Development of a novel laboratory photodynamic therapy device: automated multi-mode LED system for optimum well-plate irradiation.

Photodynamic therapy (PDT) is a targeted treatment method that utilizes a photosensitizer (PS) to induce cytotoxicity in malignant and non-malignant tumors. Optimization of PDT requires investigation of the selectivity of PS for the target tissues, irradiating light source, irradiation wavelengths, fluence rate, fluence, illumination mode, and overall treatment plan. In this study, we developed the Multi-mode Automatized Well-plate PDT LED Laboratory Irradiation System (MAWPLIS), an innovative device that automates time-consuming well plate light dosage/PS dose measurement experiment. The careful control of LED current and temperature stabilization in the LED module allowed the system to achieve high optical output stability. The MAWPLIS was designed by integrating a 3-axis moving system and motion controller, a quick-switching LED controller unit equipped with interchangeable LED modules capable of employing multiple wavelengths, and a TEC system. The proposed system achieved high optical output stability (1 mW) within the range of 0-500 mW, high wavelength stability (5 nm) at 635 nm, and high temperature stability (0.2 °C) across all radiation modes. The system's validation involved in vitro analysis using 5-ALA across varying concentrations, incubation periods, light exposures, and wavelengths in HT-29 colon cancer and WI-38 human lung fibroblast cell lines. Specifically, a combination of 405 nm and 635 nm wavelengths was selected to demonstrate enhanced strategies for colon cancer cell eradication and system validation. The MAWPLIS system represents a significant advancement in photodynamic therapy (PDT) research, offering automation and standardization of time-intensive experiments, high stability and precision, and improved PDT efficacy through dual-wavelength integration.

Assessing cytotoxic activities, theoretical and in silico molecular docking calculations of phthalocyanines bearing cinnamyloxy-groups.

Cancer has been recognized as one of the deadliest diseases in the world in recent years. By chemically tailoring specific properties, anticancer agents can be prepared very effectively for the treatment of various cancer types. In this manner, as anticancer agents, a series of soluble metal-free and metallophthalocyanines carrying cinnamyloxy-groups at peripheral ß-positions have been prepared. All synthesized phthalocyanines were characterized by various spectroscopic approaches such as ultraviolet - visible (UV - Vis), Fourier transform infrared (FT-IR), and matrix-assisted laser deionization/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) techniques. These compounds are highly soluble in dimethyl sulfoxide (DMSO) and soluble in common organic solvents. The spectroscopic properties, cytotoxicity, and theoretical calculations of these complexes have been investigated. In cytotoxicity tests, compounds 1, 4, and 7 are the most active against HT-29 cell lines with IC50 values of 36.9 µM, 32.5 µM, and 51.1 µM, respectively. Also, the most and the least cytotoxic compounds against healthy CCD cell line is compounds 5 and 6 with the IC50 value of 13.4 µM and >250 µM, respectively. The PDB ID:4BQG target protein representing the HT-29 cancer cell line and the anti-cancer activities of phthalonitrile and its phthalocyanines were supported by molecular docking studies. Density Functional Theory (DFT) study supported the experimental results, including the spectral data, and implied that the compounds 5-7 are comparable by their characteristics, such as electronic properties, optical properties, electrostatic potentials, reactivity parameters, with the earlier studied compounds 2-4, which were successfully proved to be good candidates for cancer treatment.Communicated by Ramaswamy H. Sarma.

Complex bio rhythms.

Complex biorhythms are characteristic of ubiquitous phenomena appearing in many disciplines of human knowledge. This Special Issue collects articles devoted to different complex biorhythms phenomena such as cardiac dynamics, Covid-19 dynamics, dynamics of neural networks, cell dynamics, and a few articles devoted to general methods. It furnishes a rich overview of the field and can stimulate and inspire further researches.

Investigation of the therapeutic effect of 5-aminolevulinic acid based photodynamic therapy on hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a heterogeneous type of cancer and current treatment options limit successful therapy outcomes. Photodynamic therapy (PDT) has attracted attention as an alternative approach in the treatment of different types of cancer. However, there is no study in the literature regarding the effect of PDT on HCC, in vitro. Therefore, the aim of this study was to determine the cytotoxic and apoptotic effects of 5-aminolevulinic acid (5-ALA)/PDT on two different HCC cell lines in terms of hepatitis B virus (HBV) infection. The therapeutic effects of 5-ALA-based PDT on HCC cell lines (Huh-7 and SNU-449) were evaluated by PpIX-fluorescence accumulation, WST-1 analysis, Annexin V analysis, and acridine orange/ethidium bromide staining after irradiation with different light doses through diode laser. The results showed that 1 mM 5-ALA displayed higher PpIX fluorescence in the SNU-449 cell line than the Huh-7 cell line after 4 h of incubation. After irradiation with different light doses (3, 6, 9, and 12 J/cm2), 5-ALA significantly reduced the proliferation of HCC cells and induced apoptotic cell death (p < 0.01). Furthermore, SNU-449 cells were more responsive to 5-ALA-based PDT than Huh-7 cells due to possibly its molecular features as well as viral HBV status. Our preliminary data obtained from this study may contribute to the development of 5-ALA/PDT-based treatment strategies in the treatment of HCC. However, this study could be improved by the elucidation of the molecular mechanisms of cell death induced by 5-ALA/PDT in HCC cells, the use of different photosensitizer, light sources, and in vivo experiments.

Investigation of LED-based photodynamic therapy efficiency on breast cancer cells.

Photodynamic therapy (PDT) is based on special light source, photosensitizer (PS), and in the presence of oxygen. Different light sources have been used for PDT applications. Recent studies have focused on LED light sources for PDT applications due to reducing the cost of laser-based PDT and providing easy access for research laboratory or clinic facilities. LED-mediated PDT applications have shown promising results for the treatment of different types of disease. However, few studies have determined the effects of LED-based PDT on cancer cells. For the first time, the aim of this study was to explore the therapeutic effects of 5-aminolevulinic acid (5-ALA)-mediated PDT after LED irradiation on two sub-types (a poorly aggressive MCF-7 and a highly aggressive MDA-MB-231) of breast cancer cell lines. The effectiveness of 5-ALA PDT treatment was evaluated by WST-1, annexin V, and acridine orange staining with different energy levels. The LED system was specially developed with optical power and wavelength stability techniques. The system consists of user interface and embedded LED controller with real-time optic power output calibration by photodiode feedback. Our results demonstrated that the cell viability of breast cancer cells was considerably decreased a LED dose-dependent manner (P < 0.05). Additionally, a significant increase in the percentage of apoptotic cells was detected in breast cancer cells after irradiation with LED at a density of 18 and 30 J/cm2 energy. Consequently, the LED system could be effectively used for irradiation of 5-ALA in the treatment of breast cancer cells.

The effect of attentional focusing strategies on EMG-based classification.

Earlier studies showed that external focusing enhances motor performance and reduces muscular activity compare to internal one. However, low activity is not always desired especially in case of Human-Machine Interface applications. This study is based on investigating the effects of attentional focusing preferences on EMG based control systems. For the EMG measurements via biceps brachii muscles, 35 subjects were asked to perform weight-lifting under control, external and internal focus conditions. The difference between external and internal focusing was found to be significant and internal focus enabled higher EMG activity. Besides, six statistical features, namely, RMS, maximum, minimum, mean, standard deviation, and variance were extracted from both time and frequency domains to be used as inputs for Artificial Neural Network classifiers. The results found to be 87.54% for ANN1 and 82.69% for ANN2, respectively. These findings showed that one's focus of attention would be predicted during the performance and unlike the literature, internal focusing could be also useful when it is used as an input for HMI studies. Therefore, attentional focusing might be an important strategy not only for performance improvement to human movement but also for advancing the study of EMG-based control mechanisms.

Diagnostic Methods, Clinical Guidelines, and Antibiotic Treatment for Group A Streptococcal Pharyngitis: A Narrative Review.

The most common bacterial cause of pharyngitis is infection by Group A ß-hemolytic streptococcus (GABHS), commonly known as strep throat. 5-15% of adults and 15-35% of children in the United States with pharyngitis have a GABHS infection. The symptoms of GABHS overlap with non-GABHS and viral causes of acute pharyngitis, complicating the problem of diagnosis. A careful physical examination and patient history is the starting point for diagnosing GABHS. After a physical examination and patient history is completed, five types of diagnostic methods can be used to ascertain the presence of a GABHS infection: clinical scoring systems, rapid antigen detection tests, throat culture, nucleic acid amplification tests, and machine learning and artificial intelligence. Clinical guidelines developed by professional associations can help medical professionals choose among available techniques to diagnose strep throat. However, guidelines for diagnosing GABHS created by the American and European professional associations vary significantly, and there is substantial evidence that most physicians do not follow any published guidelines. Treatment for GABHS using analgesics, antipyretics, and antibiotics seeks to provide symptom relief, shorten the duration of illness, prevent nonsuppurative and suppurative complications, and decrease the risk of contagion, while minimizing the unnecessary use of antibiotics. There is broad agreement that antibiotics with narrow spectrums of activity are appropriate for treating strep throat. But whether and when patients should be treated with antibiotics for GABHS remains a controversial question. There is no clearly superior management strategy for strep throat, as significant controversy exists regarding the best methods to diagnose GABHS and under what conditions antibiotics should be prescribed.

A Nationwide Study of Intimate Partner Violence.

BACKGROUND: Intimate partner violence (IPV) refers to physical or sexual violence, stalking, and psychological aggression by an intimate partner. The present study aims to examine the incidence, injury patterns, and outcomes using a representative nationwide data set. STUDY DESIGN: The Nationwide Emergency Department Sample database was queried from 2010 to 2014 to identify IPV in adult patients by injury code E967.3. Demographics, diagnoses, and injury mechanisms were captured. Primary outcome was mortality, and logistic regression analyses were used to compare the baselines and outcomes. RESULTS: 132 806 IPV emergency visits were identified, with 5.1% of patients requiring hospitalization. Most patients were female (92.6%). The most common injury mechanisms were unintentional injury (36%) and striking (22.0%). Contusions of face/scalp/neck (13.2%) and unspecified head injury (6.9%) were the most common diagnoses. Males were significantly older [median and interquartile range of 39 (30, 50)] than females [33 (26, 43)], and were more frequently hospitalized (6.7% vs. 5.0%, P = .002) with more injuries with injury severity score ≥ 15 (.7% vs. .4%, P = .004) than females. Overall, IPV-related mortality was .06%, .26% in males and .05% in females (P = .003). Older age (odds ratio (OR) = 1.053) and male gender (OR = 3.102) were significantly associated with mortality. The annual incidence rate decreased from 9.7 in 2010 to 8.2/100 000 US population in 2014 (R2 = .659). CONCLUSIONS: Young women are more likely to be victims of IPV, whereas men are more likely to be older and hospitalized with more severe injuries and worse outcomes.

Development of new descriptor for melanoma detection on dermoscopic images.

Early detection of melanoma has critical importance for the success of the treatment. However, a successful early diagnosis is only possible with the existence of discriminative features. In this study, a new descriptor based on the number of colors was developed in order to successfully diagnose lesions of melanoma. The number of colors is the main feature in the identification of melanoma-type skin lesions. The user must select a threshold value when calculating the number of colors of the lesion. The incorrect threshold value selection of non-expert users disrupts the aforementioned feature and also leads to significant diagnostic errors. In this study, it was revealed that color counting threshold values have a significant effect on the distinctiveness of the number of colors. In the three dermoscopic databases, color counting threshold values that provide the maximum distinctiveness on melanoma and benign lesions were determined as 0 and 0.123 respectively. By using these color counting threshold values, the number of colors for each sample in the data sets was calculated separately. Following that, a novel attribute called the number of color difference was defined as a function of color counting threshold values. Experiments using only the proposed new descriptor yielded 52.7% higher f-measure and 84.5% higher true-positive performance than the number of colors used in the literature. The results obtained in this study revealed the importance of accurately determining the number of colors the lesions had and states that the applied color counting threshold significantly influences the classification results. Thereby, a new method is proposed for determining the critical color counting threshold. We claim that the classical ABCD rule should be improved by our new descriptor. Graphical abstract Fig. 1 Selection of threshold has vital effect on skin lesion classification. A new method to select the correct threshold value and a new attribute for correct classification were developed.

Generation of highly selective monoclonal antibodies inhibiting a recalcitrant protease using decoy designs.

Matrix metalloproteinase-12 (MMP-12), also known as macrophage elastase, is a potent inflammatory mediator and therefore an important pharmacological target. Clinical trial failures of broad-spectrum compound MMP inhibitors suggested that specificity is the key for a successful therapy. To provide the required selectivity, monoclonal antibody (mAb)-based inhibitors are on the rise. However, poor production of active recombinant human MMP-12 catalytic domain (cdMMP-12) presented a technical hurdle for its inhibitory mAb development. We hypothesized that this problem could be solved by designing an expression-optimized cdMMP-12 mutant without structural disruptions at its reaction cleft and surrounding area, and thus isolated active-site inhibitory mAbs could maintain their binding and inhibition functions toward wild-type MMP-12. We combined three advances in the field-PROSS algorithm for cdMMP-12 mutant design, convex paratope antibody library construction, and functional selection for inhibitory mAbs. As a result, isolated Fab inhibitors showed nanomolar affinity and potency toward cdMMP-12 with high selectivity and high proteolytic stability. Particularly, Fab LH11 targeted the reaction cleft of wild-type cdMMP-12 with 75 nM binding KD and 23 nM inhibition IC50 . We expect that our methods can promote the development of mAbs inhibiting important proteases, many of which are recalcitrant to functional production.

What Do We Need to Know to Improve Diagnostic Testing Methods for the 2019 Novel Coronavirus?

There is widespread agreement that reliable, fast, and easy-to-produce diagnostic testing methods that have high sensitivity and specificity are essential for guiding appropriate responses to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak. At the present time, there are important unanswered questions about testing methods for SARS-CoV-2. This review article interprets recent findings related to the principal testing methods used to diagnose SARS-CoV-2, including reverse-transcription polymerase chain reaction (RT-PCR), chest imaging, and immunoassay. We discuss the value and limitations of these approaches and suggest directions for future research that can advance the understanding of diagnostic methods. Addressing areas of uncertainty will improve clinical outcomes and allow more effective policies to be implemented to control the disease.

Optimization of 5-aminolevulinic acid-based photodynamic therapy protocol for breast cancer cells.

BACKGROUND: Photodynamic therapy (PDT) is a therapeutic strategy for the treatment of cancer. 5-aminolevulinic acid (5-ALA) as a precursor of the protoporphyrin IX (PpIX) has a great potential for PDT application. Although 5-ALA-based PDT has been studied in many pre-clinical and clinical studies for breast cancer, there are different PDT application protocols in the literature. Therefore, the aim of this study was to determine the optimal in vitro protocol for 5-ALA-based PDT in breast cancer treatment. METHODS: The therapeutic effects of 5-ALA (1 and 2.5 mM) on two different subtypes of breast cancer cell line (MCF-7 and MDA-MB-231) were evaluated by PpIX-fluorescence accumulation and WST-1 analysis. Then, the cells were irradiated with diode laser at different doses (1.5, 3, 6, 9 and 12 J/cm2). After irradiation, the anticancer effects of 5-ALA were analyzed through cell viability and cell death analysis. RESULTS: Our results showed that 5-ALA exhibited a higher PpIX fluorescence in both breast cancer cells for 4 h incubation. After irradiation, 1 mM 5-ALA significantly reduced the proliferation of breast cancer cells in a laser dose-dependent manner and induced apoptotic cell death upon 24 h incubation (p < 0.05). However, MDA-MB-231 cells were more sensitive to 5-ALA-based PDT than MCF-7 cells in a dose of 9 J/cm2 and 12 J/cm2. CONCLUSION: Our preliminary findings proposed an optimal in vitro protocol of 5-ALA-based PDT by using a laser diode for breast cancer. However, there is a need to investigate the underlying molecular mechanisms of 5-ALA/PDT sensitivity among the subtypes of breast cancer.

A New handheld singlet oxygen detection system (SODS) and NIR light source based phantom environment for photodynamic therapy applications.

Photodynamic therapy (PDT) is an emerging treatment modality in various areas such as cancer treatment and disinfection. The photosensitizer and oxygen have crucial roles for effective PDT treatment. The quantitative evaluation of singlet oxygen, which is a gold standard for monitoring effective treatment, remains as an important problem for PDT. However, low quantum yield and low life span of the singlet oxygen make the system expensive, unnecessarily large and unadaptable for clinical usage. In our study, a new mobile singlet oxygen detection system (SODS) was designed to detect singlet oxygen illumination during PDT and a new singlet oxygen phantom environment was constituted to test the designed SODS system. The singlet oxygen phantom environment composed of fast switching led driver & microcontroller and led light source (1200-1300 nm radiation). The elements of the singlet oxygen detection system are optic filter and collimation, avalanche photodiode transimpedance amplifier, differential amplifier and a signal processing block. According to the performance evaluation of the system on the phantom environment, the presented SODS can measure the illuminations at 1270 nm wavelength between 10 ns and 15 µs timespans. The results showed that the proposed system might be a good candidate for clinical PDT applications.

Functional selection of protease inhibitory antibodies.

Critical for diverse biological processes, proteases represent one of the largest families of pharmaceutical targets. To inhibit pathogenic proteases with desired selectivity, monoclonal antibodies (mAbs) hold great promise as research tools and therapeutic agents. However, identification of mAbs with inhibitory functions is challenging because current antibody discovery methods rely on binding rather than inhibition. This study developed a highly efficient selection method for protease inhibitory mAbs by coexpressing 3 recombinant proteins in the periplasmic space of Escherichia coli-an antibody clone, a protease of interest, and a ß-lactamase modified by insertion of a protease cleavable peptide sequence. During functional selection, inhibitory antibodies prevent the protease from cleaving the modified ß-lactamase, thereby allowing the cell to survive in the presence of ampicillin. Using this method to select from synthetic human antibody libraries, we isolated panels of mAbs inhibiting 5 targets of 4 main protease classes: matrix metalloproteinases (MMP-14, a predominant target in metastasis; MMP-9, in neuropathic pain), ß-secretase 1 (BACE-1, an aspartic protease in Alzheimer's disease), cathepsin B (a cysteine protease in cancer), and Alp2 (a serine protease in aspergillosis). Notably, 37 of 41 identified binders were inhibitory. Isolated mAb inhibitors exhibited nanomolar potency, exclusive selectivity, excellent proteolytic stability, and desired biological functions. Particularly, anti-Alp2 Fab A4A1 had a binding affinity of 11 nM and inhibition potency of 14 nM, anti-BACE1 IgG B2B2 reduced amyloid beta (Aß40) production by 80% in cellular assays, and IgG L13 inhibited MMP-9 but not MMP-2/-12/-14 and significantly relieved neuropathic pain development in mice.

Selectivity Conversion of Protease Inhibitory Antibodies.

Background: Proteases are one of the largest pharmaceutical targets for drug developments. Their dysregulations result in a wide variety of diseases. Because proteolytic networks usually consist of protease family members that share high structural and catalytic homology, distinguishing them using small molecule inhibitors is often challenging. To achieve specific inhibition, this study described a novel approach for the generation of protease inhibitory antibodies. As a proof of concept, we aimed to convert a matrix metalloproteinase (MMP)-14 specific inhibitor to MMP-9 specific inhibitory antibodies with high selectivity. Methods: An error-prone single-chain Fv (scFv) library of an MMP-14 inhibitor 3A2 was generated for yeast surface display. A dual-color competitive FACS was developed for selection on MMP-9 catalytic domain (cdMMP-9) and counter-selection on cdMMP-14 simultaneously, which were fused/conjugated with different fluorophores. Isolated MMP-9 inhibitory scFvs were biochemically characterized by inhibition assays on MMP-2/-9/-12/-14, proteolytic stability tests, inhibition mode determination, competitive ELISA with TIMP-2 (a native inhibitor of MMPs), and paratope mutagenesis assays. Results: We converted an MMP-14 specific inhibitor 3A2 into a panel of MMP-9 specific inhibitory antibodies with dramatic selectivity shifts of 690-4,500 folds. Isolated scFvs inhibited cdMMP-9 at nM potency with high selectivity over MMP-2/-12/-14 and exhibited decent proteolytic stability. Biochemical characterizations revealed that these scFvs were competitive inhibitors binding to cdMMP-9 near its reaction cleft via their CDR-H3s. Conclusions: This study developed a novel approach able to convert the selectivity of inhibitory antibodies among closely related protease family members. This methodology can be directly applied for mAbs inhibiting many proteases of biomedical importance.

Epitope-specific affinity maturation improved stability of potent protease inhibitory antibodies.

Targeting effectual epitopes is essential for therapeutic antibodies to accomplish their desired biological functions. This study developed a competitive dual color fluorescence-activated cell sorting (FACS) to maturate a matrix metalloprotease 14 (MMP-14) inhibitory antibody. Epitope-specific screening was achieved by selection on MMP-14 during competition with N-terminal domain of tissue inhibitor of metalloproteinase-2 (TIMP-2) (nTIMP-2), a native inhibitor of MMP-14 binding strongly to its catalytic cleft. 3A2 variants with high potency, selectivity, and improved affinity and proteolytic stability were isolated from a random mutagenesis library. Binding kinetics indicated that the affinity improvements were mainly from slower dissociation rates. In vitro degradation tests suggested the isolated variants had half lives 6-11-fold longer than the wt. Inhibition kinetics suggested they were competitive inhibitors which showed excellent selectivity toward MMP-14 over highly homologous MMP-9. Alanine scanning revealed that they bound to the vicinity of MMP-14 catalytic cleft especially residues F204 and F260, suggesting that the desired epitope was maintained during maturation. When converted to immunoglobulin G, B3 showed 5.0 nM binding affinity and 6.5 nM inhibition potency with in vivo half-life of 4.6 days in mice. In addition to protease inhibitory antibodies, the competitive FACS described here can be applied for discovery and engineering biosimilars, and in general for other circumstances where epitope-specific modulation is needed.

Identification of highly selective MMP-14 inhibitory Fabs by deep sequencing.

Matrix metalloproteinase (MMP)-14 is an important target for cancer treatment due to its critical roles in tumor invasion and metastasis. Previous failures of all compound-based broad-spectrum MMP inhibitors in clinical trials suggest that selectivity is the key for a successful therapy. With inherent high specificity, monoclonal antibodies (mAbs) therefore arise as attractive inhibitors able to target the particular MMP of interest. As a routine screening method, enzyme-linked immunosorbent assays (ELISA) have been applied to panned phage libraries for the isolation of mAbs inhibiting MMP-14. However, because of suboptimal growth conditions and insufficient antibody expression associated with monoclonal ELISA, a considerable number of potentially inhibitory clones might not be identified. Taking advantage of next-generation sequencing (NGS), we monitored enrichment profiles of millions of antibody clones along three rounds of phage panning, and identified 20 Fab inhibitors of MMP-14 with inhibition IC50 values of 10-4,000 nM. Among these inhibitory Fabs, 15 were not found by monoclonal phage ELISA. Particularly, Fab R2C7 exhibited an inhibition potency of 100 nM with an excellent selectivity to MMP-14 over MMP-9. Inhibition kinetics and epitope mapping suggested that as a competitive inhibitor, R2C7 directly bound to the vicinity of the MMP-14 catalytic site. This study demonstrates that deep sequencing is a powerful tool to facilitate the systematic discovery of mAbs with protease inhibition functions. Biotechnol. Bioeng. 2017;114: 1140-1150. © 2017 Wiley Periodicals, Inc.

Relationship between vibrotactile detection threshold in the Pacinian channel and complex mechanical modulus of the human glabrous skin.

The goal of this study was to investigate the relationship between the psychophysical vibrotactile thresholds of the Pacinian (P) channel and the mechanical properties of the skin at the fingertip. Seven healthy adult subjects (age: 23-30) participated in the study. The mechanical stimuli were 250-Hz sinusoidal bursts and applied with cylindrical contactor probes of radii 1, 2, and 3.5 mm on three locations at the fingertip. The duration of each burst was 0.5 s (rise and fall time: 50 ms). The subjects performed a two-interval forced-choice task while the stimulus levels changed for tracking the threshold at 75% probability of detection. There were significant main effects of contactor radius and location (two-way ANOVA, values of p < 0.001). The thresholds decreased as the contactor radius increased (i.e., spatial summation effect) at all locations. The thresholds were lowest near the whorl at the fingertip. Additionally, we measured the mechanical impedance (specifically, the storage and loss moduli) at the contact locations. The storage moduli did not change with the contactor location, but the loss moduli were lowest near the whorl. While the loss moduli decreased, the storage moduli increased (e.g., more springiness) as the contactor radius increased. There was moderate and barely significant correlation between the absolute thresholds and the storage moduli (r = 0.650, p = 0.058). However, the correlation between the absolute thresholds and the loss moduli was high and very significant (r = 0.951, p < 0.001). The results suggest that skin mechanics may be important for locally shaping psychophysical detection thresholds, which would otherwise be expected to be constant due to uniform Pacinian innervention density at the fingertip.

An optoelectromechanical tactile sensor for detection of breast lumps.

We developed a compact tactile imaging (TI) system to guide the clinician or the self-user for noninvasive detection of breast tumors. Our system measures the force distribution based on the difference in stiffness between a palpated object and an abnormality within. The average force resolution, force range, and the spatial resolution of the device are 0.02 N, 0-4 N, and 2.8 mm, respectively. To evaluate the performance of the proposed TI system, compression experiments were performed to measure the sensitivity and specificity of the system in detecting tumor-like inclusions embedded in tissue-like cylindrical silicon samples. Based on the experiments performed with 11 inclusions, having two different sizes and two different stiffnesses located at three different depths, our TI system showed an average sensitivity of 90.8 ± 8.1 percent and an average specificity of 89.8 ± 12.7 percent. Finally, manual palpation experiments were performed with 12 human subjects on the same silicon samples and the results were compared to that of the TI system. The performance of the TI system was significantly better than that of the human subjects in detecting deep inclusions while the human subjects performed slightly better in detecting shallow inclusions close to the contact surface.