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Diagnostics, Volume 2, Issue 4 (December 2012) – 6 articles , Pages 42-106

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10122 KiB

Open AccessArticle

Detection of Dissolved Lactose Employing an Optofluidic Micro-System

by Emanuel Weber, Franz Keplinger and Michael J. Vellekoop

Diagnostics 2012, 2(4), 97-106; https://doi.org/10.3390/diagnostics2040097 - 6 Dec 2012

Cited by 5 | Viewed by 7494

Abstract

In this work, a novel optofluidic sensor principle is employed for a non-invasive and label-free characterization of lactose containing liquid samples. Especially for medicine and food industry, a simple, fast and accurate determination of the amount of lactose in various products is highly desirable. The presented system exploits the impact of dissolved molecules on the refractive index for sample characterization. On the optofluidic chip, a microfluidic channel filled with the analyte is hit by slightly diverging laser light. The center incident angle of the beam on-chip is set close to the critical angle for total internal reflection. Both the reflected and the transmitted light signals are recorded at the solid-liquid interface. The ratio of those two signals is then used as representative value for the analyte. Using this principle, lactose containing samples were differentiated based on their concentrations at a step size of 10 mmol/L. The use of the signals ratio instead of a single signal approach improves the stability of the system significantly, allowing for higher resolutions to be achieved. Furthermore, the fabrication of the devices in PDMS ensures biocompatibility and provides low absorbance of light in the visible range. Full article

(This article belongs to the Special Issue Microfluidic Lab-on-a-Chip Platforms for High-Performance Diagnostics)

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825 KiB

Open AccessReview

Cell-Based Biosensors: Electrical Sensing in Microfluidic Devices

by Katrine Kiilerich-Pedersen and Noemi Rozlosnik

Diagnostics 2012, 2(4), 83-96; https://doi.org/10.3390/diagnostics2040083 - 6 Dec 2012

Cited by 24 | Viewed by 10513

Abstract

Cell-based biosensors provide new horizons for medical diagnostics by adopting complex recognition elements such as mammalian cells in microfluidic devices that are simple, cost efficient and disposable. This combination renders possible a new range of applications in the fields of diagnostics and personalized medicine. The review looks at the most recent developments in cell-based biosensing microfluidic systems with electrical and electrochemical transduction, and relevance to medical diagnostics. Full article

(This article belongs to the Special Issue Microfluidic Lab-on-a-Chip Platforms for High-Performance Diagnostics)

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716 KiB

Open AccessArticle

Gold Nanoparticles-Coated SU-8 for Sensitive Fluorescence-Based Detections of DNA

by Cuong Cao, Sam W. Birtwell, Jonas Høgberg, Hywel Morgan, Anders Wolff and Dang Duong Bang

Diagnostics 2012, 2(4), 72-82; https://doi.org/10.3390/diagnostics2040072 - 29 Nov 2012

Cited by 10 | Viewed by 10147

Abstract

SU-8 epoxy-based negative photoresist has been extensively employed as a structural material for fabrication of numerous biological microelectro-mechanical systems (Bio-MEMS) or lab-on-a-chip (LOC) devices. However, SU-8 has a high autofluorescence level that limits sensitivity of microdevices that use fluorescence as the predominant detection workhorse. Here, we show that deposition of a thin gold nanoparticles layer onto the SU-8 surface significantly reduces the autofluorescence of the coated SU-8 surface by as much as 81% compared to bare SU-8. Furthermore, DNA probes can easily be immobilized on the Au surface with high thermal stability. These improvements enabled sensitive DNA detection by simple DNA hybridization down to 1 nM (a two orders of magnitude improvement) or by solid-phase PCR with sub-picomolar sensitivity. The approach is simple and easy to perform, making it suitable for various Bio-MEMs and LOC devices that use SU-8 as a structural material. Full article

(This article belongs to the Special Issue Microfluidic Lab-on-a-Chip Platforms for High-Performance Diagnostics)

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997 KiB

Open AccessArticle

Prenatal Diagnosis of Chromosome Abnormalities: A 13-Year Institution Experience

by Carmen Comas, Mónica Echevarria, María Ángeles Rodríguez, Ignacio Rodríguez, Bernat Serra and Vincenzo Cirigliano

Diagnostics 2012, 2(4), 57-71; https://doi.org/10.3390/diagnostics2040057 - 19 Nov 2012

Cited by 3 | Viewed by 9397

Abstract

Objective: To analyze trends in screening and invasive prenatal diagnosis of chromosome abnormalities (CA) over a 13-year period and correlate them to changes in the national prenatal screening policy. Methods: We retrospectively reviewed Down syndrome (DS) screening tests and fetal karyotypes obtained by prenatal invasive testing (IT) in our fetal medicine unit between January 1999 and December 2011. Results: A total of 24,226 prenatal screening tests for DS and 11,045 invasive procedures have been analyzed. Over a 13-year period, utilization of non-invasive screening methods has significantly increased from 57% to 89%. The percentage of invasive procedures has declined from 49% to 12%, although the percentage of IT performed for maternal anxiety has increased from 22% to 55%. The percentage of detected CA increased from 2.5% to 5.9%. Overall, 31 invasive procedures are needed to diagnose 1 abnormal case, being 23 procedures in medical indications and 241 procedures in non-medical indications. Conclusions: Our experience on screening and invasive prenatal diagnostic practice shows a decrease of the number of IT, with a parallel decline in medical indications. There is an increasing efficiency of prenatal screening program to detect CA. Despite the increasing screening policies, our population shows a growing request for prenatal IT. The a priori low risk population shows a not negligible residual risk for relevant CA. This observation challenges the current prenatal screening strategy focused on DS; showing that the residual risk is higher than the current cut-off used to indicate an invasive technique. Full article

(This article belongs to the Special Issue Advance in Prenatal Diagnosis)

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139 KiB

Open AccessCommunication

Visual Suppression is Impaired in Spinocerebellar Ataxia Type 6 but Preserved in Benign Paroxysmal Positional Vertigo

by Masahiko Kishi, Ryuji Sakakibara, Tomoe Yoshida, Masahiko Yamamoto, Mitsuya Suzuki, Manabu Kataoka, Yohei Tsuyusaki, Akihiko Tateno and Fuyuki Tateno

Diagnostics 2012, 2(4), 52-56; https://doi.org/10.3390/diagnostics2040052 - 11 Oct 2012

Cited by 6 | Viewed by 5838

Abstract

Positional vertigo is a common neurologic emergency and mostly the etiology is peripheral. However, central diseases may mimic peripheral positional vertigo at their initial presentation. We here describe the results of a visual suppression test in six patients with spinocerebellar ataxia type 6 (SCA6), a central positional vertigo, and nine patients with benign paroxysmal positional vertigo (BPPV), the major peripheral positional vertigo. As a result, the visual suppression value of both diseases differed significantly; e.g., 22.5% in SCA6 and 64.3% in BPPV (p < 0.001). There was a positive correlation between the visual suppression value and disease duration, cerebellar atrophy, and CAG repeat length of SCA6 but they were not statistically significant. In conclusion, the present study showed for the first time that visual suppression is impaired in SCA6, a central positional vertigo, but preserved in BPPV, the major peripheral positional vertigo, by directly comparing both groups. The abnormality in the SCA6 group presumably reflects dysfunction in the central visual fixation pathway at the cerebellar flocculus and nodulus. This simple test might aid differential diagnosis of peripheral and central positional vertigo at the earlier stage of disease. Full article

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471 KiB

Open AccessArticle

Importance of Attenuation Correction (AC) for Small Animal PET Imaging

by Henrik H. El Ali, Rasmus Poul Bodholdt, Jesper Tranekjær Jørgensen, Rebecca Myschetzky and Andreas Kjaer

Diagnostics 2012, 2(4), 42-51; https://doi.org/10.3390/diagnostics2040042 - 9 Oct 2012

Cited by 22 | Viewed by 10465

Abstract

The purpose of this study was to investigate whether a correction for annihilation photon attenuation in small objects such as mice is necessary. The attenuation recovery for specific organs and subcutaneous tumors was investigated. A comparison between different attenuation correction methods was performed. Methods: Ten NMRI nude mice with subcutaneous implantation of human breast cancer cells (MCF-7) were scanned consecutively in small animal PET and CT scanners (MicroPET^TM Focus 120 and ImTek’s MicroCAT^TM II). CT-based AC, PET-based AC and uniform AC methods were compared. Results: The activity concentration in the same organ with and without AC revealed an overall attenuation recovery of 9–21% for MAP reconstructed images, i.e., SUV without AC could underestimate the true activity at this level. For subcutaneous tumors, the attenuation was 13 ± 4% (9–17%), for kidneys 20 ± 1% (19–21%), and for bladder 18 ± 3% (15–21%). The FBP reconstructed images showed almost the same attenuation levels as the MAP reconstructed images for all organs. Conclusions: The annihilation photons are suffering attenuation even in small subjects. Both PET-based and CT-based are adequate as AC methods. The amplitude of the AC recovery could be overestimated using the uniform map. Therefore, application of a global attenuation factor on PET data might not be accurate for attenuation correction. Full article

(This article belongs to the Collection Feature Papers)

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