scholarly journals Critical Factors for In Vivo Measurements of Human Skin by Terahertz Attenuated Total Reflection Spectroscopy

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4256
Author(s):  
Lixia Wang ◽  
Sayon Guilavogui ◽  
Henghui Yin ◽  
Yiping Wu ◽  
Xiaofei Zang ◽  
...  
Keyword(s):  
Human Skin ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Deep Penetration ◽  
Reference Spectrum ◽  
Critical Factors ◽  
Contact Duration ◽  
In Vivo Measurements ◽  
Different Types

Attenuated total reflection (ATR) geometry is a suitable choice for in vivo measurements of human skin due to the deep penetration of the field into the sample and since it makes it easy to measure the reference spectrum. On the other hand, there are several critical factors that may affect the terahertz (THz) response in these kinds of experiments. Here, we analyse in detail the influence of the following factors: the contact positions between the thumb and the prism, the contact pressure, the contact duration, and the materials of the prism. Furthermore, we use the THz-ATR technology to evaluate different types of handcream and also establish the theoretical model to investigate the reflectivity after interacting with the skin. The results agree well with experimental ones. Our analysis makes it clear the importance of controlling the above factors during measurements to enable reliable THz response and results which, in turn, may be used to monitor water motion in human skin and to predict possible diseases.

scholarly journals Differential diagnosis of Alzheimer’s disease using spectrochemical analysis of blood

2017 ◽  
Vol 114 (38) ◽  
pp. E7929-E7938 ◽  
Author(s):  
Maria Paraskevaidi ◽  
Camilo L. M. Morais ◽  
Kássio M. G. Lima ◽  
Julie S. Snowden ◽  
Jennifer A. Saxon ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Neurodegenerative Diseases ◽  
Sensitivity And Specificity ◽  
Lewy Bodies ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Repeated Measurements ◽  
Healthy Individuals ◽  
Different Types

The progressive aging of the world’s population makes a higher prevalence of neurodegenerative diseases inevitable. The necessity for an accurate, but at the same time, inexpensive and minimally invasive, diagnostic test is urgently required, not only to confirm the presence of the disease but also to discriminate between different types of dementia to provide the appropriate management and treatment. In this study, attenuated total reflection FTIR (ATR-FTIR) spectroscopy combined with chemometric techniques were used to analyze blood plasma samples from our cohort. Blood samples are easily collected by conventional venepuncture, permitting repeated measurements from the same individuals to monitor their progression throughout the years or evaluate any tested drugs. We included 549 individuals: 347 with various neurodegenerative diseases and 202 age-matched healthy individuals. Alzheimer’s disease (AD;n= 164) was identified with 70% sensitivity and specificity, which after the incorporation of apolipoprotein ε4 genotype (APOEε4) information, increased to 86% when individuals carried one or two alleles of ε4, and to 72% sensitivity and 77% specificity when individuals did not carry ε4 alleles. Early AD cases (n= 14) were identified with 80% sensitivity and 74% specificity. Segregation of AD from dementia with Lewy bodies (DLB;n= 34) was achieved with 90% sensitivity and specificity. Other neurodegenerative diseases, such as frontotemporal dementia (FTD;n= 30), Parkinson’s disease (PD;n= 32), and progressive supranuclear palsy (PSP;n= 31), were included in our cohort for diagnostic purposes. Our method allows for both rapid and robust diagnosis of neurodegeneration and segregation between different dementias.

scholarly journals Infrared Spectroscopy with a Fiber-Coupled Quantum Cascade Laser for Attenuated Total Reflection Measurements Towards Biomedical Applications

Sensors ◽  
2019 ◽  
Vol 19 (23) ◽  
pp. 5130 ◽  
Author(s):  
Ine L. Jernelv ◽  
Karina Strøm ◽  
Dag Roar Hjelme ◽  
Astrid Aksnes
Keyword(s):  
Infrared Spectroscopy ◽  
Quantum Cascade Lasers ◽  
Spectral Power ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Mid Infrared ◽  
Quantum Cascade ◽  
In Vitro Investigation

The development of rapid and accurate biomedical laser spectroscopy systems in the mid-infrared has been enabled by the commercial availability of external-cavity quantum cascade lasers (EC-QCLs). EC-QCLs are a preferable alternative to benchtop instruments such as Fourier transform infrared spectrometers for sensor development as they are small and have high spectral power density. They also allow for the investigation of multiple analytes due to their broad tuneability and through the use of multivariate analysis. This article presents an in vitro investigation with two fiber-coupled measurement setups based on attenuated total reflection spectroscopy and direct transmission spectroscopy for sensing. A pulsed EC-QCL (1200–900 cm − 1 ) was used for measurements of glucose and albumin in aqueous solutions, with lactate and urea as interferents. This analyte composition was chosen as an example of a complex aqueous solution with relevance for biomedical sensors. Glucose concentrations were determined in both setup types with root-mean-square error of cross-validation (RMSECV) of less than 20 mg/dL using partial least-squares (PLS) regression. These results demonstrate accurate analyte measurements, and are promising for further development of fiber-coupled, miniaturised in vivo sensors based on mid-infrared spectroscopy.

scholarly journals Fabrication of Second Skin from Keratin and Melanin

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2568
Author(s):  
Chen Nowogrodski ◽  
Ido Simon ◽  
Shlomo Magdassi ◽  
Oded Shoseyov
Keyword(s):  
Mechanical Properties ◽  
High Resolution ◽  
Human Skin ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Light Transmittance ◽  
Fabrication Method ◽  
Melanin Content ◽  
Toxic Materials ◽  
High Resolution Images

Second skin is a topically applied, skin-conforming material that mimics human skin properties and bears potential cosmetic and e-skin applications. To successfully integrate with natural skin, characteristics such as color and skin features must be matched. In this work, we prepared bio-based skin-like films from cross-linked keratin/melanin films (KMFs), using a simple fabrication method and non-toxic materials. The films retained their stability in aqueous solutions, showed skin-like mechanical properties, and were homogenous and handleable, with non-granular surfaces and a notable cross-linked structure as determined by attenuated total reflection (ATR). In addition, the combination of keratin and melanin allowed for adjustable tones similar to those of natural human skin. Furthermore, KMFs showed light transmittance and UV-blocking (up to 99%) as a function of melanin content. Finally, keratin/melanin ink (KMI) was used to inkjet-print high-resolution images with natural skin pigmented features. The KMFs and KMI may offer advanced solutions as e-skin or cosmetics platforms.

scholarly journals Using ATR-FTIR Spectra and Convolutional Neural Networks for Characterizing Mixed Plastic Waste

2021 ◽  
Author(s):  
Shengli Jiang ◽  
Zhuo Xu ◽  
Medhavi Kamran ◽  
Stas Zinchik ◽  
Sidike Paheding ◽  
...  
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Convolutional Neural Network ◽  
Total Reflection ◽  
Plastic Waste ◽  
Attenuated Total Reflection ◽  
Plastic Materials ◽  
Different Types

<p>We present a convolutional neural network (CNN) framework for classifying different types of plastic materials that are commonly found in mixed plastic waste (MPW) streams. The CNN framework uses experimental ATR-FTIR (attenuated total reflection-Fourier transform infrared spectroscopy) spectra to classify ten different plastic types. We show that the approach reaches accuracies of over 87% and that some plastic types can be perfectly classified.</p>

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