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Treating global diseases is a challenging task for researchers worldwide. For successful treatment, precise diagnostics as well as efficient therapies are crucial. Both diagnostic as well as therapeutic approaches require molecular or colloidal agents to either improve resolution and contrast for imaging or improve the efficacy of a drug or delivery vehicle. A novel idea, which has been pursued for some time, is the combination of imaging and drug delivery functions in one type of nanomaterial. This new research area is referred to as theranostics – the combination of therapy and diagnostics. The presented dissertation introduces conjugated polymer nanoparticles as theranostic agents. Starting from classical dye molecules in the first chapter, croconic acid is used in combination with diamines as a basis for unprecedented conjugated polymers. The well-known concept of dispersion polymerization is utilized to synthesize croconaine-based particles in a simple way at mild reaction conditions employing easy accessible reactants. The obtained particles exhibit high photoacoustic signal. Photoacoustic imaging is a novel technique that is gaining importance in clinical applications in recent years. In addition to their good optical properties, the particles exhibit excellent biocompatibility, making them a promising material for biomedical imaging applications. Following the overall aim to develop theranostic nanoparticles, in the next chapter, particles consisting of pure imidazole polymers are established. For this synthesis, direct arylation is applied as a polycondensation. The use of this synthetic route for the preparation of conjugated polymer particles is unprecedented and provides an atom economic alternative to classical C-C coupling reactions such as Suzuki, Heck, or Sonogashira, which are commonly used for the preparation of polymer particles. Adjustment of the particle diameter is analyzed in detail, because the size of a theranostic nanomaterial is decisive with respect to the targeting strategy. Our particle diameters can be tuned between ~ 50 nm and several hundreds of nanometers. Furthermore, the variation of the type of monomer allows the design of particles composed of either linear or cross-linked polymers. This structural handle can be used for tailoring the optical properties of the particles and thus the applicability for photoacoustic or fluorescence imaging. Using nanosized materials as contrast agents has the advantage that precise and detailed visualization of the stained tissue is possible. A disadvantage is that nanoparticles can accumulate in organs and may lead to toxic effects, short-term and long-term. Therefore, the application of degradable particles may lead to better biocompatibility in the long term, while the degradable units also offer the possibility to introduce a release mechanism. Imidazole can undergo oxidative degradation when being exposed to reactive oxygen species available in the body. Therefore, the functionalization of imidazole as a degradable building block for polymers makes it possible to design π-conjugated particles that can be cleaved into small molecules in a suitable bio-microenvironment. This hypothesis is verified using the developed polyimidazole particles in detailed cell experiments. The final step to make such imidazole-based particles theranostic, is by incorporation of a suitable drug as cargo. For this aim, the anti-cancer drug lenvatinib is synthetically modified in such a way so that it becomes polymerizable. Imidazole is used as a so-called prodrug moiety, since its suitability as a degradable moiety has been verified in the previous chapter. The prodrug molecule is incorporated into imidazole polymer particles by the means of direct arylation polymerization conducted as a dispersion polymerization. Precise quantification of the release in biological environments is a difficult task, which is why we first employ standardized conditions, using hydrogen peroxide as a single reactive oxygen species to degrade the particles. The degradation products are analyzed in detail, where apart from many small degradation products of the polymer particles, lenvatinib can be detected in its active form, proving the applicability of our concept for drug delivery system.

Plasmonic nanoparticles can be used in photothermal therapy thanks to their ability to generate local heat. The light-to-heat conversion efficiency is crucial for therapeutic and diagnostic applica...

The detection sensitivity of optoacoustic spectroscopy at the short-wavelength infrared (SWIR) region is reduced by water absorption in aqueous solutions. Our work reports marked improvements in the sensitivity of optoacoustic spectroscopic measurements of proteins, lipids, and glucose when performed at 4 °C, compared to conventional optoacoustic or IR spectroscopy. Studying the effect of water temperature on optoacoustic signals revealed a polarity change at temperatures below 4 °C (muting temperature). The dependence of the optoacoustic signal and the muting temperature on sample concentration were further investigated, demonstrating that changes in these dependencies enable accurate quantification of the solute concentration.

Human exhaled breath consists of more than 3000 volatile organic compounds, many of which are relevant biomarkers for various diseases. Although gas chromatography has been the gold standard for volatile organic compound (VOC) detection in exhaled breath, recent developments in mid-infrared (MIR) laser spectroscopy have led to the promise of compact point-of-care (POC) optical instruments enabling even single breath diagnostics. In this review, we discuss the evolution of MIR sensing technologies with a special focus on photoacoustic spectroscopy, and its application in exhaled breath biomarker detection. While mid-infrared point-of-care instrumentation promises high sensitivity and inherent molecular selectivity, the lack of standardization of the various techniques has to be overcome for translating these techniques into more widespread real-time clinical use.

The multispectral modality and technique for optically dense samples of optoacoustic spectroscopy were applied to measure spectra and high absorbances of concentrated aqueous dispersions of undoped nanodiamonds. The data from optoacoustic and optical transmission measurements and DSC data of the mean particle size by the Gibbs–Kelvin equation are compared to estimate the difference in composition of various nanodiamond trademarks. Optoacoustic spectra confirm the contribution of surface dimer chains into the absorption of nanodiamonds in the long wavelength range. Optoacoustic and conventional absorption spectra of aqueous solutions of nanodiamond fractions after centrifugation (15300g) and ultracentrifugation (130000g) revealed a separation of a highly absorbing non-diamond sp2 phase. The two-step separation by ultracentrifugation followed by extra centrifugation made it possible to isolate a highly absorbing and soluble nanodiamond phase with the particle size of 3.6 nm, showing a change in spectra compared to the starting nanodiamond material. Keywords: Optoacoustic spectroscopy, Multispectral optoacoustic spectroscopy, Optically dense samples, Nanodiamonds, Nanodiamond aqueous dispersions, Nanodiamond fractionation

In the development and optimization of imaging methods, photoacoustic imaging (PAI) has become a powerful tool for preclinical biomedical diagnosis and detection of cancer. PAI probes can improve contrast and help identify pathogenic tissue. Such contrast agents must meet several requirements: they need to be biocompatible, and absorb strongly in the near-infrared (NIR) range, while relaxing the photoexcited state thermally and not radiatively. In this work, polymer nanoparticles are produced with croconaine as a monomer unit. Small molecular croconaine dyes are known to act as efficient pigments, which do not show photoluminescence. Here, for the first time croconaine copolymer nanoparticles are produced from croconic acid and a range of aromatic diamines. Following a dispersion polymerization protocol, this approach yields monodisperse particles of adjustable size. All synthesized polymers exhibit broad absorption within the NIR spectrum and therefore represent suitable candidates as contrast agents for PAI. The optical properties of these polymer particles are discussed with respect to the relation between particle size and outstanding photoacoustic performance. Biocompatibility of the polymer particles is demonstrated in cell viability experiments., publishedVersion

Review sums up the application of photoacoustic and photothermal spectroscopies for the analysis and characterization of soils and soil organic matter and discusses the outlooks in this area. Keywords: Photoacoustic spectroscopy, Optoacoustic spectroscopy, Photothermal spectroscopy, Probe microspectroscopy, Soil, Soil organic matter, Dispersed organic matter

Control over volatile products of metabolic processes in human body in exhaled air is a promising method for noninvasive medical diagnostics. The mid-IR range (2 – 12 mm) is of great interest for diagnostic applications of the exhaled air spectral analysis. Laser optoacoustic spectroscopy is quite attractive for detecting a large set of gaseous substances; however, high-power sources of tunable radiation are required to increase the method sensitivity. We consider the possibility of using a parametric light generator based on a BaGa4Se7 crystal as a broadband tunable mid-IR laser source for laser optoacoustic spectroscopy.

Agradecimentos: This work was supported by research grants SIP-IPN (20170545 and 20181764) and CONACyT (2015-02-1042, 264093, 2016-01-2482). A. M. M. acknowledges the support of the Brazilian Agencies CNPq and FAPESP. The support of COFAA-IPN by the SIBE and BEIFI programs is also acknowledged Abstract: The phase-resolved method has been widely used in photoacoustic spectroscopy for separating the contribution of different optical absorption centers to a spectrum. However, the procedure is lengthy, tedious and without precision control, because one has to calculate several spectra to search for the phase angle at which only one contribution is present every time. In this work, this limitation is avoided by the implementation of a method as a search and optimization problem using the Hill Climbing Metaheuristic Algorithm. As test examples, the photoacoustic spectra of chilli fruit skin of Anaheim type (Capsicum Annuum L.) and yellow corn grain pericarp of dent type (Zea Mays L.) were analyzed in the wavelength ranges where there is optical absorption of the photoprotective pigments of these samples CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Breast cancer accounts for 30% of all cancer in women with an estimated 266,000 new cases and over 40,000 deaths in 2018. In the U.S., breast cancer treatments exceed $16.5 billion per year. The gold standard for treatment commonly involves a combination of breast conserving surgery and radiation. Treatments are only successful if the cancers are accurately detected. Breast cancers detection is commonly done through mammography or manual palpation. While mammography has reduced the death rate and allowed for earlier treatments, it is limited by dense breast tissue. Furthermore, about 50% of women experience false-positives. It is reported that approximately 30% of early stage breast cancer, also referred to as ductal carcinoma in situ (DCIS), is over diagnosed and overtreated, causing physical and emotional distress. This thesis aims to address the clinical need for predictive precursors for the aggressiveness and development of DCIS to invasive breast cancer by measuring tissue oxygenation and perfusion using photoacoustic and contrast-enhanced ultrasound imaging. Furthermore, exercise has been proposed as a mechanism to not only reduce the risk of breast cancer, but its progression as well. Therefore, the effects of voluntary physical exercise will be evaluated through the aforementioned parameters above. Mouse models consisting of FVB/NJ mice (n=20) and Tg(C3-1-TAg)cJeg mice (n=10) were evenly divided into exercise and control subgroups, where the exercise groups had access to an exercise wheel. The Tg(C3-1-TAg)cJeg (SV40 Tag) mouseline is genetically predisposed to develop DCIS. Mice were weighed biweekly. Tissue perfusion was measured using the combination of ultrasound contrast agents and high frequency nonlinear imaging. Time intensity curves were generated from perfusion flow within tumor ROIs to extract wash-in rate and area under the curve values. Average SO2 values were compared for tissue oxygenation from photoacoustic images. There was a significant difference between the exercise and control subgroups for the FVB/NJ and SV40 Tag mice. For the FVB/NJ mice, the exercise group exhibited lower weight changes than the control group (0.43 ± 0.70 g vs. 0.99 ± 2.31 g, respectively, p = 0.002). The SV40 Tag mice demonstrated similar differences in weight gain (2.67 ± 1.38 g vs. 3.36 ± 1.36 g, respectively, p = 0.006). There were no differences between the exercise and control subgroups of the FVB/NJ mice with regards to tissue oxygenation (5.16 ± 23.68 % vs. 10.93 ± 27.67 %, respectively, p=0.947). However, for the SV40 Tag mice, the animals with access to voluntary exercise showed mammary tissue more indicative of a hypoxic environment than the control group (-15.64 ± 30.95 % vs. 21.73 ± 27.10 %, respectively, p=0.061). Neither the FVB/NJ or SV40 Tag mice displayed any differences between the exercise or control subgroups when measuring perfusion using contrast-enhanced ultrasound. The WIR was greater for the FVB/NJ (p = 0.685) and SV40 Tag (p = 0.659) exercise groups than the control groups. Likewise, the AUC held a similar relationship between the two subgroups for the FVB/NJ (p = 0.073) and SV40 Tag (p = 0.523) mice. The higher WIR suggest higher vascularization in the exercise groups. Lastly, preliminary results did not support any significant differences between tumor sizes, although the control group did exhibit higher weekly tumor growth (p = 0.902). DCIS-like tumors were visibly seen in all mice at 12 weeks of age, while invasive cancer was indicative of the increasing weekly tumor size at weeks 15. Preliminary results show the potential for tissue oxygenation to be predictive precursor of DCIS progression. By predicting DCIS growth, the proper treatments can be determined to avoid the unnecessary physical, psychological, and financial costs caused by over diagnosis and overtreatments of DCIS.

Using a model system, the applicability of the frontal configuration of optoacoustic spectroscopy in analytical practice is shown. An optoacoustic cell made using layered-prism geometry was designed and tested; it ensures operation with a layer thickness of 20–100 μm and sample volumes of 50–100 μl. Conditions are proposed for determining iron(II) in the form of tris(1,10-phenanthrolinate) with the detection limit of 3 × 10−7 M, which is less that the detection limit under similar induction conditions and for the same determination procedure using thermal-lens spectrometry (4 × 10−7 M). The determination has high reproducibility (relative standard deviation for 10−6 M is 0.005) and expressivity (1 min per sample detection).

The cis -skew to trans -planar photoisomerization of benzil in the photoexcited state was studied by laser-induced optoacoustic spectroscopy (LIOAS) in a series of normal alkane solvents at room temperature. The structural volume change due to the photoisomerization process has been estimated and compared with the same calculated from the optimized skew and trans structures. The magnitude of the structural volume change is estimated to be 22.9 ± 1.2 mL/mol. This study reveals that an expansion in volume occurs during the photoinduced isomerization process. In non-polar alkane solvents, the estimated volume change has been argued to be free from electrostrictional contribution.

Background: Anemia is an underdiagnosed, significant public health concern afflicting >2 billion people worldwide. The detrimental effects of tissue oxygen deficiency on the cardiovascular system and concurrent appearance of anemia with numerous high-risk disorders highlight the importance of clinical screening. Currently there is no universally accepted, clinically applicable, noninvasive hemoglobin/hematocrit screening tool. The need for such a device has prompted an investigation into a breadth of techniques. Methods: A synopsis of the literature and current directions of research in noninvasive total hemoglobin measurement was collected. Contributions highlighted in this review are limited to those studies conducted with a clinical aspect, and most include in vivo patient studies. Results: The review of potential techniques presented here includes optoacoustic spectroscopy, spectrophotometric imaging, diffuse reflectance spectroscopy, transcutaneous illumination, electrical admittance plethysmography, and photoplethysmography. The technological performance, relative benefits of each approach, potential instrumentation design considerations, and future directions are discussed in each subcategory. Conclusions: Many techniques reviewed here have shown excellent accuracy, sensitivity, and specificity in measuring hemoglobin/hematocrit, thus in the near future a new clinically viable tool for noninvasive hemoglobin/hematocrit monitoring will likely be widely used for patient care. Limiting factors in clinical adoption will likely involve technology integration into the current standard of care in each field routinely dealing with anemia.

This chapter provides the molecular constants for (003) and (005) states of triatomic HD16O (H16OD) molecule measured using intracavity laser absorption spectroscopy, optoacoustic spectroscopy and theoretical calculation.

88 páginas. Doctorado en Ciencias e Ingeniería de Materiales. En el presente trabajo se planteó como objetivo general la obtención de las condiciones de depósito y la caracterización —por separado y conjuntamente— de las películas delgadas de ITO, BaTiO3, ZnO, ZnO:Mn, las cuales pueden dar lugar al desarrollo de una metodología para obtener celdas electroluminiscentes. Para esto, se realizaron varios juegos de películas delgadas por medio del depósito por láser pulsado (PLD), y para el caso particular del dopado, se empleó la variante de dos pulsos láser que inciden en distintos blancos, generando así el depósito de la película en conjunto con el dopado. En este punto es importante aclarar, que para la elaboración de la película delgada de ITO se utilizó otra técnica de depósito, ésta, conocida como erosión catódica. Cada una de las películas de ZnO y ZnO:Mn se caracterizaron por diferentes técnicas para identificar distintas propiedades. A continuación, se mencionan cada una de ellas. Rayos X: Se empleó para corroborar la cristalinidad de las películas delgadas, en donde cada película presentó una estructura tipo wurzita, orientada en los planos preferenciales (002) y (004). Perfilometria: Se midió el espesor de las películas, encontrando que todas se hallaban en el intervalo de 100 - 150 nm. EDS: Esta técnica se utilizó para conocer el porcentaje de incorporación del elemento dopante en la estructura de la película delgada. Debido a que se sabe que el depósito no es homogéneo al emplear PLD como método, se utilizó un diseño estadístico con la intensión de reducir al máximo la variabilidad. Se identificó una tendencia negativa en las películas, esto es, a mayor retraso entre láseres menor incorporación del elemento dopante. Para reconocer si las diferencias entre los promedios de incorporación eran estadísticamente significativos, se aplicó una prueba de hipótesis no paramétrica (debido a que los datos no seguían una distribución normal) y de comparaciones específicas. Fotoluminiscencia: Se realizó un barrido en el intervalo de longitud de onda de 350 - 400 nm a todas las películas delgadas, encontrado una influencia directa de la incorporación del elemento dopante respecto a la emisión de luz. Efecto Hall: Se midió la resistividad, movilidad y densidad de portadores de cada una de las películas delgadas, encontrado que éstas continuaron siendo semiconductoras independientemente del porcentaje de incorporación del elemento dopante. Espectroscopia UV - VIS: Por medio de esta técnica, se analizaron los espectros de absorción de cada una de las películas delgadas, encontrado que éste es constante en todo el intervalo. Fotoacústica: En la investigación, esta técnica de caracterización es la de mayor relevancia, ya que, a partir del empleo de la misma, es posible identificar cambios estructurales en las películas delgadas, aunque se encuentren en un porcentaje diminuto, como lo fue la detección de la fase blenda a 300 °C en las películas de ZnO, y la afectación de la incorporación del elemento dopante a dicha fase. La película delgada de BaTiO3 únicamente se caracterizó por medio de fotoacústica con la intención de localizar su temperatura de Curie, la cual se sabe se presenta a 110 °C, situación que se encontró al emplear la temperatura de 400 °C al realizar el depósito. Finalmente, se caracterizaron fotoacústicamente cada una de las multicapas que integran a la estructura electroluminiscente, esto, con la intención de conocer la influencia en los cambios estructurales al ir colocando película sobre película.

The electron-transfer reaction between the erythrosin dianion triplet, 3Er2-, and Mo(CN)84- was studied by laser-induced optoacoustic spectroscopy in the presence of various cations (Li+, Na+, K+, and Cs+, all at 4.4 × 10-2 M analytical concentration). The buffer was in each case the corresponding H3BO3/B(OH)4-,M+ (pH 9.18 at 20 °C). The enthalpy level of the triplet 3Er2- is ΔH1 = 180 ± 10 kJ mol-1 independent of the cation. The structural volume change for 3Er2- formation is ΔV1 = ca. 2 mL mol-1, attributed to intrinsic changes upon its formation. The formation of the redox products Er3- + Mo(CN)83- also leads to an expansion, ΔV2, between 12 mL mol-1 for Li+ and 8 mL mol-1 for Cs+, which linearly correlates with the heat released during the radical formation step. The correlation is interpreted in terms of an enthalpy−entropy compensation effect, due to the strong influence of the cations on the H-bond water network, also reflected in the correlation between ΔV2 and the literature values for the abilit...

We have developed an optoacoustic spectroscopy technique for noninvasive hematoma diagnostics and oxygenation monitoring with high resolution and accuracy. We will report results of our animal and clinical studies on these important applications.

Reaction volume changes, ΔVR, enthalpy content, ΔHMLCT, and decay lifetimes, τ2, of the metal-to-ligand charge transfer (MLCT) complex of (2,2‘-bipyridine)tetracyanoruthenate(II) complex, Ru(bpy)(CN)42-, inside the water pools of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles dispersed in n-alkanes, were determined using laser-induced optoacoustic spectroscopy (LIOAS). Emission quantum yields, Φem, of the complex were also determined by steady-state measurements. The enthalpy content of the MLCT state of Ru(bpy)(CN)42- was not dependent on the amount of water inside the reverse micelles (defined as the molar ratio R = [H2O]/[AOT]) and was, within experimental error, similar to that in water. However, the values of τ2 and Φem decrease while those of ΔVR increase as the values of R are incremented from 3 to 10. At the larger R values, τ2, Φem, and particularly ΔVR resemble the values in neat water. These results are interpreted to arise from the type of water involved in the hydrogen bond int...

Laser-induced optoacoustic spectroscopy (LIOAS) has been used for the quantitative analysis of pH and/or CO 2 in aqueous solutions. This technique implies the precise measurement of spectral variations of indicator dyes adsorbed on surfaces (e.g., polymer membranes). Optimization of the pH-sensitive membrane and of the sensor module leads to promising results due to the higher sensitivity of LIOAS in comparison with the conventional analysis by reflection spectroscopy.

Laser induced optoacoustic spectroscopy has been used to determine the relative contribution of the intersystem crossing and internal conversion to the non-radiative energy dissipation from the two excited ICT probes p-N,N-dimethylaminobenzonitrile (DMABN), and p-N,N-dimethylaminobenzaldehyde (DMABA) in solvents of different polarity. It is observed that while intersystem crossing is the main non-radiative deactivation process for DMABN in all the solvents studied this is not the case in polar solvents for DMABA.

A set of calorimetric references for excitation at λ = 266 nm in acetonitrile solutions is proposed. Theophylline and several purinic compounds (purine, 6-methylpurine, 6-methoxypurine, 6-chloropurine, and 6-aminopurine) were investigated using pulsed laser optoacoustic spectroscopy with resolution times between 150 ns and 1 μs and compared with 2-hydroxybenzophenone. At room temperature, all these compounds show no fluorescence, good stability and no photochemical processes as photodegradation or multiphotonic effects below fluences of 1000 J/m 2 .

It is important to identify patients with chronic obstructive pulmonary disease (COPD) and lung cancer in the early stages of the disease. The method of laser opto-acoustic gas analysis, in this case, can act as a promising tool for diagnostics. The material for this study were the gas emission samples collected from patients and healthy volunteers – samples of exhaled air, swabs from teeth and cheeks. A set of material was formed three groups: healthy volunteers, patients with COPD, lung cancer patients. The resulting samples were analyzed by means of laser opto-acoustic gas analyzers: with intracavity location detector (ILPA-1), with extracavity location detector (LGA-2). Presentation of the results in an easy to visual form was performed using the method of elastic maps, based on the principal component analysis. The results of analysis show potentialities of usage of laser optoacoustic spectroscopy application to assess the status of patients with chronic obstructive pulmonary disease and lung cancer.

An optoacoustic technique for solutions of strongly light-absorbing analytes at 0.1-0.01 mol l(-1) is proposed. The technique is based on the wide-band forward mode detection of temporal profiles of laser-generated ultrasonic pulses (optoacoustic signals). The leading edge of the signal repeats the distribution of the laser fluence in the medium, which makes it possible to determine its optical absorption and investigate its dynamics during a reaction. The range of light-absorption coefficients starts from 1 to 5 and reaches 10(4) to 10(5) cm(-1). The determination of iron(II) as ferroin shows the possibility of probing 0.1 mol l(-1) of iron(II), which was not previously achieved for this reaction by optical spectroscopy. To further prove the concept, kinetic measurements for ferroin decomposition at the level of 0.1 mol l(-1) and at high pHs are performed. The results are compared with spectrophotometry at lower concentrations and show good reproducibility and accuracy of kinetic constants.

Hummers method is commonly used for the fabrication of graphene oxide (GO) from graphite particles. The oxidation process also leads to the cutting of graphene sheets into small pieces. From a thermodynamic perspective, it seems improbable that the aggressive, somewhat random oxidative cutting process could directly result in graphene nanosheets without destroying the intrinsic π-conjugated structures and the associated exotic properties of graphene. In Hummers method, both KMnO4 and NO2(+) (nitronium ions) in concentrated H2SO4 solutions act as oxidants via different oxidation mechanisms. From both experimental observations and theoretical calculations, it appears that KMnO4 plays a major role in the observed oxidative cutting and unzipping processes. We find that KMnO4 also limits nitronium oxidative etching of graphene basal planes, therefore slowing down graphene fracturing processes for nanosheet fabrication. By intentionally excluding KMnO4 and exploiting pure nitronium ion oxidation, aided by the unique thermal and kinetic effects induced by microwave heating, we find that graphite particles can be converted into graphene nanosheets with their π-conjugated aromatic structures and properties largely retained. Without the need of any postreduction processes to remove the high concentration of oxygenated groups that results from Hummers GO formation, the graphene nanosheets as-fabricated exhibit strong absorption, which is nearly wavelength-independent in the visible and near-infrared (NIR) regions, an optical property typical for intrinsic graphene sheets. For the first time, we demonstrate that strong photoacoustic signals can be generated from these graphene nanosheets with NIR excitation. The photo-to-acoustic conversion is weakly dependent on the wavelength of the NIR excitation, which is different from all other NIR photoacoustic contrast agents previously reported.

We have developed an optoacoustic technique for noninvasive cerebral and central venous oxygenation monitoring. Our data indicate that optoacoustics can provide noninvasive, accurate, continuous monitoring of cerebral and central venous oxygenation.