Colored Tattoo Ink Screening Method with Optical Tissue Phantoms and Raman Spectroscopy.

Due to the increasing popularity of tattoos among the general population, to ensure their safety and quality, there is a need to develop reliable and rapid methods for the analysis of the composition of tattoo inks, both in the ink itself and in already existing tattoos. This paper presents the possibility of using Raman spectroscopy to examine tattoo inks in biological materials. We have developed optical tissue phantoms mimicking the optical scattering coefficient typical for human dermis as a substitute for an in vivo study. The material employed herein allows for mimicking the tattoo-making procedure. We investigated the effect of the scattering coefficient of the matrix in which the ink is located, as well as its chemical compositions on the spectra. Raman surface line scanning has been carried out for each ink in the skin phantom to establish the spatial gradient of ink concentration distribution. This ensures the ability to detect miniature concentrations for a tattoo margin assessment. An analysis and comparison of the spectra of the inks and the tattooed inks in the phantoms are presented. We recommend the utilization of Raman spectroscopy as a screening method to enforce the tattoo ink safety legislations as well as an early medical diagnostic screening tool.

Utilizing pulse dynamics for non-invasive Raman spectroscopy of blood analytes.

Non-invasive measurement methods offer great benefits in the field of medical diagnostics with molecular-specific techniques such as Raman spectroscopy which is increasingly being used for quantitative measurements of tissue biochemistry in vivo. However, some important challenges still remain for label-free optical spectroscopy to be incorporated into the clinical laboratory for routine testing. In particular, non-analyte-specific variations in tissue properties introduce significant variability of the spectra, thereby preventing reliable calibration. For measurements of blood analytes such as glucose, we propose to decrease the interference from individual tissue characteristics by exploiting the known dynamics of the blood-tissue matrix. We reason that by leveraging the natural blood pulse rhythm, the signals from the blood analytes can be enhanced while those from the static components can be effectively suppressed. Here, time-resolved measurements with subsequent pulse frequency estimation and phase-sensitive detection are proposed to recover the Raman spectra correlated with the dynamic changes at blood-pulse frequency. Pilot in vivo study results are presented to establish the benefits as well as outline the challenges of the proposed method in terms of instrumentation and signal processing.

Haemocompatibility of Modified Nanodiamonds.

This study reports the interactions of modified nanodiamond particles in vitro with human blood. Modifications performed on the nanodiamond particles include oxygenation with a chemical method and hydrogenation upon chemical vapor deposition (CVD) plasma treatment. Such nanodiamonds were later incubated in whole human blood for different time intervals, ranging from 5 min to 5 h. The morphology of red blood cells was assessed along with spectral measurements and determination of haemolysis. The results showed that no more than 3% of cells were affected by the nanodiamonds. Specific modifications of the nanodiamonds give us the possibility to obtain nanoparticles which are biocompatible with human blood. They can form a basis for the development of nanoscale biomarkers and parts of sensing systems and devices useful in biomedical environments.

Nanoparticle-free tissue-mimicking phantoms with intrinsic scattering.

We present an alternative to the conventional approach, phantoms without scattering nanoparticles, where scattering is achieved by the material itself: spherical cavities trapped in a silicone matrix. We describe the properties and fabrication of novel optical phantoms based on a silicone elastomer polydimethylsiloxane (PDMS) and glycerol mixture. Optical properties (absorption coefficient µa , reduced scattering coefficient µs' , and anisotropy factor g) of the fabricated phantoms were retrieved from spectrophotometric measurements (in the 400-1100 nm wavelength range) using the inverse adding-doubling method. The internal structure of the phantoms was studied under a scanning electron microscope, and the chemical composition was assessed by Raman spectroscopy. Composition of the phantom material is reported along with the full characterization of the produced phantoms and ways to control their parameters.

Integration of protein tethering in a rapid and label-free SERS screening platform for drugs of abuse.

Surface enhanced Raman spectroscopy (SERS) has emerged as a promising technique for the rapid and ultrasensitive detection of molecular species such as drugs of abuse in biofluids. Yet, it remains a significant challenge to create a viable screening tool for multiple drug classes, owing to the lack of affinity of certain species for the SERS substrate and to the matrix interference in complex media. Here we report a protein tethering SERS approach, which blends plasmonic enhancement with facile drug binding, to engineer a rapid, label-free and versatile screening tool for narcotics. By exploiting the known binding attributes of human serum albumin, we determine the effective concentration of narcotics present in solution through differential enhancement of the spectral markers. In conjunction with chemometric methods, this approach not only enables unambiguous recognition of different drug classes, such as barbiturates, opiates, amphetamines and benzodiazepines, but also offers a lower limit of detection in comparison to direct SERS application. Through molecular docking simulations, we probe the mechanistic underpinnings of the protein tethering approach paving the way for narcotic detection in clinical samples in the near future.

Use of optical skin phantoms for preclinical evaluation of laser efficiency for skin lesion therapy.

Skin lesions are commonly treated using laser heating. However, the introduction of new devices into clinical practice requires evaluation of their performance. This study presents the application of optical phantoms for assessment of a newly developed 975-nm pulsed diode laser system for dermatological purposes. Such phantoms closely mimic the absorption and scattering of real human skin (although not precisely in relation to thermal conductivity and capacitance); thus, they can be used as substitutes for human skin for approximate evaluation of laser heating efficiency in an almost real environment. Thermographic imaging was applied to measure the spatial and temporal temperature distributions on the surface of laser-irradiated phantoms. The study yielded results of heating with regard to phantom thickness and absorption, as well as laser settings. The methodology developed can be used in practice for preclinical evaluations of laser treatment for dermatology.

Measurements of fundamental properties of homogeneous tissue phantoms.

We present the optical measurement techniques used in human skin phantom studies. Their accuracy and the sources of errors in microscopic parameters' estimation of the produced phantoms are described. We have produced optical phantoms for the purpose of simulating human skin tissue at the wavelength of 930 nm. Optical coherence tomography was used to measure the thickness and surface roughness and to detect the internal inhomogeneities. A more detailed study of phantom surface roughness was carried out with the optical profilometer. Reflectance, transmittance, and collimated transmittance of phantoms were measured using an integrating-sphere spectrometer setup. The scattering and absorption coefficients were calculated with the inverse adding-doubling method. The reduced scattering coefficient at 930 nm was found to be 1.57±0.14 mm(−1) and the absorption was 0.22±0.03 mm(−1) . The retrieved optical properties of phantoms are in agreement with the data found in the literature for real human tissues.