Patrick Hunziker

Label-free protein assay based on a nanomechanical cantilever array

We demonstrate continuous label-free detection of two cardiac biomarker proteins (creatin kinase and myoglobin) using an array of microfabricated cantilevers functionalized with covalently anchored anti-creatin kinase and anti-myoglobin antibodies. This method allows biomarker proteins to be detected via measurement of surface stress generated by antigen–antibody molecular recognition. Reference cantilevers are used to eliminate thermal drifts, undesired chemical reactions and turbulences from injections of liquids by calculating differential deflection signals with respect to sensor cantilevers. The sensitivity achieved for myoglobin detection is below 20 µg ml−1. Both myoglobin and creatin kinase could be detected independently using cantilevers functionalized with the corresponding antibodies, in unspecific protein background. This approach permits the use of up to seven different antigen–antibody reactions simultaneously, including an additional thermomechanical and chemical in situ reference. Applications lie in the field of early and rapid diagnosis of acute myocardial infarction.

Capillary pumps for autonomous capillary systems

Autonomous capillary systems (CSs), where liquids are displaced by means of capillarity, are efficient, fast and convenient platforms for many bioanalytical applications. The proper functioning of these microfluidic devices requires displacing accurate volumes of liquids with precise flow rates. In this work, we show how to design capillary pumps for controlling the flow properties of CSs. The capillary pumps comprise microstructures of various shapes with dimensions from 15-250 microm, which are positioned in the capillary pumps to encode a desired capillary pressure. The capillary pumps are designed to have a small flow resistance and are preceded by a constricted microchannel, which acts as a flow resistance. Therefore, both the capillary pump and the flow resistance define the flow rate in the CS, and flow rates from 0.2-3.7 nL s(-1) were achieved. The placement and the shape of the microstructures in the capillary pumps are used to tailor the filling front of liquids in the capillary pumps to obtain a reliable filling behaviour and to minimize the risk of entrapping air. The filling front can, for example, be oriented vertically or tilted to the main axis of the capillary pump. We also show how capillary pumps having different hydrodynamic properties can be connected to program a sequence of slow and fast flow rates in a CS.

Hands-on time during cardiopulmonary resuscitation is affected by the process of teambuilding: a prospective randomised simulator-based trial

BackgroundCardiac arrests are handled by teams rather than by individual health-care workers. Recent investigations demonstrate that adherence to CPR guidelines can be less than optimal, that deviations from treatment algorithms are associated with lower survival rates, and that deficits in performance are associated with shortcomings in the process of team-building. The aim of this study was to explore and quantify the effects of ad-hoc team-building on the adherence to the algorithms of CPR among two types of physicians that play an important role as first responders during CPR: general practitioners and hospital physicians.MethodsTo unmask team-building this prospective randomised study compared the performance of preformed teams, i.e. teams that had undergone their process of team-building prior to the onset of a cardiac arrest, with that of teams that had to form ad-hoc during the cardiac arrest. 50 teams consisting of three general practitioners each and 50 teams consisting of three hospital physicians each, were randomised to two different versions of a simulated witnessed cardiac arrest: the arrest occurred either in the presence of only one physician while the remaining two physicians were summoned to help (ad-hoc), or it occurred in the presence of all three physicians (preformed). All scenarios were videotaped and performance was analysed post-hoc by two independent observers.ResultsCompared to preformed teams, ad-hoc forming teams had less hands-on time during the first 180 seconds of the arrest (93 ± 37 vs. 124 ± 33 sec, P < 0.0001), delayed their first defibrillation (67 ± 42 vs. 107 ± 46 sec, P < 0.0001), and made less leadership statements (15 ± 5 vs. 21 ± 6, P < 0.0001).ConclusionHands-on time and time to defibrillation, two performance markers of CPR with a proven relevance for medical outcome, are negatively affected by shortcomings in the process of ad-hoc team-building and particularly deficits in leadership. Team-building has thus to be regarded as an additional task imposed on teams forming ad-hoc during CPR. All physicians should be aware that early structuring of the own team is a prerequisite for timely and effective execution of CPR.

Designing switchable nanosystems for medical application.

Within the last decade, nanotechnology has had a major impact on preclinical development in medicine, shaping the emerging scientific field of nanomedicine. Diverse nanomaterial platforms have been introduced as a carrier systems for the delivery of a variety of payloads (e.g. drugs, proteins, peptides, nucleic acids) but additional improvement by stimulus responsiveness would be of tremendous significance. The design of intelligent, stimuli responsive nanosystems promises to expand diagnostic and therapeutic options in medicine by making available an array of highly effective, well tolerated platforms that go beyond simple delivery of drugs or imaging agents. Controlled by internal triggers which may be characteristic for a disease or by external devices that permit tight spatiotemporal control of activity, enhancement of desired therapeutic effects and further suppression of side effects in remote organs may be possible. This review focuses on the toolbox of available internal and external switches suited for the integration into nanoscale carriers and on the clinical experience with stimuli-responsive nano-platforms. A substantial body of evidence shows that internal stimuli including pH, redox potential, enzymatic activity and temperature are suited to trigger nanosystems. For some such systems, clinical trials are in progress, but solid clinical proof of significant patient benefit will be required next. Externally controlled systems include electromagnetically-, temperature-, light-, radiation- and ultrasound triggered systems, and for certain clinical indications, such systems have already proven clinical benefit.

Continuous flow in open microfluidics using controlled evaporation

This paper presents a method for programming the flow rate of liquids inside open microfluidic networks (MFNs). A MFN comprises a number of independent flow paths, each of which starts with an open filling port, has a sealed microchannel in which assays can be performed, and an open capillary pump (CP). The MFN is placed over Peltier elements and its flow paths initially fill owing to capillary forces when liquids are added to the filling ports. A cooling Peltier element underneath the filling ports dynamically prevents evaporation in all filling ports using the ambient temperature and relative humidity as inputs. Another Peltier element underneath the CPs heats the pumps thereby inducing evaporation in the CPs and setting the flow rate in the microchannels. This method achieves flow rates in the microchannels ranging from approximately 1.2 nL s(-1) to approximately 30 pL s(-1), and is able to keep 90% of a 0.6 microL solution placed in an open filling port for 60 min. This simple and efficient method should be applicable to numerous assays or chemical reactions that require small and precise flow of liquids and reagents inside microfluidics.

High-Performance Immunoassays Based on Through-Stencil Patterned Antibodies and Capillary Systems

We present a simple method to pattern capture antibodies (cAbs) on poly(dimethylsiloxane) (PDMS), with high accuracy and in a manner compatible with mass fabrication for use with capillary systems (CSs), using stencils microfabricated in Si. Capture antibodies are patterned as 60-270 microm wide and 2 mm long lines on PDMS and used with CSs that have been optimized for convenient handling, pipetting of solutions, pumping of liquids, such as human blood serum, and visualization of signals for fluorescence immunoassays. With the use of this method, C-reactive protein (CRP) is detected with a sensitivity of 0.9 ng mL(-1) (7.8 pM) in 1 microL of CRP-spiked human serum, within 11 min and using only four pipetting steps and a total volume of sample and reagents of 1.35 microL. This exemplifies the high performances that can be achieved using this approach and an otherwise conventional surface sandwich fluorescence immunoassay. This method is simple and flexible and should therefore be applicable to a large number of demanding immunoassays.

Incidence, risk factors, and outcome of aspiration pneumonitis in ICU overdose patients

ObjectiveTo assess the incidence and outcome of clinically significant aspiration pneumonitis in intensive care unit (ICU) overdose patients and to identify its predisposing factors.DesignRetrospective cohort study.SettingMedical ICU of an academic tertiary care hospital.PatientsAxa0total of 273 consecutive overdose admissions.Measurements and resultsClinically significant aspiration pneumonitis was defined as the occurrence of respiratory dysfunction in axa0patient with axa0localised infiltrate on chest X-ray within 72u202fh of admission. In our cohort we identified 47 patients (17%) with aspiration pneumonitis. Importantly, aspiration pneumonitis was associated with axa0higher incidence of cardiac arrest (6.4 vs 0.9%; pu202f=u202f0.037) and an increased duration of both ICU stay and overall hospital stay [respectively: median 1 (interquartile range 1–3) vs 1 (1–2), pu202f=u202f0.025; and median 2 (1–7) vs 1 (1–3), pu202f<u202f0.001]. In multivariate logistic regression analysis, Glasgow Coma Scale (GCS) score [odds ratio (OR) for each point of GCS 0.8; 95% confidence interval (CI) 0.7–0.9; pu202f=u202f0.001], ingestion of opiates (OR 4.5; 95% CI 1.7–11.6; pu202f=u202f0.002), and white blood cell count (WBC) (OR for each increase in WBC of 109/l 1.05; 95% CI 1.0–1.19; pu202f=u202f0.049) were identified as independent risk factors.ConclusionsClinically relevant aspiration pneumonitis is axa0frequent complication in overdose patients admitted to the ICU. Moreover, aspiration pneumonitis is associated with axa0higher incidence of cardiac arrest and increased ICU and total in-hospital stay.

Succinylcholine versus rocuronium for rapid sequence intubation in intensive care: a prospective, randomized controlled trial

IntroductionSuccinylcholine and rocuronium are widely used to facilitate rapid sequence induction (RSI) intubation in intensive care. Concerns relate to the side effects of succinylcholine and to slower onset and inferior intubation conditions associated with rocuronium. So far, succinylcholine and rocuronium have not been compared in an adequately powered randomized trial in intensive care. Accordingly, the aim of the present study was to compare the incidence of hypoxemia after rocuronium or succinylcholine in critically ill patients requiring an emergent RSI.MethodsThis was a prospective randomized controlled single-blind trial conducted from 2006 to 2010 at the University Hospital of Basel. Participants were 401 critically ill patients requiring emergent RSI. Patients were randomized to receive 1 mg/kg succinylcholine or 0.6 mg/kg rocuronium for neuromuscular blockade. The primary outcome was the incidence of oxygen desaturations defined as a decrease in oxygen saturation ≥ 5%, assessed by continuous pulse oxymetry, at any time between the start of the induction sequence and two minutes after the completion of the intubation. A severe oxygen desaturation was defined as a decrease in oxygen saturation ≥ 5% leading to a saturation value of ≤ 80%.ResultsThere was no difference between succinylcholine and rocuronium regarding oxygen desaturations (succinylcholine 73/196; rocuronium 66/195; P = 0.67); severe oxygen desaturations (succinylcholine 20/196; rocuronium 20/195; P = 1.0); and extent of oxygen desaturations (succinylcholine -14 ± 12%; rocuronium -16 ± 13%; P = 0.77). The duration of the intubation sequence was shorter after succinycholine than after rocuronium (81 ± 38 sec versus 95 ± 48 sec; P = 0.002). Intubation conditions (succinylcholine 8.3 ± 0.8; rocuronium 8.2 ± 0.9; P = 0.7) and failed first intubation attempts (succinylcholine 32/200; rocuronium 36/201; P = 1.0) did not differ between the groups.ConclusionsIn critically ill patients undergoing emergent RSI, incidence and severity of oxygen desaturations, the quality of intubation conditions, and incidence of failed intubation attempts did not differ between succinylcholine and rocuronium.Trial RegistrationClinicalTrials.gov, number NCT00355368.

Unnecessary interruptions of cardiac massage during simulated cardiac arrests.

Background and objective: Cardiopulmonary resuscitation should not be interrupted until the return of spontaneous circulation or the decision to withhold further treatment. There are no data on how consistent in‐hospital cardiopulmonary resuscitation is performed. Accordingly, the aim of the present study was to identify length and type of unnecessary interruptions in simulated cardiac arrests. Methods: The study was carried out in a patient simulator. A scenario of cardiac arrest due to ventricular fibrillation was used. Resuscitation teams consisted of three nurses, a resident and a staff physician. Using videotapes recorded during simulations, the activities of the teams were coded in 5‐s intervals. Unnecessary interruptions were defined as any interruptions in cardiac massage of 10 s or more that were not caused by defibrillation or endotracheal intubation. Results: Twelve teams were studied. The total time of possible cardiac massage was 414 ± 125 s. In each team at least one unnecessary interruption occurred (range 1‐5). Interruptions mounted up to 65 ± 40 s (range 20‐155) or 16 ± 10% (range 5‐41) of the total time of possible cardiac massage. Failure to swiftly resume cardiac massage after an unsuccessful defibrillation accounted for 14 of 39 episodes and for 44 ± 40% of the time of unnecessary interruptions. The debriefings revealed that participants had generally not noticed the unnecessary interruptions during the simulation. Conclusions: The present study identified a significant amount of unnecessary interruptions in cardiac massage. These interruptions were not noticed by the health‐care workers involved.

Autonomous capillary system for one-step immunoassays

Autonomous capillary systems (CSs), in which liquids are transported owing to capillary forces, have been previously used to perform fast and sensitive multi-step immunoassays using minute volumes of analyte. CSs for diagnostic applications have different requirements than CSs that are used as a research tool in life sciences, where a high flexibility and performance prevail over ease of use and portability. In this paper a proof-of-concept for one-step immunoassays based on CSs is demonstrated. This proof-of-concept is based on preloading detection antibodies (dAbs) on the flow path of analytes and redissolving these antibodies to form dAb-analyte complexes, which can be detected using fluorescence downstream on accurately patterned capture antibodies. A user therefore only needs to load a sample at the beginning of a CS and obtains the result of the assay using a conventional fluorescence microscope or scanner. As an example, C-reactive protein was detected in human serum at clinical concentrations within 10xa0min and using only