Responsive monitoring of mitochondrial redox states in heart muscle predicts impending cardiac arrest

Modern optical approaches in redox biology: Genetically encoded sensors and Raman spectroscopy

The objective of the current review is to summarize the current state of optical methods in redox biology. It consists of two parts, the first is dedicated to genetically encoded fluorescent indicators and the second to Raman spectroscopy. In the first part, we provide a detailed classification of the currently available redox biosensors based on their target analytes. We thoroughly discuss the main architecture types of these proteins, the underlying engineering strategies for their development, the biochemical properties of existing tools and their advantages and disadvantages from a practical point of view. Particular attention is paid to fluorescence lifetime imaging microscopy as a possible readout technique, since it is less prone to certain artifacts than traditional intensiometric measurements. In the second part, the characteristic Raman peaks of the most important redox intermediates are listed, and examples of how this knowledge can be implemented in biological studies are given. This part covers such fields as estimation of the redox states and concentrations of Fe-S clusters, cytochromes, other heme-containing proteins, oxidative derivatives of thiols, lipids, and nucleotides. Finally, we touch on the issue of multiparameter imaging, in which biosensors are combined with other visualization methods for simultaneous assessment of several cellular parameters.

Real-time monitoring of mitochondrial oxygenation during machine perfusion using resonance Raman spectroscopy predicts organ function

Organ transplantation is a life-saving procedure affecting over 100,000 people on the transplant waitlist. Ischemia reperfusion injury (IRI) is a major challenge in the field as it can cause post-transplantation complications and limit the use of organs from extended criteria donors. Machine perfusion technology has the potential to mitigate IRI; however, it currently fails to achieve its full potential due to a lack of highly sensitive and specific assays to assess organ quality during perfusion. We developed a real-time and non-invasive method of assessing organs during perfusion based on mitochondrial function and injury using resonance Raman spectroscopy. It uses a 441 nm laser and a high-resolution spectrometer to quantify the oxidation state of mitochondrial cytochromes during perfusion. This index of mitochondrial oxidation, or 3RMR, was used to understand differences in mitochondrial recovery of cold ischemic rodent livers during machine perfusion at normothermic temperatures with an acellular versus cellular perfusate. Measurement of the mitochondrial oxidation revealed that there was no difference in 3RMR of fresh livers as a function of normothermic perfusion when comparing acellular versus cellular-based perfusates. However, following 24 h of static cold storage, 3RMR returned to baseline faster with a cellular-based perfusate, yet 3RMR progressively increased during perfusion, indicating injury may develop over time. Thus, this study emphasizes the need for further refinement of a reoxygenation strategy during normothermic machine perfusion that considers cold ischemia durations, gradual recovery/rewarming, and risk of hemolysis.

Arch watch: current approaches and opportunities for improvement

Coarctation of the aorta (CoA) is a ductus arteriosus (DA)-dependent form of congenital heart disease (CHD) characterized by narrowing in the region of the aortic isthmus. CoA is a challenging diagnosis to make prenatally and is the critical cardiac lesion most likely to go undetected on the pulse oximetry-based newborn critical CHD screen. When undetected CoA causes obstruction to blood flow, life-threatening cardiovascular collapse may result, with a high burden of morbidity and mortality. Hemodynamic monitoring practices during DA closure (known as an "arch watch") vary across institutions and existing tools are often insensitive to developing arch obstruction. Novel measures of tissue oxygenation and oxygen deprivation may improve sensitivity and specificity for identifying evolving hemodynamic compromise in the newborn with CoA. We explore the benefits and limitations of existing and new tools to monitor the physiological changes of the aorta as the DA closes in infants at risk of CoA.

Cardiac multiscale bioimaging: from nano- through micro- to mesoscales

Cardiac multiscale bioimaging is an emerging field that aims to provide a comprehensive understanding of the heart and its functions at various levels, from the molecular to the entire organ. It combines both physiologically and clinically relevant dimensions: from nano- and micrometer resolution imaging based on vibrational spectroscopy and high-resolution microscopy to assess molecular processes in cardiac cells and myocardial tissue, to mesoscale structural investigations to improve the understanding of cardiac (patho)physiology. Tailored super-resolution deep microscopy with advanced proteomic methods and hands-on experience are thus strategically combined to improve the quality of cardiovascular research and support future medical decision-making by gaining additional biomolecular information for translational and diagnostic applications.

Normothermic Ex Situ Machine Perfusion of Vascularized Composite Allografts with Oxygen Microcarriers for 12 Hours Using Real-Time Mitochondrial Redox Quantification

BACKGROUND

Normothermic ex situ perfusion of vascularized composite allografts (VCAs) necessitates high oxygen demand and, thus, increased metabolic activity, which, in turn, requires the use of blood-based perfusion solutions. However, blood-derived perfusates, in turn, constitute an antigenic load. To circumvent this immunogenic problem, we used a perfusate enriched with acellular dextrane oxygen microcarriers to perfuse rat hindlimbs.

METHODS

Rat hindlimbs (n = 11) were perfused with either (non-), oxygenated dextrane-enriched Phoxilium, or Phoxilium enriched with dextrane oxygen microcarriers (MO2) for 12 h at 37 °C or stored on ice. Oxygenation of the skeletal muscle was assessed with Raman spectroscopy, tissue pO2-probes, and analysis of the perfusate. Transmission electronic microscopy was utilized to assess the ultrastructure of mitochondria of the skeletal muscle.

RESULTS

For all evaluated conditions, ischemia time until perfusion was comparable (22.91 ± 1.64 min; p = 0.1559). After 12 h, limb weight increased significantly by at least 81%, up to 124% in the perfusion groups, and by 27% in the static cold storage (SCS) group. Raman spectroscopy signals of skeletal muscle did not differ substantially among the groups during either perfusion or static cold storage across the duration of the experiment. While the total number of skeletal muscle mitochondria decreased significantly compared to baseline, mitochondrial diameter increased in the perfusion groups and the static cold storage group.

CONCLUSION

The use of oxygen microcarriers in ex situ perfusion of VCA with acellular perfusates under normothermic conditions for 12 h facilitates the maintenance of mitochondrial structure, as well as a subsequent recovery of mitochondrial redox status over time, while markers of muscle injury were lower compared to conventional oxygenated acellular perfusates.

Novel Imaging Technologies for Accurate Assessment of Cardiac Allograft Performance

Purpose of the Review

The current lack of objective and quantitative assessment techniques to determine cardiac graft relative viability results in risk-averse decision-making, which negatively impact the utilization of cardiac grafts. The purpose of this review is to highlight the current deficiencies in cardiac allograft assessment before focusing on novel cardiac assessment techniques that exploit conventional and emerging imaging modalities, including ultrasound, magnetic resonance, and spectroscopy.

Recent Findings

Extensive work is ongoing by the scientific community to identify improved objective metrics and tools for cardiac graft assessment, with the goal to safely increasing the number and proportion of hearts accepted for transplantation.

Summary

This review briefly discusses the in situ and ex vivo tools currently available for clinical organ assessment, before focusing on the individual capabilities of ultrasound, magnetic resonance, and spectroscopy to provide insightful, non-invasive information regarding cardiac graft functional and metabolic status that may be used to predict outcome after transplantation.

In vivo noninvasive mitochondrial redox assessment of the optic nerve head to predict disease

Eye diseases are diagnosed by visualizing often irreversible structural changes occurring late in disease progression, such as retinal ganglion cell loss in glaucoma. The retina and optic nerve head have high mitochondrial energy need. Early mitochondrial/energetics dysfunction may predict vulnerability to permanent structural changes. In the in vivo murine eye, we used light-based resonance Raman spectroscopy (RRS) to assess noninvasively the redox states of mitochondria and hemoglobin which reflect availability of electron donors (fuel) and acceptors (oxygen). As proof of principle, we demonstrated that the mitochondrial redox state at the optic nerve head correlates with later retinal ganglion loss after acute intraocular pressure (IOP) elevation. This technology can potentially map the metabolic health of eye tissue in vivo complementary to optical coherence tomography, defining structural changes. Early detection (and normalization) of mitochondrial dysfunction before irreversible damage could lead to prevention of permanent neural loss.

SERS uncovers the link between conformation of cytochrome c heme and mitochondrial membrane potential

The balance between the mitochondrial respiratory chain activity and the cell's needs in ATP ensures optimal cellular function. Cytochrome c is an essential component of the electron transport chain (ETC), which regulates ETC activity, oxygen consumption, ATP synthesis and can initiate apoptosis. The impact of conformational changes in cytochrome c on its function is not understood for the lack of access to these changes in intact mitochondria. We have developed a novel sensor that uses unique properties of label-free surface-enhanced Raman spectroscopy (SERS) to identify conformational changes in heme of cytochrome c and to elucidate their role in functioning mitochondria. We have verified that molecule bond vibrations assessed by SERS are a reliable indicator of the heme conformation during changes in the inner mitochondrial membrane potential and ETC activity. We have demonstrated that cytochrome c heme reversibly switches between planar and ruffled conformations in response to the inner mitochondrial membrane potential (ΔΨ) and H⁺ concentration in the intermembrane space. This regulates the efficiency of the mitochondrial respiratory chain, thus, adjusting the mitochondrial respiration to the cell's consumption of ATP and the overall activity. We have found that under hypertensive conditions cytochrome c heme loses its sensitivity to ΔΨ that can affect the regulation of ETC activity. The ability of the proposed SERS-based sensor to track mitochondrial function opens broad perspectives in cell bioenergetics.

A high-fat diet changes astrocytic metabolism to promote synaptic plasticity and behavior

AIM

A high-fat diet (HFD) is generally considered to negatively influence the body, the brain, and cognition. Nonetheless, fat and fatty acids are essential for nourishing and constructing brain tissue. Astrocytes are central for lipolysis and fatty acids metabolism. We tested how HFD affects astrocyte metabolism, morphology, and physiology.

METHODS

We used Raman microspectroscopy to assess the redox state of mitochondria and lipid content in astrocytes and neurons in hippocampal slices of mice subjected to HFD. Astrocytes were loaded with fluorescent dye through patch pipette for morphological analysis. Whole-cell voltage-clamp recordings were performed to measure transporter and potassium currents. Western blot analysis quantified the expression of astrocyte-specific proteins. Field potential recordings measured the magnitude of long-term potentiation (LTP). Open filed test was performed to evaluate the effect of HFD on animal behavior.

RESULTS

We found that exposure of young mice to 1 month of HFD increases lipid content and relative amount of reduced cytochromes in astrocytes but not in neurons. Metabolic changes were paralleled with an enlargement of astrocytic territorial domains due to an increased outgrowth of branches and leaflets. Astrocyte remodeling was associated with an increase in expression of ezrin and with no changes in glial fibrillary acidic protein (GFAP), glutamate transporter-1 (GLT-1), and glutamine synthetase (GS). Such physiological (non-reactive) enlargement of astrocytes in the brain active milieu promoted glutamate clearance and LTP and translated into behavioral changes.

CONCLUSION

Dietary fat intake is not invariably harmful and might exert beneficial effects depending on the biological context.

Label-free in vivo assessment of brain mitochondrial redox states during the development of diabetic cognitive impairment using Raman spectroscopy

Mitochondrial redox imbalance has been recognized as a unifying cause for diabetic cognitive impairment. Currently, a robust method for the in vivo assessment of brain mitochondrial redox imbalance is still lacking. Here, we conducted a spectral study to assess brain mitochondrial redox imbalance in the process of diabetic cognitive impairment by using label-free resonance Raman spectroscopy (RRS). Our findings showed that mitochondrial redox imbalance in cultured neurons and organotypic cortical slices exposed to high glucose were quantified by the reduction of Raman peak area at 750 cm^-1 and 1128 cm^-1, which were also associated with synaptic injury and neuron apoptosis. Raman peak area at 750 cm^-1 and 1128 cm^-1 were also decreased in db/db mice at the age of 8, 16 and 24 weeks, and had a high correlation with the mitochondrial NAD⁺/NADH redox couple. Of note, this mitochondrial redox imbalance occurred before measurable cognitive decline in 8-week-old diabetic mice, and might signal impending diabetic cognitive impairment. In summary, RRS-based mitochondrial redox states assay enabled the in vivo assessment of brain mitochondrial redox imbalance, and might provide an early indicator to enhance the prediction of diabetic cognitive impairment and inform on the response to therapies targeting mitochondrial redox imbalance.

Non-invasive quantification of the mitochondrial redox state in livers during machine perfusion

Ischemia reperfusion injury (IRI) is a critical problem in liver transplantation that can lead to life-threatening complications and substantially limit the utilization of livers for transplantation. However, because there are no early diagnostics available, fulminant injury may only become evident post-transplant. Mitochondria play a central role in IRI and are an ideal diagnostic target. During ischemia, changes in the mitochondrial redox state form the first link in the chain of events that lead to IRI. In this study we used resonance Raman spectroscopy to provide a rapid, non-invasive, and label-free diagnostic for quantification of the hepatic mitochondrial redox status. We show this diagnostic can be used to significantly distinguish transplantable versus non-transplantable ischemically injured rat livers during oxygenated machine perfusion and demonstrate spatial differences in the response of mitochondrial redox to ischemia reperfusion. This novel diagnostic may be used in the future to predict the viability of human livers for transplantation and as a tool to better understand the mechanisms of hepatic IRI.

The Effect of Ethanol Consumption on Composition and Morphology of Femur Cortical Bone in Wild-Type and ALDH2*2-Homozygous Mice

ALDH2 inactivating mutation (ALDH2*2) is the most abundant mutation leading to bone morphological aberration. Osteoporosis has long been associated with changes in bone biomaterial in elderly populations. Such changes can be exacerbated with elevated ethanol consumption and in subjects with impaired ethanol metabolism, such as carriers of aldehyde dehydrogenase 2 (ALDH2)-deficient gene, ALDH2*2. So far, little is known about bone compositional changes besides a decrease in mineralization. Raman spectroscopic imaging has been utilized to study the changes in overall composition of C57BL/6 female femur bone sections, as well as in compound spatial distribution. Raman maps of bone sections were analyzed using multilinear regression with these four isolated components, resulting in maps of their relative distribution. A 15-week treatment of both wild-type (WT) and ALDH2*2/*2 mice with 20% ethanol in the drinking water resulted in a significantly lower mineral content (p < 0.05) in the bones. There was no significant change in mineral and collagen content due to the mutation alone (p > 0.4). Highly localized islets of elongated adipose tissue were observed on most maps. Elevated fat content was found in ALDH2*2 knock-in mice consuming ethanol (p < 0.0001) and this effect appeared cumulative. This work conclusively demonstrates that that osteocytes in femurs of older female mice accumulate fat, as has been previously theorized, and that fat accumulation is likely modulated by levels of acetaldehyde, the ethanol metabolite.

Shock Index, Coronary Perfusion Pressure, and Rate Pressure Product As Predictors of Adverse Outcome After Pediatric Cardiac Surgery

OBJECTIVES

To determine whether shock index, coronary perfusion pressure, or rate pressure product in the first 24 hours after congenital heart surgery are independent predictors of subsequent clinically significant adverse outcomes.

DESIGN

A retrospective cohort study.

SETTING

A tertiary care center.

PATIENTS

All patients less than 18 years old who underwent cardiac surgery at Boston Children's Hospital between January 1, 2010, and December 31, 2018.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Shock index (heart rate/systolic blood pressure), coronary perfusion pressure (diastolic blood pressure-right atrial pressure), and rate pressure product (heart rate × systolic blood pressure) were calculated every 5 seconds, and the median value for the first 24 hours of cardiac ICU admission for each was used as a predictor. The composite, primary outcome was the occurrence of any of the following adverse events in the first 7 days following cardiac ICU admission: cardiopulmonary resuscitation, extracorporeal cardiopulmonary resuscitation, mechanical circulatory support, unplanned surgery, heart transplant, or death. The association of each variable of interest with this outcome was tested in a multivariate logistic regression model. Of the 4,161 patients included, 296 (7%) met the outcome within the specified timeframe. In a multivariate regression model adjusted for age, surgical complexity, inotropic and respiratory support, and organ dysfunction, shock index greater than 1.83 was significantly associated with the primary outcome (odds ratio, 6.6; 95% CI, 4.4-10.0), and coronary perfusion pressure greater than 35 mm Hg was protective against the outcome (odds ratio, 0.5; 0.4-0.7). Rate pressure product was not found to be associated with the outcome. However, the predictive ability of the shock index and coronary perfusion pressure models were not superior to their component hemodynamic variables alone.

CONCLUSIONS

Both shock index and coronary perfusion pressure may offer predictive value for adverse outcomes following cardiac surgery in children, although they are not superior to the primary hemodynamic variables.

Sensitivity of a Next-Generation NIRS Device to Detect Low Mixed Venous Oxyhemoglobin Saturations in the Single Ventricle Population

Regional cerebral oxygenation index (rSO2) based on near-infrared spectroscopy (NIRS) is frequently used to detect low venous oxyhemoglobin saturation (ScvO2). We compared the performance of 2 generations of NIRS devices. Clinically obtained, time-matched cerebral rSO2 and ScvO2 values were compared in infants monitored with the FORE-SIGHT (n = 73) or FORE-SIGHT ELITE (n = 47) by linear regression and Bland-Altman analyses. In both devices, cerebral rSO2 correlated poorly with measured ScvO2 (FORE-SIGHT partial correlation 0.50 [95% confidence interval {CI}, 0.40-0.58]; FORE-SIGHT ELITE partial correlation 0.47 [0.39-0.55]) and mean bias was +8 (standard deviation [SD] 13.2) for FORE-SIGHT and +14 (SD 12.5) for FORE-SIGHT ELITE. When ScvO2 was <30%, rSO2 was <40 in 8% of FORE-SIGHT ELITE readings. Future NIRS should be validated in more hypoxic cohorts.

Mitochondria and the thermal limits of ectotherms

Temperature is a critical abiotic factor shaping the distribution and abundance of species, but the mechanisms that underpin organismal thermal limits remain poorly understood. One possible mechanism underlying these limits is the failure of mitochondrial processes, as mitochondria play a crucial role in animals as the primary site of ATP production. Conventional measures of mitochondrial performance suggest that these organelles can function at temperatures much higher than those that limit whole-organism function, suggesting that they are unlikely to set organismal thermal limits. However, this conclusion is challenged by recent data connecting sequence variation in mitochondrial genes to whole-organism thermal tolerance. Here, we review the current state of knowledge of mitochondrial responses to thermal extremes and ask whether they are consistent with a role for mitochondrial function in shaping whole-organism thermal limits. The available data are fragmentary, but it is possible to draw some conclusions. There is little evidence that failure of maximal mitochondrial oxidative capacity as assessed in vitro sets thermal limits, but there is some evidence to suggest that temperature effects on ATP synthetic capacity may be important. Several studies suggest that loss of mitochondrial coupling is associated with the thermal limits for organismal growth, although this needs to be rigorously tested. Most studies have utilized isolated mitochondrial preparations to assess the effects of temperature on these organelles, and there remain many untapped opportunities to address these questions using preparations that retain more of their biological context to better connect these subcellular processes with whole-organism thermal limits.

Early label-free analysis of mitochondrial redox states by Raman spectroscopy predicts septic outcomes

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Resonance Raman spectroscopy was applied to in vivo detection of the mitochondrial redox state in septic mice for the first time.

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Monitoring mitochondrial redox states using resonance Raman spectroscopy had higher prognostic accuracy for mortality than the lactate level during sepsis and could be a novel diagnostic marker for predicting septic outcomes at an early time point.

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Resonance Raman spectroscopy could detect mitochondrial dysfunction in sepsis and provide a biomarker that can be a specific target of adjunctive treatment.

Background

Sepsis remains an unacceptably high mortality due to the lack of biomarkers for predicting septic outcomes in the early period. Mitochondrial redox states play a pivotal role in this condition and are disturbed early in the development of sepsis. Here, we hypothesized that visualizing mitochondrial redox states via resonance Raman spectroscopy (RRS) could identify septic outcomes at an early time point. Sepsis was induced by cecal ligation and puncture (CLP). We applied RRS analysis at baseline and 30 min, 1 h, 2 h, 4 h, and 6 h after CLP, and the mitochondrial redox states were identified. The levels of blood lactate as a predictor in sepsis were assessed. Our study is the first to reveal the possibility of in vivo detection of the mitochondrial redox state by using RRS in septic mice. The peak area for the Raman reduced mitochondrial fraction, the indicator of mitochondrial redox states, fluctuated significantly at 2 h after CLP. This fluctuation occurred earlier than the change in lactate level. Moreover, this fluctuation had higher prognostic accuracy for mortality than the lactate level during sepsis and could be a novel diagnostic marker for predicting septic outcomes according to the cutoff value of 1.059, which had a sensitivity of 80% and a specificity of 90%.

Objectives

To explore an effective indicator concerning mitochondrial redox states in the early stage of sepsis and to predict septic outcomes accurately in vivo using non-invasive and label-free Resonance Raman spectroscopy (RRS) analysis.

Methods

Mitochondria, primary skeletal muscle cells andex-vivo muscles harvested from gastrocnemius were detected mitochondrial redox states respectively by using RRS. Sepsis was induced by cecal ligation and puncture (CLP). We applied RRS analysis at baseline and 30 min, 1 h, 2 h, 4 h, and 6 h after CLP, and the mitochondrial redox states were identified. The levels of blood lactate as a predictor in sepsis were assessed. The predictive correlation of mitochondrial redox states on mortality, inflammation and organ dysfunction was further assessed.

Results

Mitochondrial redox states were clearly recognized in ex-vivo gastrocnemius muscles as well as purified mitochondria and primary skeletal muscle cells by using RRS. The peak area for the Raman reduced mitochondrial fraction, the indicator of mitochondrial redox states, fluctuated significantly at 2 h after CLP. This fluctuation occurred earlier than the change in lactate level. Moreover, this fluctuation had higher prognostic accuracy for mortality than the lactate level during sepsis and could be a novel diagnostic marker for predicting septic outcomes according to the cutoff value of 1.059, which had a sensitivity of 80% and a specificity of 90%.

Conclusions

This study demonstrated that monitoring mitochondrial redox states using RRS as early as 2 h could indicate outcomes in septic mice. These data may contribute to developing a non-invasive clinical device concerning mitochondrial redox states by using bedside-RRS.

The role of the myeloperoxidase-derived oxidant hypothiocyanous acid (HOSCN) in the induction of mitochondrial dysfunction in macrophages

A host of chronic inflammatory diseases are accelerated by the formation of the powerful oxidant hypochlorous acid (HOCl) by myeloperoxidase (MPO). In the presence of thiocyanate (SCN^-), the production of HOCl by MPO is decreased in favour of the formation of a milder oxidant, hypothiocyanous acid (HOSCN). The role of HOSCN in disease has not been fully elucidated, though there is increasing interest in using SCN^- therapeutically in different disease settings. Unlike HOCl, HOSCN can be detoxified by thioredoxin reductase, and reacts selectively with thiols to result in reversible modifications, which could potentially reduce the extent of MPO-induced damage during chronic inflammation. In this study, we show that exposure of macrophages, a key inflammatory cell type, to HOSCN results in the reversible modification of multiple mitochondrial proteins, leading to increased mitochondrial membrane permeability, decreased oxidative phosphorylation and reduced formation of ATP. The increased permeability and reduction in ATP could be reversed by pre-treatment of the macrophages with cyclosporine A, implicating a role for the mitochondrial permeability transition pore. HOSCN also drives cells to utilise fatty acids as an energetic substrate after the inhibition of oxidative phosphorylation. Raman imaging studies highlighted the ability of HOSCN to perturb the electron transport chain of mitochondria and redistribute these organelles within the cell. Taken together, these data provide new insight into the pathways by which HOSCN can induce cytotoxicity and cellular damage, which may have relevance for the development of inflammatory disease, and therapeutic strategies to reduce HOCl-induced damage by supplementation with SCN^-.

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HOSCN induces the oxidation of mitochondrial thiol proteins and cytochromes.

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HOSCN alters mitochondrial permeability and ATP production via MPTP formation.

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HOSCN increases the capacity of cells to use fatty acids as an energetic substrate.

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Raman imaging shows redistribution of mitochondria after cell exposure to HOSCN.

Determination of cadmium induced acute and chronic reproductive toxicity with Raman spectroscopy

Cadmium (Cd) is one of the toxic heavy metals which is confirmed to be related to male sterile. Here, confocal Raman spectroscopy was employed to detect biomolecular composition and changes in testis under acute and chronic Cd treatment. Specific Raman shifts associated with mitochondria, nucleic acids, proteins, lipids, and cholesterol were identified which were distinguishing among groups undergoing different Cd treatment times. Supporting evidences were provided by conventional experimental detections. The relevant biochemical parameters, pathological changes, and protein expression related to testosterone synthesis were all changed and consistent with Raman spectrum information. In conclusion, confocal Raman spectroscopy presents a reliable data and provides a novel method which is expected to be a promising strategy in reproduction toxicity research.

Raman Scattering: From Structural Biology to Medical Applications

This is a review of relevant Raman spectroscopy (RS) techniques and their use in structural biology, biophysics, cells, and tissues imaging towards development of various medical diagnostic tools, drug design, and other medical applications. Classical and contemporary structural studies of different water-soluble and membrane proteins, DNA, RNA, and their interactions and behavior in different systems were analyzed in terms of applicability of RS techniques and their complementarity to other corresponding methods. We show that RS is a powerful method that links the fundamental structural biology and its medical applications in cancer, cardiovascular, neurodegenerative, atherosclerotic, and other diseases. In particular, the key roles of RS in modern technologies of structure-based drug design are the detection and imaging of membrane protein microcrystals with the help of coherent anti-Stokes Raman scattering (CARS), which would help to further the development of protein structural crystallography and would result in a number of novel high-resolution structures of membrane proteins—drug targets; and, structural studies of photoactive membrane proteins (rhodopsins, photoreceptors, etc.) for the development of new optogenetic tools. Physical background and biomedical applications of spontaneous, stimulated, resonant, and surface- and tip-enhanced RS are also discussed. All of these techniques have been extensively developed during recent several decades. A number of interesting applications of CARS, resonant, and surface-enhanced Raman spectroscopy methods are also discussed.

Ex vivo detection of cadmium-induced renal damage by using confocal Raman spectroscopy

Cadmium (Cd) is a toxic heavy metal which is harmful to environment and organisms. The reabsorption of Cd in kidney leads it to be the main damaged organ in animals under the Cd exposure. In this work, we applied confocal Raman spectroscopy to map the pathological changes in situ in normal and Cd-exposed mice kidney. The renal tissue from Cd-exposed group displayed a remarkable decreasing in the intensity of typical peaks related to mitochondria, DNA, proteins and lipids. On the contrary, the peaks of collagen in Cd-exposed group elevated significantly. The components in each tissue were identified and distinguished by principal component analysis. Furthermore, all the biological investigations in this study were consistent with the Raman spectrum detection, which revealed the progression and degree of lesion induced by Cd. The confocal Raman spectroscopy provides a new perspective for in situ monitoring of substances changes in tissues, which exhibits more comprehensive understanding of the pathogenic mechanisms of heavy metals in molecular toxicology.

Optical biopsy identification and grading of gliomas using label-free visible resonance Raman spectroscopy

Glioma is one of the most refractory types of brain tumor. Accurate tumor boundary identification and complete resection of the tumor are essential for glioma removal during brain surgery. We present a method based on visible resonance Raman (VRR) spectroscopy to identify glioma margins and grades. A set of diagnostic spectral biomarkers features are presented based on tissue composition changes revealed by VRR. The Raman spectra include molecular vibrational fingerprints of carotenoids, tryptophan, amide I/II/III, proteins, and lipids. These basic in situ spectral biomarkers are used to identify the tissue from the interface between brain cancer and normal tissue and to evaluate glioma grades. The VRR spectra are also analyzed using principal component analysis for dimension reduction and feature detection and support vector machine for classification. The cross-validated sensitivity, specificity, and accuracy are found to be 100%, 96.3%, and 99.6% to distinguish glioma tissues from normal brain tissues, respectively. The area under the receiver operating characteristic curve for the classification is about 1.0. The accuracies to distinguish normal, low grade (grades I and II), and high grade (grades III and IV) gliomas are found to be 96.3%, 53.7%, and 84.1% for the three groups, respectively, along with a total accuracy of 75.1%. A set of criteria for differentiating normal human brain tissues from normal control tissues is proposed and used to identify brain cancer margins, yielding a diagnostic sensitivity of 100% and specificity of 71%. Our study demonstrates the potential of VRR as a label-free optical molecular histopathology method used for in situ boundary line judgment for brain surgery in the margins.

Polymer Therapeutics: Biomarkers and New Approaches for Personalized Cancer Treatment

Polymer therapeutics (PTs) provides a potentially exciting approach for the treatment of many diseases by enhancing aqueous solubility and altering drug pharmacokinetics at both the whole organism and subcellular level leading to improved therapeutic outcomes. However, the failure of many polymer-drug conjugates in clinical trials suggests that we may need to stratify patients in order to match each patient to the right PT. In this concise review, we hope to assess potential PT-specific biomarkers for cancer treatment, with a focus on new studies, detection methods, new models and the opportunities this knowledge will bring for the development of novel PT-based anti-cancer strategies. We discuss the various "hurdles" that a given PT faces on its passage from the syringe to the tumor (and beyond), including the passage through the bloodstream, tumor targeting, tumor uptake and the intracellular release of the active agent. However, we also discuss other relevant concepts and new considerations in the field, which we hope will provide new insight into the possible applications of PT-related biomarkers.