Saline dry fixation for improved cell composition analysis using Raman spectroscopy.

Raman spectroscopy enables the label-free assessment of cellular composition. While live cell analysis is the most accurate approach for cellular Raman spectroscopy, the analysis of fixed cells has proved to be very useful, particularly in collaborative projects where samples need to be serially examined by different laboratories or stored and reanalyzed at a later date. However, many chemicals that are widely used for cell fixation directly affect cellular biomolecules, yielding Raman spectra with missing or altered information. In this article, we compared the suitability of dry-fixation with saline versus chemical fixatives. We compared the Raman spectroscopy of saline dry-fixed cells with the more commonly used formaldehyde and methanol fixation and found that dry-fixed cell spectra preserved more cellular information than either chemical fixative. We also assessed the stability of dry-fixed cells over time and found that they were stable for at least 5 months. Finally, a comparison of dry-fixed and live cell spectra revealed effects due to the hydration state of the cells since they were recovered upon rehydrating dry-fixed samples. Thus, for fixed cell Raman spectroscopy, we recommend dry-fixation with unbuffered saline as a superior method to formaldehyde or methanol fixation.

Expression of Hedgehog signalling molecules in microcystic adnexal carcinoma.

BACKGROUND: Microcystic adnexal carcinoma (MAC) is a rare skin neoplasm that has not been characterized on a molecular basis. AIM: To assess expression profiles of Hedgehog (HH) signalling molecules in MAC and control tumours. METHODS: Immunohistochemistry was performed for Sonic Hedgehog (SHH), Indian Hedgehog (IHH), Patched 1 (PTCH1) and Smoothened (SMO) on patient MAC tissue (n = 26) and control tumour tissue, including syringoma (SyG; n = 11), trichoepithelioma (TE; n = 11) and basal cell carcinoma (BCC; n = 12) tissues. RESULTS: Patched 1 and SMO immunoreactivity was significantly higher in BCC than in SyG, TE or MAC (P < 0.001 and P < 0.03, respectively). The highest IHH expression was observed in BCC and TE compared with SyG and MAC (P < 0.04). Notably, the highest SHH protein expression was observed in SyG compared with MAC, TE and even BCC (P < 0.001). In patients with MAC, SMO immunoreactivity significantly (r = 0.51; P < 0.01) correlated with PTCH1 expression. Further correlation studies did not show significant associations between the HH expression markers assessed (P > 0.05). CONCLUSION: Our results indicate that alterations of the HH signalling are unlikely to play a major role in the pathogenesis of MAC, which is in contrast to the morphologically similar BCC and TE. Our observation provides additional information to the limited molecular pathology knowledge on this rare tumour.

Effectiveness, safety and utilization of vismodegib in locally advanced basal cell carcinoma under real-world conditions in Germany - The non-interventional study NIELS.

BACKGROUND: Basal cell carcinoma (BCC) can arise by the uncontrolled proliferation of cells from multiple epidermal compartments due to aberrant activation of the Hedgehog (Hh) signalling pathway. Vismodegib, a small-molecule inhibitor of this pathway, is approved for treatment of patients with locally advanced (la) BCC inappropriate for surgery or radiotherapy or patients with symptomatic metastatic (m) BCC. OBJECTIVES: The aim of this non-interventional study was to assess effectiveness with a special focus on duration of response (DOR), safety and utilization of vismodegib for treatment of laBCC in daily practice in Germany. METHODS: This non-interventional study (NIS) observed treatment of laBCC with vismodegib according to the German label in clinical practice. All available patients who had received at least one dose of vismodegib between commercial availability of vismodegib in Germany (02 August 2013) and 3 years before end of study (31 March 2016) could be included and were documented retrospectively and/or prospectively for up to 3 years. Primary effectiveness variable was DOR. Assessment of tumour response was carried out by the treating physicians. Exploratory variables included utilization of vismodegib, decision makers for therapy and method of tumour response evaluation. All statistical analyses were descriptive. RESULTS: Between September 2015 and March 2019, 66 patients were observed at 26 German centres. The objective response rate (ORR) was 74.2% and the disease control rate (DCR) was 90.9%. The median DOR was 15.9 months (95% CI: 9.2; 25.7; n = 49 patients with response). The median progression-free survival (PFS) was 19.1 months and the median time to response (TTR) 2.7 months. A total of 340 adverse events were reported in 63 (95.5%) patients; no new safety signals were identified. CONCLUSIONS: The NIS NIELS shows effectiveness and safety of vismodegib in patients with laBCC. It confirms the transferability of the results of the pivotal trial into routine clinical practice.

[Reducing tinnitus intensity : Pilot study to attenuate tonal tinnitus using individually spectrally optimized near-threshold noise]. / Reduktion der Tinnituslautstärke : Pilotstudie zur Abschwächung von tonalem Tinnitus mit schwellennahem, individuell spektral optimiertem Rauschen.

BACKGROUND: Around 15% of the general population is affected by tinnitus, but no real cure exists despite intensive research. Based on our recent causal model for tinnitus development, we here test a new treatment aimed at counteracting the perception. This treatment is based on the stochastic resonance phenomenon at specific auditory system synapses that is induced by externally presented near-threshold noise. OBJECTIVE: This pilot study will investigate whether individually spectrally adapted noise can successfully reduce chronic tonal/narrow-band tinnitus during stimulation. MATERIALS AND METHODS: Hearing loss (HL) as well as tinnitus pitch (TP) and loudness (TL) were audiometrically measured in 22 adults (46.6±16.3 years; 4 women) with tinnitus. Based on these measurements, up to eight different noise stimuli with five intensities (-20 to +20 dB SL) were generated. These were presented for 40 s each via audiologic headphones in a soundproof chamber. After each presentation, the change in TL was rated on a five-level scale (-2 to +2). RESULTS: We found patients (n = 6) without any improvement in their TL perception as well as patients with improvement (n = 16), where stimulation around the TP was most effective. The groups differed in post-hoc analysis of their audiograms: the effectiveness of our new therapeutic strategy obviously depends on the individual HL, and was most effective in normal-hearing tinnitus patients and those with mild HL. CONCLUSION: Subjective TL could be reduced in 16 out of 22 patients during stimulation. For a possible success of a future therapy, the HL seems to be of relevance.

Long-term efficacy and safety of sonidegib in patients with advanced basal cell carcinoma: 42-month analysis of the phase II randomized, double-blind BOLT study.

BACKGROUND: Basal cell carcinomas (BCCs) exhibit aberrant activation of the hedgehog pathway. Sonidegib is a hedgehog pathway inhibitor approved for the treatment of locally advanced BCC (laBCC) and metastatic BCC (mBCC) based on primary results of the BOLT study [Basal Cell Carcinoma Outcomes with LDE225 (sonidegib) Treatment]. OBJECTIVES: This is the final 42-month analysis of the BOLT study, evaluating the efficacy and safety of sonidegib. METHODS: Adults with no prior hedgehog pathway inhibitor therapy were randomized in a 1 : 2 ratio to sonidegib 200 mg or 800 mg once daily. Treatment continued for up to 42 months or until disease progression, unacceptable toxicity, death, study termination or withdrawal of consent. The primary efficacy end point was the objective response rate (ORR) by central review, assessed at baseline; weeks 5, 9 and 17; then subsequently every 8 or 12 weeks during years 1 or 2, respectively. Safety end points included adverse event monitoring and reporting. RESULTS: The study enrolled 230 patients, 79 and 151 in the 200-mg and 800-mg groups, respectively, of whom 8% and 3.3% remained on treatment by the 42-month cutoff, respectively. The ORRs by central review were 56% [95% confidence interval (CI) 43-68] for laBCC and 8% (95% CI 0·2-36) for mBCC in the 200-mg group and 46·1% (95% CI 37·2-55·1) for laBCC and 17% (95% CI 5-39) for mBCC in the 800-mg group. No new safety concerns emerged. CONCLUSIONS: Sonidegib demonstrated sustained efficacy and a manageable safety profile. The final BOLT results support sonidegib as a viable treatment option for laBCC and mBCC. What's already known about this topic? Basal cell carcinoma (BCC) is usually treatable with surgery or radiation therapy, but there are limited treatment options for patients with advanced BCC. Sonidegib, a hedgehog pathway inhibitor approved for the treatment of advanced BCC, demonstrated clinically relevant efficacy and manageable safety in prior analyses of the phase II randomized, double-blind BOLT study [Basal Cell Carcinoma Outcomes with LDE225 (sonidegib) Treatment]. What does this study add? This final 42-month analysis of BOLT is the longest follow-up available for a hedgehog pathway inhibitor. Clinically relevant efficacy results were sustained from prior analyses, with objective response rates by central review of the approved 200-mg daily dose of 56% in locally advanced BCC and 8% in metastatic BCC. No new safety concerns were raised. The results confirmed sonidegib as a viable long-term treatment option for patients with advanced BCC.

Applications of Raman spectroscopy in the development of cell therapies: state of the art and future perspectives.

Therapies based on injecting living cells into patients offer a huge potential to cure many degenerative and deadly diseases, with hundreds of clinical trials ongoing. Due to their complex nature, a basic understanding of their biochemical and functional characteristics, how to manufacture them for safe and efficacious therapy, and how to effectively implement them in clinical settings are very challenging. Raman spectroscopy could provide an information-rich, non-invasive, non-destructive analytical method to complement the use of conventional sample-based, infrequent and destructive biochemical assays typically employed to analyze and validate the quality of therapeutic cells. This article provides an overview of the current state of emerging cell therapies, and then reviews the related Raman spectroscopic state of the art analysis of human cells. This includes spectroscopic data processing considerations, the scope offered by technical variants of Raman spectroscopy, and analytical difficulties encountered by spectroscopists working with therapeutic cells. Finally, we outline a number of salient challenges as cell therapy products are translated from the laboratory to the clinic, and propose how Raman spectroscopy-based solutions could address these challenges.

Correction: Applications of Raman spectroscopy in the development of cell therapies: state of the art and future perspectives.

Correction for 'Applications of Raman spectroscopy in the development of cell therapies: state of the art and future perspectives' by Shreyas Rangan et al., Analyst, 2020, DOI: 10.1039/c9an01811e.

Lysyl oxidase-like-2 mutations and reduced mRNA and protein expression in mid-dermal elastolysis.

BACKGROUND: Mid-dermal elastolysis (MDE) is a rare skin condition, characterized by selective loss of elastic fibres in the mid dermis. The pathogenesis of MDE is still unclear. AIM: To investigate expression of lysyl oxidase-like 2 (LOXL2) in a reasonable sample of patients with MDE and to search for mutations in LOXL2. METHODS: We investigated archived lesional tissue of 13 patients with MDE and skin tissue samples of 10 sex- and age-matched healthy controls (HCs). Gene and protein expression of LOXL2 was investigated using real-time reverse-transcription PCR and immunohistochemistry. Mutation analysis was performed using the Sanger method. RESULTS: We observed decreased LOXL2 mRNA expression in lesional skin of patients with MDE (0.48 ± 0.16) compared with healthy skin of the same patients (1.5 ± 0.51) and normal skin of HCs (1.9 ± 0.13). Compared with healthy patient skin (epidermis 2.38 ± 1.6, dermis 1.2 ± 1), LOXL2 protein expression in lesional patient skin (epidermis 1.1 ± 0.7, dermis 0.3 ± 0.45) was significantly decreased (P < 0.04 and P = 0.02, respectively). Mutation analysis of the entire LOXL2 gene could be performed for five patients, all of whom were found to have at least one mutation in the LOXL2 gene. Three of these had a mutation in the promoter region (c.967 G>C, c.1022 C>T, and c.1025 G>A, respectively), and one of them also had a mutation in the splice region of intron 11/exon 12 (IVS11-1 G>A). Of the remaining two patients, one had a mutation in exon 3 (T1391), and the other had a mutation in exon 11 (C663Y). CONCLUSIONS: Our present data suggest that decreased elastin renewal due to LOXL2 mutations and consecutive reduced LOXL2 expression contribute to the pathogenesis of MDE.

[Models of tinnitus development : From cochlea to cortex]. / Modelle der Tinnitusentstehung : Von der Cochlea zum Kortex.

The development of subjective tinnitus is still not mechanistically understood and existing models are controversially discussed. In this overview, the authors discuss three of the main models, all of which propose damage to the cochlea as the initial step in tinnitus development. Based on these models, a possible manifestation of tinnitus-related neuronal activity at the perceptually relevant level of the auditory pathway, the auditory cortex, is presented. Furthermore, it is demonstrated that one of the models offers a new view on the phenomenon, which could potentially help patients to better cope with their condition.

Is ultraviolet exposure acquired at work the most important risk factor for cutaneous squamous cell carcinoma? Results of the population-based case-control study FB-181.

BACKGROUND: Squamous cell carcinoma (SCC) is one of the most frequent types of cancer constituting a significant public health burden. Prevention strategies focus on limiting ultraviolet (UV) exposure during leisure time. However, the relative impact of occupational and nonoccupational UV exposure for SCC occurrence is unclear. OBJECTIVES: To investigate the association between occupational and nonoccupational UV exposure for SCC in a multicentre population-based case-control study hypothesizing that high occupational UV exposure increases the risk of SCC. METHODS: Consecutive patients with incident SCC (n = 632) were recruited from a German national dermatology network. Population-based controls (n = 996) without history of skin cancer were recruited from corresponding residents' registration offices and propensity score matched to cases. Lifetime UV exposure, sociodemographic and clinical characteristics were assessed by trained physicians. Occupational and nonoccupational UV exposure doses were estimated by masked investigators using established reference values. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were assessed using conditional logistic regression adjusting for relevant confounders. RESULTS: Total solar UV exposure was significantly associated with increased SCC. The OR for high (> 90th percentile) vs. low (< 40th percentile) and high vs, moderate (40-59th percentile) occupational UV exposure was 1·95 (95% CI 1·19-3·18) and 2·44 (95% CI 1·47-4·06) for SCC. Adjusting for occupational UV exposure, nonoccupational UV exposure was not significantly related to SCC incidence. Dose-response relationships were observed for occupational but not for nonoccupational solar UV exposure. CONCLUSIONS: Solar occupational UV exposure is a major determinant of incident SCC. Our findings indicate that prevention strategies should be further expanded to the occupational setting.

A randomized, multinational, noninferiority, phase III trial to evaluate the safety and efficacy of BF-200 aminolaevulinic acid gel vs. methyl aminolaevulinate cream in the treatment of nonaggressive basal cell carcinoma with photodynamic therapy.

BACKGROUND: Basal cell carcinoma (BCC) represents the most common nonmelanoma skin cancer worldwide, affecting mainly adult, fair-skinned individuals. The World Health Organization distinguishes aggressive and nonaggressive forms, of which prototypical variants of the latter are primary nodular and superficial BCC. OBJECTIVES: To demonstrate noninferiority of BF-200 ALA (a nanoemulsion gel containing 5-aminolaevulinic acid) compared with MAL (a cream containing methyl aminolaevulinate) in the treatment of nonaggressive BCC with photodynamic therapy (PDT). Noninferiority of the primary efficacy variable (overall patient complete response 12 weeks after last PDT) would be declared if the mean response for BF-200 ALA was no worse than that for MAL, within a statistical margin of Δ = -15%. METHODS: The study was a randomized, phase III trial performed in Germany and the U.K. with ongoing 5-year follow-up. Of 281 randomized patients, 138 were treated with BF-200 ALA and 143 with MAL. Patients received two PDT sessions 1 week apart. Remaining lesions 12 weeks after the second PDT were retreated. Illumination was performed with a red light source (635 nm, 37 J cm-2 ). The results shown include clinical end points and patients' reassessment 12 months after the last PDT. The study was registered with EudraCT (number 2013-003241-42). RESULTS: Of the BF-200 ALA-treated patients, 93·4% were complete responders compared with 91·8% in the MAL group. The difference of means was 1·6, with a one-sided 97·5% confidence interval of -6·5, establishing noninferiority (P < 0·0001). The results for secondary efficacy parameters were in line with the primary outcome. Recurrence rates 12 months after the last treatment were ≤ 10%. CONCLUSIONS: Treatment of nonaggressive BCC with BF-200 ALA-PDT is highly effective and well tolerated with proven noninferiority to MAL-PDT. It demonstrates low recurrence rates after 1 year of follow-up.

Raman spectroscopy of stored red blood cell concentrate within sealed transfusion blood bags.

The standard practice in blood banks worldwide involves storage of red blood cells (RBCs) in plastic bags until they are needed for transfusion. During storage, the cells gradually degrade in functionality, a condition described as RBC storage lesion. Standard analytical techniques cannot assess the blood quality without breaching the sterility of the transfusion bag. In this study, we employed a commercially available spatially offset Raman spectroscopy (SORS) system using a custom designed protocol to non-invasively explore the biochemical changes in RBC concentrate of healthy donors over a storage period of approximately 42 days in standard transfusion bags, under standard storage conditions. The results reveal an increase in the oxygenation state of haemoglobin over the storage period for all donors, but different profiles for each donor. This study demonstrates the feasibility of acquiring consistent biochemical information relevant to the quality of stored blood, in situ through sealed blood transfusion bags using a commercially available instrument.

Deposits in the lungs of Kwäday Dän Ts'ìnchi man: Characterization by a combination of analytical microscopical methods.

OBJECTIVES: The approximately 250 years old remains of the Kwäday Dän Ts'ìnchi man were found in a glacier in Canada. Studying the state of preservation of the corpse, we observed black deposits in his lung. Following this observation we wanted to determine: (1) location of the deposits in the lung tissue, (2) composition and origins of the deposits. METHODS: By light microscopy (LM) and transmission electron microscopy (TEM), we studied the deposits in the Kwäday Dän Ts'ìnchi man' s lung and compared it with distribution of anthracotic deposits in contemporary samples from the David Harwick Pathology Centre (DHPC). To determine chemical composition of the inclusions we used Raman spectroscopy. Scanning electron microscopy and elemental mapping was used for determine the chemical elements. RESULTS: The histopathological identification of anthracosis in the Kwäday Dän Ts'ìnchi man's lung allowed us to distinguish crushed parenchyma from conducting airway tissue and identification of particles using LM and TEM. Crystal particles were found using TEM. Ordered carbonaceous material (graphene and graphite), disordered carbonaceous material (soot) and what might be minerals (likely conglomerates) were found with Raman spectrometry. Gold and lead particles in the lung were discovered with scanning electron microscopy and elemental mapping. CONCLUSIONS: Presence of soot particles in anthracotic areas in the Kwäday Dän Ts'ìnchi man's lung probably were due to an inhalation of particles in open fires. Gold and lead particles are most likely of an environmental origin and may have been inhaled and could have impacted his health and his Champagne and Aishihik First Nations (CAFN) contemporaries.

Using Raman spectroscopy to assess hemoglobin oxygenation in red blood cell concentrate: an objective proxy for morphological index to gauge the quality of stored blood?

Blood banking is an essential aspect of modern medical care. When red blood cells (RBCs) are stored, they become damaged by various chemical processes, such as accumulation of their own waste products and oxidative injury, among others. These processes lead to the development of the RBC storage lesion, a complex condition where the severity is reflected through the morphology of the stored cells. It was hypothesized that Raman spectroscopy could be used to monitor certain structural and compositional changes associated with such ageing effects and that a relationship between these features and traditional morphology (as measured using a morphology index) could be observed. The hypothesis was tested by measuring spectral features associated with hemoglobin oxygenation from dry-fixed smears and liquid RBCs for twenty-nine different donors (combined), and comparing the trends with morphological scoring from seven of these donors. After appropriately fitting the two data sets to either power or linear curves, the oxygenation state was shown to change in a manner that was donor-dependent and that closely tracked morphological changes. This study suggests Raman analysis has promise for providing a rapid and objective measure of the cell quality of stored RBCs through measurements of hemoglobin oxygenation that is comparable to traditional morphological assessment.

Prospective multicentre cohort study on 9154 surgical procedures to assess the risk of postoperative bleeding - a DESSI study.

BACKGROUND: To date, there is still a debate how to deal with patients receiving antithrombotic agents prior to surgical procedures on the skin. OBJECTIVE: To prospectively assess complications after dermatosurgical interventions, especially bleeding, depending on anticoagulation therapy. METHODS: Patients underwent surgery consecutively as scheduled, without randomization, whether or not they were currently taking anticoagulants. Nine institutions of the DESSI (DErmatoSurgical Study Initiative) working group documented patient data prospectively on a standardized study sheet prior to and after 9154 dermatosurgical interventions. RESULTS: Bleeding complications were observed in 7.14% of cases (654/9154 surgeries). A severe bleed requiring intervention by a physician occurred in 83 surgeries (0.91%). In multivariate analysis, INR, length of the defect, perioperative antibiotic treatment, current treatment with anticoagulation therapy, age and surgery on hidradenitis suppurativa/acne inversa (HS/AI) were significant parameters independently influencing the risk of bleeding. Discontinuation of phenprocoumon therapy and subsequent switching to low molecular weight heparin was associated with the highest risk of bleeding (9.26%). CONCLUSION: Bleeding complications in skin surgery are generally rare. Even if slightly increased complication rates are found in patients taking anticoagulants during skin surgery, platelet inhibitors should not be stopped prior to surgery. If a surgical procedure in patients on a combination therapy of 2 or more antiplatelet cannot be postponed, it should be conducted with the patient remaining on combination therapy. Discontinuation of DOACs is recommended 24 h prior to surgery. Bridging of phenprocoumon should be terminated. In patients with a bleeding history, the INR value should be within the therapeutic range.

[Neuromodulation using matrix stimulation : A treatment for acute pain?] / Neuromodulation mittels Matrixstimulation : Ein Therapieansatz für akute Schmerzen?

BACKGROUND: There is currently a lack of studies that evaluate the effects of matrix electrode neuromodulation on acute pain. In this prospective and randomized cross-over study, we investigated the efficacy of 4 Hz-matrix stimulation on venipuncture-induced pain in 30 healthy subjects. METHODS: We compared two conditions of neurostimulation: in EC1 (experimental condition 1), we performed venipuncture during stimulation, with 2.5 min of prestimulation with 600 stimuli; in EC2 (experimental condition 2), the length of stimulation was 5 min, at 1200 stimuli, with subsequent venipuncture. A group with no stimulation was used as control condition. RESULTS: The EC2 group did not only show a 77% reduction in puncture pain when compared to the control group (p < 0.001; effect size [ES] d = 1.45), but also had a significant effect compared with EC1 (p < 0.001; ES d = 1.33). EC1, on the other hand, did not demonstrate a significant difference to the control group. The status of the veins was evaluated based on visibility and did not differ significantly between the conditions. CONCLUSION: The results of this study showed for the first time that pre-emptive matrix stimulation could be an effective way to reduce acute pain. The duration of stimulation seems to play a key role in the effectiveness of the neurophysiological mechanism of action. Matrix stimulation is a therapeutic intervention with very few side effects, which could, in the future, expand our pain-management options for the treatment of acute pain.

Raman spectroscopy as a novel tool for monitoring biochemical changes and inter-donor variability in stored red blood cell units.

Individual units of donated red blood cells (RBCs) do not ordinarily undergo analytical testing prior to transfusion. This study establishes the utility of Raman spectroscopy for analyzing the biochemistry of stored RBC supernatant and reveals interesting storage-related changes about the accumulation of lactate, a chemical species that may be harmful to certain patients. The data show measurable variations in supernatant composition and demonstrate that some units of donated RBCs accumulate lactate much more readily than others. The spectra also indicate a higher relative concentration of lactate in units collected from male donors than female donors (p = 0.004) and imply that there is a greater degree of variability at later stages of storage in units from older male donors (>45 years). The study proves that Raman analysis has promise for elucidating the relationship between the metabolism of stored RBCs and donor characteristics. It also suggests that there may be benefit in developing a Raman instrument for the rapid non-invasive assessment of blood-bag biochemistry by measuring through plastic over-layers.

Non-invasive spectroscopy of transfusable red blood cells stored inside sealed plastic blood-bags.

After being separated from (donated) whole blood, red blood cells are suspended in specially formulated additive solutions and stored (at 4 °C) in polyvinyl chloride (PVC) blood-bags until they are needed for transfusion. With time, the prepared red cell concentrate (RCC) is known to undergo biochemical changes that lower effectiveness of the transfusion, and thus regulations are in place that limit the storage period to 42 days. At present, RCC is not subjected to analytical testing prior to transfusion. In this study, we use Spatially Offset Raman Spectroscopy (SORS) to probe, non-invasively, the biochemistry of RCC inside sealed blood-bags. The retrieved spectra compare well with conventional Raman spectra (of sampled aliquots) and are dominated by features associated with hemoglobin. In addition to the analytical demonstration that SORS can be used to retrieve RCC spectra from standard clinical blood-bags without breaking the sterility of the system, the data reveal interesting detail about the oxygenation-state of the stored cells themselves, namely that some blood-bags unexpectedly contain measurable amounts of deoxygenated hemoglobin after weeks of storage. The demonstration that chemical information can be obtained non-invasively using spectroscopy will enable new studies of RCC degeneration, and points the way to a Raman-based instrument for quality-control in a blood-bank or hospital setting.

Process Analytical Utility of Raman Microspectroscopy in the Directed Differentiation of Human Pancreatic Insulin-Positive Cells.

Continued advances toward cell-based therapies for human disease generate a growing need for unbiased and label-free monitoring of cellular characteristics. We used Raman microspectroscopy to characterize four important stages in the 26-day directed differentiation of human embryonic stem cells (hESCs) to insulin-positive cells. The extent to which the cells retained spectroscopic features of pluripotent cells or developed spectroscopic features suggestive of pancreatic endocrine cells, as well as assessing the homogeneity of the cell populations at these developmental stages, were of particular interest. Such information could have implications for the utility of Raman microspectroscopy process analysis for the generation of insulin-positive cells from hESCs. Because hESC seeding density influences the subsequent pancreatic development, three different seeding density cultures were analyzed. Transcription factor and other marker analyses assessed the progress of the cells through the relevant developmental stages. Increases in the Raman protein-to-nucleic acid band ratios were observed at the final endocrine stage analyzed, but this increase was less than expected. Also, high glycogen band intensities, somewhat unexpected in pancreatic endocrine cells, suggested the presence of a substantial number of glycogen containing cells. We discuss the potential process analytical technology application of these findings and their importance for cell manufacturing.

Silicon-gold-silica lamellar structures for sample substrates that provide an internal standard for Raman microspectroscopy.

Crystalline silicon, widely used in the electronic industry, is also a very popular material for calibrating Raman spectrometry instruments. Silicon chips cut or cleaved from commercially available silicon wafers are low-cost monolithic monocrystalline materials that give a strong Raman line at 521 cm(-1) with almost no background. Such chips have at least one optically flat surface and can be used in place of glass microscope slides as sample substrates that provide an internal calibration standard during Raman measurements. The Raman signal intensity from the silicon can be selectively attenuated by depositing a gold layer on top of the silicon surface with variable thickness such that the far-field silicon Raman signal is comparable with the Raman signal of an investigated material adjacent to this structure. This gold layer provides the additional advantage of increased sensitivity of the spectral signal from the sample due to the reflectivity of the gold surface, which allows forward and backscattered analyte Raman excitation and signal collection. An additional thin encapsulating overlayer of SiO2 provides a protective and biocompatible surface to facilitate Raman microspectroscopic investigation of live cells.