Perfusion Microfermentor Integrated into a Fiber Optic Quasi-Elastic Light Scattering Sensor for Fast Screening of Microbial Growth Parameters.

This research presents a microfermentor integrated into an optical fiber sensor based on quasi-elastic light scattering (QELS) to monitor and swiftly identify cellular growth kinetic parameters. The system uses a 1310 nm laser light that is guided through single-mode silica optical fibers to the interior of perfusion chambers, which are separated by polycarbonate membranes (470 nm pores) from microchannels, where a culture medium flows in a constant concentration. The system contains four layers, a superior and an inferior layer made of glass, and two intermediate poly(dimethylsiloxane) layers that contain the microchannels and the perfusion chambers, forming a reversible microfluidic device that requires only the sealing of the fibers to the inferior glass cover. The QELS autocorrelation decay rates of the optical signals were correlated to the cells counting in a microscope, and the application of this microsystem to the monitoring of alcoholic fermentation of Saccharomyces cerevisiae resulted in the kinetic parameters of KM = 4.1 g/L and µm = 0.49 h-1. These results agree with both the data reported in the literature and with the control batch test, showing that it is a reliable and efficient biological monitoring system.

Evaluation of image matching techniques for optical fiber specklegram sensor analysis.

A quantitative study of image matching techniques applied to fiber specklegram sensor analysis is presented. The fiber status is modulated by a microbending transducer, so the output speckle field can be correlated to the input displacements. Once acquired and preprocessed, the specklegrams' variations were evaluated according to seven approaches. Although the average intensity did not provide reliable information per se, the correlation and sum of differences methods yielded ∼11 mm-1 and ∼14 mm-1 sensitivities, respectively, within a ∼0.06 mm range and low linearity and hysteresis errors, with enhancement possibility by intensity level cancellation. Moreover, the phase-only correlation and the mutual information metrics provided very high sensitivities (22 mm-1 and 120 mm-1, respectively) for a <0.02 mm range, making these techniques suitable for detecting subtle variations in the fiber status due to physical or chemical stimuli.

Optical fiber specklegram sensor analysis by speckle pattern division.

An optical fiber specklegram sensor interrogation method based on speckle pattern fragmentation is presented. The acquired specklegram images are divided in a square grid, creating sub-images that are further processed by a correlation technique, allowing the quantification of localized changes in the specklegrams. The methodology was tested on the assessment of linear displacements using a microbending transducer, by evaluating different grid sizes. For a 5×5 grid, a 2.53 mm-1 sensitivity over a 0.27 mm range was obtained, representing an extension of 237.5% in comparison to the standard interrogation technique. Therefore, the presented technique allows enhancing the sensor dynamic range without modifying the experimental setup.

In vitro assessment of the Apico Aortic Blood Pump: anatomical positioning, hydrodynamic performance, hemolysis studies, and analysis in a hybrid cardiovascular simulator.

The Apico Aortic Blood Pump (AABP) is a centrifugal continuous flow left ventricular assist device (LVAD) with ceramic bearings. The device is in the initial development phase and is being designed to be attached directly to the left ventricular apex by introducing an inlet cannula. This paper reports results from in vitro experiments. In order to evaluate implantation procedures and device dimensioning, in vitro experiments included an anatomic positioning study for the analysis of surgical implantation procedure and device dimensions and positioning that was performed using the body of a pig. The results revealed no damage caused by the device, and the surgical implantation procedure was considered feasible. Hydrodynamic performance curves were obtained to verify the applicability of the device as an LVAD, showing adequate performance. Mechanical blood trauma was analyzed through 6-h hemolysis tests, with total pressure head of 100 mm Hg and flow of 5 L/min. Mean normalized index of hemolysis was 0.009 g/100 L (±0.002 g/100 L). Studies using a hybrid cardiovascular simulator were conducted for three types of circulatory conditions: normal healthy conditions, concentric hypertrophic heart failure (CHHF), and CHHF with AABP assistance. Analysis of cardiovascular parameters under those three conditions demonstrated that when the AABP was assisting the system, parameters under CHHF conditions went back to normal healthy values, indicating the AABP's effectiveness as CHHF therapy. Our preliminary results indicate that it is feasible to use the AABP as a LVAD. The next steps include long-term in vivo experiments.

In vitro assessment of the apico aortic blood pump: anatomical positioning, hydrodynamic performance, hemolysis studies, and analysis in a hybrid cardiovascular simulator

Abstract: The Apico Aortic Blood Pump (AABP) is acentrifugal continuous flow left ventricular assist device(LVAD) with ceramic bearings. The device is in the initialdevelopment phase and is being designed to be attacheddirectly to the left ventricular apex by introducing an inletcannula. This paper reports results from in vitro experiments.In order to evaluate implantation procedures anddevice dimensioning, in vitro experiments included an anatomicpositioning study for the analysis of surgical implantationprocedure and device dimensions and positioningthat was performed using the body of a pig. The resultsrevealed no damage caused by the device, and the surgicalimplantation procedure was considered feasible. Hydrodynamicperformance curves were obtained to verify theapplicability of the device as an LVAD, showing adequateperformance. Mechanical blood trauma was analyzedthrough 6-h hemolysis tests, with total pressure head of100 mm Hg and flow of 5 L/min. Mean normalized index ofhemolysis was 0.009 g/100 L (±0.002 g/100 L).Studies usinga hybrid cardiovascular simulator were conducted for threetypes of circulatory conditions: normal healthy conditions,concentric hypertrophic heart failure (CHHF), and CHHFwith AABP assistance. Analysis of cardiovascular parametersunder those three conditions demonstrated that whenthe AABP was assisting the system, parameters underCHHF conditions went back to normal healthy values, indicatingthe AABP’s effectiveness as CHHF therapy. Ourpreliminary results indicate that it is feasible to use theAABP as a LVAD. The next steps include long-term invivo experiments.