay was significantly reduced for patients older than 60 years (8.3 vs. 5.8 days, P = 0.002). CONCLUSION: Establishment of an interdisciplinary, cardiac nurse practitioner-facilitated CP initiative is associated with improvement in several clinical processes and outcomes: increased cardiac disease diagnosis in females, Hispanics, and patients older than 60 years; increased rates of cardiac catheterizations in Hispanic patients, increased rates of coronary artery stenting and/or CABG, particularly in Hispanic patients; and decreased length of stay in patients older than 60 years. These data support a targeted interdisciplinary CP initiative as a strategy to systematically enhance access to cardiovascular diagnosis in underserved patient populations.

A rapid-response alphanumeric paging design decreases door-to-balloon times in patients undergoing primary percutaneous coronary intervention for ST elevation acute myocardial infarction.

INTRODUCTION: In acute ST elevation myocardial infarction (STEMI), rapid reperfusion of the infarcted artery improves cardiovascular outcomes; however, many hospitals have difficulty achieving recommended times. We hypothesized that a Rapid-Response Alphanumeric Paging Design (RAPiD) would reduce door-to-balloon time for primary percutaneous coronary intervention (PCI) in STEMI. METHODS: A chest pain algorithm and interdisciplinary team was established in December 2000. In August 2002, RAPiD was instituted to transmit the diagnosis and location of a STEMI to the chest pain team through a speed-dial button. All patients presenting to our emergency department from February 2002 through July 2003 with STEMI were included. Exclusion criteria included lack of chest pain, cardiopulmonary arrest before PCI, and catheterization or PCI not performed. Outside-referral STEMI, in-patient STEMI, and failed thrombolysis patients were excluded. Data was obtained from medical records. Log transform of door-to-balloon (DTB) times was performed. RESULTS: Forty-seven events satisfied inclusion and exclusion criteria with 32 occurring after RAPiD (post-RAPiD). Fifteen events occurred during on-hours (8 am to 7 pm on weekdays). Mean untransformed DTB times pre- and post-RAPiD were 162 +/- 137 (standard deviation) minutes and 112 +/- 41 minutes. The main effects analysis of variance model showed a significant reduction in post-RAPiD DTB time (P = 0.03) with a mean reduction of 26% during off-hours and 20% during on-hours. The post-RAPiD estimate of mean DTB time, derived from the antilog of the log transform, was 96.7 minutes (95% confidence interval, 83.7-111.7). CONCLUSIONS: The institution of RAPiD in a hospital with a preexisting chest pain algorithm significantly decreases DTB times so as to satisfy current ACC/AHA guidelines.

Value of definitive diagnostic testing in the evaluation of patients presenting to the emergency department with chest pain.

The optimal diagnostic evaluation of patients presenting to the emergency department (ED) with chest pain but without myocardial infarction or unstable angina is controversial. We performed a prospective, nonrandomized, observational study of 1,195 consecutive patients presenting to the ED with chest pain but who had normal or nondiagnostic electrocardiograms and negative cardiac biomarkers. Patients (mean +/- SD age 61 +/- 15 years; 55% women) were admitted to the hospital and a standard protocol for evaluation and treatment was suggested. The use of stress myocardial perfusion imaging (MPI) or cardiac catheterization during their index hospitalization, and the 3-month incidence of coronary angiography, percutaneous cardiac intervention, coronary artery bypass surgery, re-presentation to our institution's ED for chest pain, myocardial infarction, or death were followed. Five hundred nine of 1,195 patients (43%) underwent provocative stress MPI during their index hospitalization; 37% had perfusion defects (predominantly ischemia). Fifty-six of 1,195 patients (4%) underwent cardiac catheterization without stress MPI for their primary diagnostic evaluation. Six hundred thirty of 1,195 patients (53%) had neither MPI or cardiac catheterization during their index hospitalization. During the 3-month follow-up period, patients with a normal stress perfusion study during their index hospitalization had fewer return visits (4%) compared with patients with abnormal perfusion studies (19%), those who underwent catheterization directly (16%), or patients with no initial diagnostic evaluation (15%) (p <0.001). In addition, patients who had a diagnostic evaluation during their index hospitalization had a lower incidence of either acute myocardial infarction (0.9% vs 2.1%) or death (0.4% vs 3.0%, p <0.001) in the 3-month follow-up period. Accordingly, we strongly advocate provocative stress MPI early after presentation for chest pain in all patients with risk factors for coronary artery disease.

Design of a comprehensive chest pain initiative in an academic urban hospital.

We describe the development and institution of an initiative based on a clinical diagnostic algorithm and treatment pathways, facilitated by cardiac nurse practitioners, for the treatment of the diverse group of patients with chest pain who seek treatment at our urban-based institution. We believe that our chest pain initiative incorporates previous strategies of rapid emergency department management with inpatient-based care while providing a framework for outpatient follow-up and secondary prevention. These strategies allow our hospital to meet its goals of providing chest pain patients with standardized, high-quality, and expeditious care, given the challenges faced by an academic urban hospital.