3D‐Bioprinted Phantom with Human Skin Phototypes for Biomedical Optics

Abstract

Skin consists of a lamellar structure with diverse cell types (e.g., immune cells, melanocytes, and basal cells) that periodically detach from the basement membrane, move to the surface, and die for self-renewal. [3] Melanocytes are a critical cell type that generate melanin to absorb UV light (290-400 nm), which is a major risk for skin diseases (e.g., melanoma) due to DNA damage. [4][5][6][7] Here, melanin-containing organelles called melanosomes are transferred to the surrounding keratinocytes. This increase in melanosome concentration leads to darker skin phototypes, and darker phototypes can be a function of racial background or previous sun exposure, that is, tanning. [8] Indeed, skin pigmentation depends on variations in the size, number, clustering phase, and the proportions between melanin species (e.g., eumelanin and pheomelanin). [9] Skin pigmentation has been quantified using melanosome volume fraction (M f ) parameter: 1.3-6.3% for lightly pigmented adults, 11-16% for moderately pigmented adults, and 18-43% for darkly pigmented adults. [10] Variations in skin phototypes can complicate biomedical optics. Melanin absorption increases linearly from 800 to 600 nm and exponentially from 600 to 300 nm. [11,12] Darker skin phototypes can absorb and scatter more photons: as a result, incident light is attenuated before it reaches the target of interest, and signal transmission can be impeded back to the sensor. Therefore, variations in skin phototypes have negatively affected many forms of medical optic technology including pulse oximetry, [13,14] cerebral tissue oximeters, [15] optical coherence tomography, [16] wearable electronics, [17][18][19] photoacoustic (PA) imaging, [20] fluorescence imaging, [21] and photothermal therapy. [22] One recent study compared 48 097 pairs of oxygen saturation levels measured by pulse oximetry and arterial blood gas test obtained from 8675 white patients and 1326 black patients. [13] The results found that pulse oximetry had trouble in diagnosing hypoxemia in 11% Black patients and 3% white patients due to light absorption by melanin. [13,14] Furthermore, wearable electronics (e.g., smartwatches) have reported inaccuracies in heart rate readings occurring more often in users with dark skin than light skin. [17,18] Clearly, the impact of differences in skin phototypes underscore the ongoing need to understand and correct racial bias in optical technologies. While larger 3D-bioprinted skin-mimicking phantoms with skin colors ranging across the Fitzpatrick scale are reported. These tools can help understand the impact of skin phototypes on biomedical optics. Synthetic melanin nanoparticles of different sizes (70-500 nm) and clusters are fabricated to mimic the optical behavior of melanosome. The absorption coefficient and reduced scattering coefficient of the phantoms are comparable to real human skin. Further the melanin content and distribution in the phantoms versus real human skins are validated via photoacoustic (PA) imaging. The PA signal of the phantom can be improved ...

Endoproteolysis of Oligopeptide-Based Coacervates for Enzymatic Modeling

“…This correlation is attributed to the energy dissipation via nonradiative decay (or heat) following light absorption. 46 The decrease in the quantum yield (QY) from 0.16 for the free dye to 0.05 also supports the observed PL quenching (Table S2). Our group has reported near-complete self-quenching of the dye PL and enhanced PA signal through aggregation-associated interactions, realized by bringing a dye dimer in close proximity using a short linker.…”

“…In Figure c, the coacervates show a 2- to 4-fold PA enhancement over the disassembled samples across three tested dye concentrations. This correlation is attributed to the energy dissipation via nonradiative decay (or heat) following light absorption . The decrease in the quantum yield (QY) from 0.16 for the free dye to 0.05 also supports the observed PL quenching (Table S2).…”

“…Figure a,b shows the immediate optical differences of Cy5.5 upon incorporation into coacervate. The introduction of 1% w/v SDS (above CMC) to coacervates is 2-fold: (i) it breaks the ion-pairing interactions and disassembles the coacervates, and (ii) it minimizes dye–dye stacking interactions and favors its monomeric state. , The absorbance peak wavelength (λ max ) of Cy5.5 in coacervates blue-shifts from 687 nm for the monomeric dye to 677 nm, indicating strong intermolecular interactions of Cy5.5 . This shift is accompanied by the intensity reductions of the hypochromic peak and peak broadening.…”

Goldilocks Energy Minimum: Peptide-Based Reversible Aggregation and Biosensing

“…To induce reversible aggregation of the AuNPs, we used positively charged Arg- and Lys-based peptide residues (i.e., RRK). The RRK peptide could induce plasmonic coupling by electrostatic attractions between negatively charged citrate molecules and guanidine and amine groups in RRK (Figure a). , The size of AuNPs increased upon addition of RRK peptides, as confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) (Figures b and S1). UV–vis spectroscopy showed that the plasmonic resonance peak (520 nm) of AuNPs redshifted to 648 nm; visually, the sample changed color from red to blue (Figure c).…”

A novel CT-responsive hydrogel for the construction of an organ simulation phantom for the repeatability and stability study of radiomic features

“…[14][15][16][17] Nevertheless, although most reported phantom materials boast stability advantages, [18][19][20] they exhibit poor repeatability and limited CT similarity to human tissue. 16,21 These materials lack adequate CT control performance, as their single X-ray attenuation characteristics can only absorb fixed Xray energy. Consequently, researchers are actively seeking an exceptional function phantom that combines feature stability, repeatability, CT similarity, and repeatable texture.…”