Exploring the nanoscale: AFM-IR visualization of cysteine adsorption on gold nanoparticles.

This study focuses on the adsorption process of L-cysteine (Cys), a sulfur-containing amino acid, onto monolayers of gold nanoparticles (AuNPs) prepared through distinct protocols on mica substrates. Two types of AuNPs were prepared using two different methods: the first employed a physical approach, which combined the Inert Gas Condensation (IGC) technique with the magnetron sputtering method, while the second utilized a chemical method involving the reduction of tetrachloroauric acid with trisodium citrate (TC). The characterization of AuNPs was performed using transmission electron microscopy (TEM) and atomic force microscopy (AFM), of up to 5 ± 1.3 nm for bare AuNPs obtained through vacuum techniques, and up to 12 ± 5 nm for negatively charged, citrate-stabilized TCAuNPs(-). The application of spectroscopic techniques based on the surface-enhanced effects allows for describing the adsorption process in both micro- and nanoscale systems: Cys/bare AuNPs and Cys/ TCAuNPs(-). The commonly used surface-enhanced Raman spectroscopy (SERS) technique provided insights into adsorption behaviours at the microscale level. In the case of TCAuNPs(-), an interaction involving the lone electron pair of sulfur (S) atom and metal surface, while on the bare AuNPs, S is adsorbed on the surface, but the cleavage of the SH group is not discernible. Nanoscale analysis was complemented using AFM combined with the surface-enhanced infrared absorption spectroscopy (AFM-SEIRA) technique. AFM-SEIRA map indicated the formation of hot spot which were predominantly located between aggregated TCAuNPs(-) and on specific NPs surfaces (area between NPs and gold-coated tip). Results from the SERS and AFM-SEIRA techniques were in good agreement, underscoring the comprehensive understanding achieved through the chosen experimental approach regarding the Cys interactions with layers of AuNPs.

Quantitative and qualitative analyses of drug adsorption on silver nanoparticle monolayers: QCM, SERS, and TEIRA nanospectroscopy studies.

In this study for the first time, surface-enhanced Raman spectroscopy (SERS) and tip-enhanced infrared (TEIRA) nanospectrocopy together with a quartz crystal microbalance (QCM) are postulated as powerful tools for comprehensive qualitative and quantitative analyses of drug/metal nanocarrier conjugates. The development of efficient drug/carrier systems requires that the stability of the drug/carrier connection be estimated and the number of drug molecules immobilized on the carrier surface be determined. Thus, such a characterization study is highly desirable. Here, the SERS technique was applied to identify how erlotinib, a drug applied in non-small cell lung cancer (NSCLC) therapy, interacts with silver nanoparticles (AgNPs) that are considered as drug carriers. These investigations indicate that in the erlotinib/AgNP suspension, the drug strongly connects with the NPs mainly through the phenylacetylene moiety. The QCM was used to prepare an AgNP monolayer with a monitored degree of coverage and to perform controlled erlotinib adsorption as a next step. The results indicate that the drug forms a stable layer on the AgNP monolayer and also show the amount of the erlotinib molecules which underwent immobilization on the metal nanosurface. Simultaneously, it was identified how the erlotinib layer adsorbs on the AgNP monolayer using TEIRA nanospectroscopy with ultra-high spatial resolution. The obtained results show that the phenylacetylene, ethoxy, and methoxy moieties are mainly responsible for the drug/AgNP monolayer connection. Additionally, the performed studies also try to explain the surface-enhanced phenomena that occur during the TEIRA experiments and attempt to prove the statement that the "tip-enhanced" effect plays a crucial role in the detection of the thin erlotinib layer deposited on the AgNP monolayer.

Carotenoids contribution in rapid diagnosis of multiple sclerosis by Raman spectroscopy.

Rapid and accurate diagnosis of any illness determines the success of treatment. The same applies to multiple sclerosis (MS), chronic, inflammatory, and neurodegenerative diseases (ND) of the central nervous system (CNS). Unfortunately, the definitive diagnosis of MS is prolonged and involves mainly clinical symptoms observation and magnetic resonance imaging (MRI) of the CNS. However, as we previously reported, Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy shed new light on the minimally invasive, label-free, and rapid diagnosis of this illness through blood fraction. Herein we introduce Raman spectroscopy coupled with chemometric analysis to provide more detailed information about the biochemical changes behind MS. This pilot study demonstrates that mentioned combination may provide a new diagnostic biomarker and bring closer to rapid MS diagnosis. It has been shown that Raman spectroscopy provides lipid and carotenoid molecules as useful biomarkers which may be applied for both diagnosis and treatment monitoring.

Spectral signature of multiple sclerosis. Preliminary studies of blood fraction by ATR FTIR technique.

Multiple sclerosis (MS) is a chronic, neurodegenerative disease of central nervous system, characterized by inflammation, demyelination, and gliosis. It is commonly known the rapid and accurate diagnosis of MS determines treatment success. The standard diagnosis contains clinical symptoms observation, magnetic resonance imaging (MRI) of central nervous system (CNS), and analysis of cerebrospinal fluid (CSF). Nonetheless, since CSF sampling is considered invasive and not all individuals are eligible for MRI we have decided to propose other diagnostic tool such as spectroscopy. Unlike lumbar puncture, blood collection is a routine procedure regarded as low-invasive; therefore, we used Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy. This technique was combined with chemometrics and detailed spectral assay to analyse blood plasma and serum samples collected from MS patients and healthy individuals. The results revealed a clear identification pattern of MS, suggesting the conformation changes of amide III collagen-like proteins in plasma and the dominance of amide I ß-sheet structures. Those changes in serum spectra seem to be useful for sample differentiation.

Surface Functionalization of Poly(l-lactide-co-glycolide) Membranes with RGD-Grafted Poly(2-oxazoline) for Periodontal Tissue Engineering.

Bone tissue defects resulting from periodontal disease are often treated using guided tissue regeneration (GTR). The barrier membranes utilized here should prevent soft tissue infiltration into the bony defect and simultaneously support bone regeneration. In this study, we designed a degradable poly(l-lactide-co-glycolide) (PLGA) membrane that was surface-modified with cell adhesive arginine-glycine-aspartic acid (RGD) motifs. For a novel method of membrane manufacture, the RGD motifs were coupled with the non-ionic amphiphilic polymer poly(2-oxazoline) (POx). The RGD-containing membranes were then prepared by solvent casting of PLGA, POx coupled with RGD (POx_RGD), and poly(ethylene glycol) (PEG) solution in methylene chloride (DCM), followed by DCM evaporation and PEG leaching. Successful coupling of RGD to POx was confirmed spectroscopically by Raman, Fourier transform infrared in attenuated reflection mode (FTIR-ATR), and X-ray photoelectron (XPS) spectroscopy, while successful immobilization of POx_RGD on the membrane surface was confirmed by XPS and FTIR-ATR. The resulting membranes had an asymmetric microstructure, as shown by scanning electron microscopy (SEM), where the glass-cured surface was more porous and had a higher surface area then the air-cured surface. The higher porosity should support bone tissue regeneration, while the air-cured side is more suited to preventing soft tissue infiltration. The behavior of osteoblast-like cells on PLGA membranes modified with POx_RGD was compared to cell behavior on PLGA foil, non-modified PLGA membranes, or PLGA membranes modified only with POx. For this, MG-63 cells were cultured for 4, 24, and 96 h on the membranes and analyzed by metabolic activity tests, live/dead staining, and fluorescent staining of actin fibers. The results showed bone cell adhesion, proliferation, and viability to be the highest on membranes modified with POx_RGD, making them possible candidates for GTR applications in periodontology and in bone tissue engineering.

Design cytotoxicity: The effect of silver nanoparticles stabilized by selected antioxidants on melanoma cells.

Silver nanoparticles (AgNPs) prepared and stabilized by diverse biologically active substances seem to be especially useful in diverse biological and medical applications. The combination of AgNPs with bioactive substances, such as antioxidants, can lead to the development of new systems of desired anticancer properties. In this research, AgNPs were prepared with the use of diverse antioxidant combinations including gallic acid (GA), (-)-epicatechin-3-gallate (EGCG), and caffeine (CAF). The insightful physicochemical characteristic revealed that each type of AgNPs exhibited spherical shape, comparable size distribution and negative surface charge. Surface-enhanced Raman spectroscopy (SERS) delivered the information about the chemistry of AgNP stabilizing layers, which turned out to be a crucial factor tuning toxicity of AgNPs toward murine B16 melanoma cells (B16-F0) and human skin melanoma (COLO 679) cells. EGCGAgNPs were the most cytotoxic among all the investigated AgNPs. They strongly reduced the activity of mitochondria, damaged cell membrane integrity, and penetrated inside the cells causing DNA damage. In turn, the toxicity of GAAgNPs strongly manifested via the induction of oxidative stress in the cells. It was found that CAFGAAgNPs exhibited the lowest toxicity toward the melanoma cells, which proved that a proper combination of antioxidants enable to prepare AgNPs of differentiated toxicity. It was established that human skin melanoma cells were significantly more sensitive to AgNPs than the murine melanoma cells.

Tracking of the biochemical changes upon pleomorphic adenoma progression using vibrational microspectroscopy.

Head and neck tumors can be very challenging to treat because of the risk of problems or complications after surgery. Therefore, prompt and accurate diagnosis is extremely important to drive appropriate treatment decisions, which may reduce the chance of recurrence. This paper presents the original research exploring the feasibility of Fourier transform infrared (FT-IR) and Raman spectroscopy (RS) methods to investigate biochemical alterations upon the development of the pleomorphic adenoma. Principal component analysis (PCA) was used for a detailed assessment of the observed changes and to determine the spectroscopic basis for salivary gland neoplastic pathogenesis. It is implied that within the healthy margin, as opposed to the tumoral tissue, there are parts that differ significantly in lipid content. This observation shed new light on the crucial role of lipids in tissue physiology and tumorigenesis. Thus, a novel approach that eliminates the influence of lipids on the elucidation of biochemical changes is proposed. The performed analysis suggests that the highly heterogeneous healthy margin contains more unsaturated triacylglycerols, while the tumoral section is rich in proteins. The difference in protein content was also observed for these two tissue types, i.e. the healthy tissue possesses more proteins in the anti-parallel ß-sheet conformation, whereas the tumoral tissue is dominated by proteins rich in unordered random coils. Furthermore, the pathogenic tissue shows a higher content of carbohydrates and reveals noticeable differences in nucleic acid content. Finally, FT-IR and Raman spectroscopy methods were proposed as very promising methods in the discrimination of tumoral and healthy tissues of the salivary gland.

Antioxidant-modulated cytotoxicity of silver nanoparticles.

The properties of silver nanoparticles (AgNPs) synthesized using compounds exhibiting biological activity seem to constitute an interesting issue worthy of examination. In these studies, two types of AgNPs were synthesized by a chemical reduction method using well-known antioxidants: gallic acid (GA) and ascorbic acid (AA). Transmission electron microscopy (TEM) and atomic force microscopy (AFM) revealed that the AgNPs were spherical. The average size was equal to 26 ± 6 nm and 20 ± 7 nm in the case of ascorbic acid-silver nanoparticles (AAgNPs) and gallic acid-silver nanoparticles (GAAgNPs), respectively. Surface-enhanced Raman spectroscopy (SERS) confirmed that the AgNPs were not stabilized by pure forms of applied antioxidants. Changes in mitochondrial activity and secretion of inflammatory and apoptosis mediators after the exposure of human promyelocytic (HL-60) and histiocytic lymphoma (U-937) cells to the AgNPs were studied to determine the impact of stabilizing layers on nanoparticle toxicity. The GAAgNPs were found to be more toxic for the cells than the AAgNPs. Their toxicity was manifested by a strong reduction in mitochondrial activity and induction of the secretion of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and caspase-9. The addition of pure antioxidants to the AgNP suspensions was found to influence their toxicity. There was a significant positive effect in the case of the mixture of AA with AAgNPs and GA with GAAgNPs. The results obtained suggest that the presence of stabilizing agents adsorbed on the surface of AgNPs is the main factor in shaping their toxicity. Nevertheless, the toxic effect can be also tuned by the introduction of free antioxidant molecules to the AgNP suspensions.

The Impact of Preprocessing Methods for a Successful Prostate Cell Lines Discrimination Using Partial Least Squares Regression and Discriminant Analysis Based on Fourier Transform Infrared Imaging.

Fourier transform infrared spectroscopy (FT-IR) is widely used in the analysis of the chemical composition of biological materials and has the potential to reveal new aspects of the molecular basis of diseases, including different types of cancer. The potential of FT-IR in cancer research lies in its capability of monitoring the biochemical status of cells, which undergo malignant transformation and further examination of spectral features that differentiate normal and cancerous ones using proper mathematical approaches. Such examination can be performed with the use of chemometric tools, such as partial least squares discriminant analysis (PLS-DA) classification and partial least squares regression (PLSR), and proper application of preprocessing methods and their correct sequence is crucial for success. Here, we performed a comparison of several state-of-the-art methods commonly used in infrared biospectroscopy (denoising, baseline correction, and normalization) with the addition of methods not previously used in infrared biospectroscopy classification problems: Mie extinction extended multiplicative signal correction, Eiler's smoothing, and probabilistic quotient normalization. We compared all of these approaches and their effect on the data structure, classification, and regression capability on experimental FT-IR spectra collected from five different prostate normal and cancerous cell lines. Additionally, we tested the influence of added spectral noise. Overall, we concluded that in the case of the data analyzed here, the biggest impact on data structure and performance of PLS-DA and PLSR was caused by the baseline correction; therefore, much attention should be given, especially to this step of data preprocessing.

In search of the correlation between nanomechanical and biomolecular properties of prostate cancer cells with different metastatic potential.

Nanomechanical properties of living cells, as measured with atomic force microscopy (AFM), are increasingly recognized as criteria that differentiate normal and pathologically altered cells. Locally measured cell elastic properties, described by the parameter known as Young's modulus, are currently proposed as a new diagnostic parameter that can be used at the early stage of cancer detection. In this study, local mechanical properties of normal human prostate (RWPE-1) cells and a range of malignant (22Rv1) and metastatic prostate cells (LNCaP, Du145 and PC3) were investigated. It was found that non-malignant prostate cells are stiffer than cancer cells while the metastatic cells are much softer than malignant cells from the primary tumor site. Next, the biochemical properties of the cells were measured using confocal Raman (RS) and Fourier-transform infrared (FT-IR) spectroscopies to reveal these cells' biochemical composition as malignant transformation proceeds. Nanomechanical and biochemical profiles of five different prostate cell lines were subsequently analyzed using partial least squares regression (PLSR) in order to identify which spectral features of the RS and FT-IR spectra correlate with the cell's elastic properties. The PLSR-based model could predict Young's modulus values based on both RS and FT-IR spectral information. These outcomes show not only that AFM, RS and FT-IR techniques can be used for discrimination between normal and cancer cells, but also that a linear correlation between mechanical response and biomolecular composition of the cells that undergo malignant transformation can be found. This knowledge broadens our understanding of how prostate cancer cells evolve thorough the multistep process of tumor pathogenesis.

Micro- and Nanoscale Spectroscopic Investigations of Threonine Influence on the Corrosion Process of the Modified Fe Surface by Cu Nanoparticles.

The work presents a comprehensive vibrational analysis of the process of adsorption of threonine (Thr) onto an Fe surface with deposited Cu nanoparticles (NPs) (of about 4-5 nm in size) in a corrosive environment. The application of surface-enhanced Raman spectroscopy (SERS) and surface-enhanced infrared absorption spectroscopy (SEIRA) provides the opportunity for detailed description of adsorption geometry of amino acid onto a metal surface. The combination of conventional infrared spectroscopy (IR) with atomic force microscopy (AFM) resulted in a nano-SEIRA technique which made it possible to provide a precise description of adsorbate binding to the metal surface. The studies presented confirmed that there is a very good correlation between the spectra recorded by the SERS, SEIRA, and nano-SEIRA techniques. Threonine significantly influenced the process of corrosion of the investigated surface due to the existing strong interaction between the protonated amine and carboxylate groups and the CuNPs deposited onto the Fe surface. In addition, the application of two polarization modulations (s and p) in nano-SEIRA allows subtle changes to be observed in the molecule geometry upon adsorption, with the carboxylate group of Thr being almost horizontally oriented onto the metal surface; whereas the amine group that contains nitrogen is oriented perpendicular to this surface.

Nanoscale infrared probing of amyloid formation within the pleomorphic adenoma tissue.

BACKGROUND: The process of malignant transformations of many tumour cases is still unclear and more specific experimental approaches are necessary. The detailed identification of the pathological changes may help in the therapy progression through the development of drugs with more selective action. METHODS: In this study, the AFM-IR nanospectroscopy was applied for the first time to the pleomorphic adenoma (TM) and the marginal tissue characterizations. In order to verify the obtained spectral information, conventional FT-IR investigations were also performed. RESULTS: The AFM-IR data (topographies, intensity maps, and spectra) show structural changes observed for the margin and TM samples. Additionally, within the tumour tissue the fibril-like areas, characteristic for amyloid diseases, were distinguished. CONCLUSIONS: The application of AFM-IR allows to determine changes in the protein secondary structures between the fibrils and the regions outside them. It has been proved that, for the former areas, the α-helix/random coil/ ß-sheet components dominate, while for the latter regions the α-helix/random coil indicate the main contribution to the protein composition. GENERAL SIGNIFICANCE: The FT-IR results remain in good agreement with the AFM-IR data recorded for the areas outside the fibrils of the TM. This observation confirms that by means of the conventional FT-IR method the identification of the considered fibrils structure would be impossible. Only application of the AFM-IR nanospectroscopy allow for characterization and visualization of the fibrillization process occurring within the investigated tumour tissue.

Spectroscopic insights into the effect of pH, temperature, and stabilizer on erlotinib adsorption behavior onto Ag nanosurface.

In this study, surface - enhanced Raman spectroscopy (SERS) was applied at the first time for estimation of how pH, temperature, and nanoparticle (NP) stabilizer affect an adsorption behavior of erlotinib (drug approved in a non-small cell lung cancer therapy) onto citrate-stabilized silver nanoparticles (AgNPs). Novel approach to improve cancer therapy assumes application of NPs as an efficient drug delivery system. This strategy requires designing stable drug/nanocarrier conjugates that can effectively interact in the target site. It is also important to perform deeply characterization of a drug orientation on the potential carrier surface and estimation how stable the appeared interaction is. Performed analysis, indicates that pH, temperature, presence of NP stabilizers, and time of incubation have an influence on the occurring adsorption geometry of the drug. However, the observed erlotinib/AgNP interaction remains stable regardless of the applied conditions. These considerations were supported by insightful physicochemical characteristics of the AgNPs and the erlotinib/AgNP conjugates by conducting transmission electron microscopy (TEM) imaging, determination of colloid stability conducted with the use of dynamic light scattering technique (DLS) and measurements of electrophoretic mobility. Such complex approach allows a better understanding of the stability of the erlotinib/AgNP conjugates and provides information how the investigated interaction is affected by the induced perturbations.

Characterization of the Brain Penetrant Neuropeptide Y Y2 Receptor Antagonist SF-11.

This paper discusses the biological and three-dimensional molecular structure of the novel, nonpeptide Y2R antagonist, SF-11 [N-(4-ethoxyphenyl)-4-(hydroxydiphenylmethyl)-1-piperidinecarbothioamide]. Pharmacokinetic studies in a rat model indicated that, following intraperitoneal dosing, SF-11 crossed the blood-brain barrier and was able to penetrate the brain, making it a suitable tool for behavioral studies. We showed for the first time that SF-11 decreased the immobility time in the forced swim test (FST) after acute peripheral administration (10 and 20 mg/kg), indicating that it has antidepressant potential. Inhibitors of the mitogen-activated protein kinase/extracellular signal regulated kinase (MAPK/ERK) and phosphatidylinositol 3-kinase (PI3K) signaling pathways blocked the anti-immobility effect of SF-11, suggesting that these pathways are involved in the antidepressant-like activity of SF-11 in the FST. The results of locomotor activity of rats indicate that the effects observed in the FST are specific and due to the antidepressant-like activity of SF-11. These findings provide further evidence for the antidepressant potential of Y2R antagonists. Also, the application of Fourier transform infrared absorption (FT-IR) and Raman spectroscopy (RS) methods combined with theoretical density functional theory (DFT) calculations allowed us to present the optimized spatial orientation of the investigated drug. Structural characterization of SF-11 based on vibrational spectroscopic data is of great importance and will aid in understanding its biological activity and pave the way for its development as a new antidepressant agent.

Erythrocyte heme­oxygenation status indicated as a risk factor in prehypertension by Raman spectroscopy.

Raman spectroscopy of erythrocytes provides detailed information about the structure and status of heme moiety, which can be used to provide new insights into molecular pathogenesis of several diseases. In this study, we present the first Raman spectroscopy investigations of the effect of hemoglobin oxygenation in the context of hypertensive disease. The experimental data was subjected to Logistic Regression, which indicated heme­oxygenation status as an important risk factor alongside other clinical parameters. The 1605/1621 cm-1 band ratio was selected as an optimal Raman metric for risk assessment and along with other band ratios (1583, 1639, 1310 cm-1) related to heme status and when combined with clinical data via logistic regression gave an Area Under the Curve (AUC) >0.95 for prehypertension risk prediction. The work demonstrates the feasibility of Raman spectroscopy to distinguish between prehypertensive and normotensive states. Simultaneously, it is implied that the etiology of the high blood pressure progression may be connected with the changes in hemoglobin oxygenation.

Triglycerides as indicators of erythrocyte hemoglobin oxygen-binding properties1.

OBJECTIVES: To assess the relationships of clinical and laboratory parameters, with erythrocyte oxygen concentration. METHODS: The study group consisted of 47 healthy adults out of which 16 showed slightly higher blood pressure and were classified as individuals with prehypertension. For each individual, data were obtained on: systolic and diastolic blood pressure (SBP, DBP), blood morphology, lipids profile, fibrinogen, hs-CRP. The erythrocyte oxygen concentration was assessed with the Raman spectroscopy technique. Arithmetic means for all laboratory parameters were estimated by oxygen concentration tertiles and tested for statistical significance of linear trends across tertiles. RESULTS: The multivariate regression analysis showed statistically significant negative relationship of triglycerides level with oxygen concentration. CONCLUSIONS: A hypothesis has been formulated that triglycerides level is an indicator of the erythrocyte ability to transport oxygen to the tissues.

SERS characterization of neuropeptide Y and its C-terminal fragments deposited onto colloidal gold nanoparticle surface.

It has been suggested that the family of neuropeptide Y (NPY) peptides is a promising target for the neuroprotective therapy; therefore, knowledge of the structure of these biologically active compounds and their behavior at solid/liquid interface is important in order to design new analogues. Because there is still a lack of detailed information on the behavior of NPY and its mutated analogues at the solid/liquid interfaces, in this work surface-enhanced Raman spectroscopy (SERS) analysis was used to investigate NPY and its native NPY3-36, NPY13-36, and NPY22-36 and mutated acetyl-(Leu28,31)-NPY24-36C-terminal fragments, acting on Y2 receptors (Y2R), in order to determine their possible metal surface/molecule interactions. In these studies, colloidal gold nanoparticle surface served as a solid surface, whereas an aqueous solution was used as a liquid medium. The observed differences in the band intensities, wavenumbers, and widths allowed us to draw conclusions on an adsorption mode of NPY and on changes in this mode upon the shortening of the peptide chain and increase in solution pH (from pH 3 to pH 11). Briefly, three different species of Tyr were identified onto the colloidal gold surface depending upon the length of the peptide chain and solution pH. Tyrosine (TyrOH) is present in a basic medium. Tyrosinate (TyrO-) is present in an acidic solution, whereas phenoxyl radical (Tyr*) appears at neutral pH for peptides having relatively short peptide chain (acetyl-(Leu28,31)-NPY24-36). The elongation of the peptide chain partially (NPY13-36 and NPY22-36) or completely (NPY3-36 and NPY) protects the Tyr residue against conversion to the radical form.

Neuropeptide Y and its C-terminal fragments acting on Y2 receptor: Raman and SERS spectroscopy studies.

In this paper, we present spectroscopic studies of neuropeptide Y (NPY) and its native NPY(3-36), NPY(13-36), and NPY(22-36) and mutated acetyl-(Leu(28,31))-NPY(24-36)C-terminal fragments acting on Y2 receptor. Since there is some evidence for the correlation between the SERS patterns and the receptor binding ability, we performed a detailed analysis for these compounds at the metal/water interface using Raman spectroscopy (RS) and surface-enhanced Raman spectroscopy (SERS) methods. Many studies have suggested that interactions of this kind are crucial for a variety of biomedical and biochemical phenomena. The identification of amino acids in these peptide sequences by SERS allowed us to determine which molecular fragments were responsible for the interaction with the silver nanoparticle surface. Our findings demonstrated that in all of the investigated compounds, the NPY(32-36)C-terminal fragment (Thr(32)-Arg(33)-Gln(34)-Arg(35)-Tyr(36)NH2) was involved in the adsorption process onto metal substrate. The results of the present study suggest that the same molecular fragment interacts with the Y2 receptor, what proved the usefulness of the SERS method in the study of these biologically active compounds. The search for analogs acting on Y2 receptor may be important from the viewpoint of possible future clinical applications.

Influence of substituent type and position on the adsorption mechanism of phenylboronic acids: infrared, Raman, and surface-enhanced Raman spectroscopy studies.

This paper shows systematic spectroscopic studies using Fourier-transform infrared absorption (FT-IR), Fourier-transform Raman (FT-Raman), and surface-enhanced Raman (SERS) in an aqueous silver sol of fluoro and formyl analogues of phenylboronic acids: 2-fluorophenylboronic acid (2-F-PhB(OH)2), 3-fluorophenylboronic acid (3-F-PhB(OH)2), 4-fluorophenylboronic acid (4-F-PhB(OH)2), 2-formylphenylboronic acid (2-CHO-PhB(OH)2), 3-formylphenylboronic acid (3-CHO-PhB(OH)2), and 4-formylphenylboronic acid (4-CHO-PhB(OH)2). To produce an extensive table of vibrational spectra, density functional theory (DFT) calculations with the B3LYP method at the 6-311++G(d,p) level of theory were performed for the ground state geometry of the most stable species, dimers in cis-trans conformation. On the basis of the SERS spectral profile, the adsorption modes of the phenylboronic acid isomers were proposed. The type of substituent and its position in the phenyl ring have a strong influence on the geometry of isomers on the silver nanoparticle's surface. This effect was especially evident in the case of 4-CH-PhB(OH)2, for which dearomatization of the phenyl ring took place upon adsorption.

Vibrational and theoretical studies of the structure and adsorption mode of m-nitrophenyl α-guanidinomethylphosphonic acid analogues on silver surfaces.

This work presents Fourier transform Raman (FT-Raman), Fourier transform absorption infrared (FT-IR), and surface-enhanced Raman scattering (SERS) spectroscopic investigations of three m-nitrophenyl α-guanidinomethylphonic acids, including m-NO2PhG(cHex)P, m-NO2PhG(Morf)P, and m-NO2PhG(An)P, adsorbed onto colloidal and roughened silver surfaces. The SERS spectra were deconvoluted to determine the overlapped bands from which the specific molecular orientation can be deducted. The vibrational wavenumbers are calculated through density functional theory (DFT) at the B3LYP/6-31++G** level with the Gaussian 03, Raint, GaussSum 0.8, and GAR2PED software packages. The experimental and calculated vibrational bands are compared to those from SERS for the investigated compounds adsorbed on colloidal and roughened silver surfaces. The geometry of these molecules on the SERS-active silver surfaces is deduced from the observed changes in both the intensity and width of the Raman bands in the spectra of the bound species relative to the free species.