Ag-decorated polymer chip for the determination of the respective concentrations of TTD and Hg2+ by surface-enhanced raman scattering.

A "hotspot"-rich Ag-nanoparticle-decorated three-dimensional polymer substrate was fabricated, exhibiting an excellent surface-enhanced Raman scattering (SERS) activity. 4-Mercaptobenzoic acid (MBA) was selected as a probe molecule for comparing the SERS activity on selected substrates. The proposed detection chip with the adsorption of tetramethylthiuram disulfide (TTD) shows an excellent sensitivity for the quantitative determination of TTD and mercury ions (Hg2+). This chip exhibited a high sensitivity for the trace detection of the targets. Interestingly, we found that the adsorbed TTD is selectively sensitive to Hg2+. The SERS band had a significant frequency shift of 11 cm-1 as the concentration of Hg2+ increased from 10-10 to 10-3 mol L-1. More importantly, the frequency shift of the SERS band exhibited an excellent linear relationship with the concentration of Hg2+, and the determination limit for Hg2+ was 10-10 mol L-1. Furthermore, the proposed detection chip shows great application potential for the determination of pesticides and Hg2+.

Different Molecular Interaction between Collagen and α- or ß-Chitin in Mechanically Improved Electrospun Composite.

Although collagens from vertebrates are mainly used in regenerative medicine, the most elusive issue in the collagen-based biomedical scaffolds is its insufficient mechanical strength. To solve this problem, electrospun collagen composites with chitins were prepared and molecular interactions which are the cause of the mechanical improvement in the composites were investigated by two-dimensional correlation spectroscopy (2DCOS). The electrospun collagen is composed of two kinds of polymorphs, α- and ß-chitin, showing different mechanical enhancement and molecular interactions due to different inherent configurations in the crystal structure, resulting in solvent and polymer susceptibility. The collagen/α-chitin has two distinctive phases in the composite, but ß-chitin composite has a relatively homogeneous phase. The ß-chitin composite showed better tensile strength with ~41% and ~14% higher strength compared to collagen and α-chitin composites, respectively, due to a favorable secondary interaction, i.e., inter- rather than intra-molecular hydrogen bonds. The revealed molecular interaction indicates that ß-chitin prefers to form inter-molecular hydrogen bonds with collagen by rearranging their uncrumpled crystalline regions, unlike α-chitin.

Continuing progress in the field of two-dimensional correlation spectroscopy (2D-COS): Part III. Versatile applications.

In this review, the comprehensive summary of two-dimensional correlation spectroscopy (2D-COS) for the last two years is covered. The remarkable applications of 2D-COS in diverse fields using many types of probes and perturbations for the last two years are highlighted. IR spectroscopy is still the most popular probe in 2D-COS during the last two years. Applications in fluorescence and Raman spectroscopy are also very popularly used. In the external perturbations applied in 2D-COS, variations in concentration, pH, and relative compositions are dramatically increased during the last two years. Temperature is still the most used effect, but it is slightly decreased compared to two years ago. 2D-COS has been applied to diverse systems, such as environments, natural products, polymers, food, proteins and peptides, solutions, mixtures, nano materials, pharmaceuticals, and others. Especially, biological and environmental applications have significantly emerged. This survey review paper shows that 2D-COS is an actively evolving and expanding field.

Evaluation of SERS activity for cosputtered Ag-ZnX@PS (X = O, S, Se) composites: Carrier density dependence.

Ag-ZnX (X = O, S, Se) composites coated on polystyrene (PS) arrays (Ag-ZnO@PS, Ag-ZnS@PS, Ag-ZnSe@PS) were successfully fabricated by using cosputtering technology. We found that ZnX doping decreased the carrier densities of these composites compared to that of pure Ag@PS, which was due to redistribution of electrons between Ag and ZnX. Thus, the carrier density of Ag was decreased, and the surface plasmon resonance (SPR) of Ag was redshifted in the Ag-ZnX composites. As the redshift of the SPR of Ag induced a high SPR contribution to the surface-enhanced Raman scattering (SERS), the SPR and charge transfer (CT) contributions were simultaneously increased with increasing carrier density in the Ag-ZnX composites. This study opens a new path to designing metal-semiconductor composites with controllable carrier density. Regulation of the carrier density will be of great help in understanding SPR and CT contributions.

Dual irradiation-triggered anticancer therapeutics composed of polydopamine-coated gold nanoparticles.

The therapeutic efficacy of nanoparticles depends on their ability to release encapsulated photosensitizers. Here, surface-engineered metallic gold nanoparticles (AuNP) were irradiated with dual near-infrared (NIR) light to enhance the release of photosensitizer. Dopamine hydrochloride was surface-polymerized to polydopamine (PDA) layers on AuNP, and chlorin-e6 (Ce6) was chemically tethered to primary amines of PDA. The resulting Ce6-conjugated AuNP were characterized by Raman and X-ray photoelectron spectroscopy and visualized by electron microscopy and light scattering. The generation of reactive oxygen species was increased following dual NIR irradiation at 650 nm and 808 nm, which was attributed to the increased liberation of Ce6. In vitro, dual NIR irradiation significantly enhanced the anticancer effect of Ce6-incorporating AuNP by increasing the population of apoptotic cells. In vivo, tumor xenografted animals exhibited much better tumor suppression when subjected to dual NIR irradiation. Thus, we propose the use of Ce6-incorporating AuNP coupled to dual NIR irradiation for future anticancer treatment of solid tumors.

Atom transfer radical-polymerized cationic shells on gold nanoparticles for near infrared-triggered photodynamic therapy of tumor-bearing animals.

Gold nanoparticles (AuNPs) were surface-engineered with a cationic corona to enhance the incorporation of photosensitizers for photodynamic therapy (PDT). The cationic corona composed of poly(2-(dimethylamino)ethyl methacrylate) was atom transfer radical-polymerized on the surface of the AuNPs. The cationic corona of the engineered surface was characterized by dynamic light scattering, electron microscopy, Raman spectroscopy, and mass spectroscopy. Chlorin-e6 (Ce6) incorporated onto the surface-engineered AuNPs exhibited higher cell incorporation efficiency than bare AuNPs. Ce6-incorporated AuNPs were confirmed to release singlet oxygen upon NIR irradiation. Compared to Ce6, Ce6-incorporated AuNPs exhibited higher cellular uptake and cytotoxicity against cancer cells in an irradiation time-dependent manner. Near-infrared-irradiated animals administered Ce6-incorporated AuNPs exhibited higher levels of tumor suppression without noticeable body weight loss. This result was attributed to the higher localization of Ce6 at the tumor sites to induce cancer cell apoptosis. Thus, we envision that engineered AuNPs with cationic corona can be tailored to effectively deliver photosensitizers to tumor sites for photodynamic therapy.

Comparison Study of the Effects of Cationic Liposomes on Delivery across 3D Skin Tissue and Whitening Effects in Pigmented 3D Skin.

Charged phospholipids are employed to formulate liposomes with different surface charges to enhance the permeation of active ingredients through epidermal layers. Although 3D skin tissue is widely employed as an alternative to permeation studies using animal skin, only a small number of studies have compared the difference between these skin models. Liposomal delivery strategies are investigated herein, through 3D skin tissue based on their surface charges. Cationic, anionic, and neutral liposomes are formulated and their size, zeta-potential, and morphology are characterized using dynamic light scattering and cryogenic-transmission electron microscopy (cryo-TEM). A Franz diffusion cell is employed to determine the delivery efficiency of various liposomes, where all liposomes do not exhibit any recognizable difference of permeation through the synthetic membrane. When the fluorescence liposomes are applied to 3D skin, considerable fluorescence intensity is observed at the stratum cornea and epithelium layers. Compared to other liposomes, cationic liposomes exhibit the highest fluorescence intensity, suggesting the enhanced permeation of liposomes through the 3D skin layers. Finally, the ability of niacinamide (NA)-incorporated liposomes to suppress melanin transfer in pigmented 3D skin is examined, where cationic liposomes exhibit the highest degree of whitening effects.

Details of thermal behavior of spin-coated film of biodegradable poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer studied by principal component analysis-based two-dimensional (PCA2D) correlation spectroscopy.

Principal component analysis-based two-dimensional (PCA2D) correlation spectroscopy was applied to the temperature-dependent infrared-reflection absorption (IRRAS) spectra of a spin-coated film of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P(HB-co-HHx)) (HHx=7.2 mol%) copolymer. In asynchronous PCA2D correlation spectra, we clearly captured the existence of two components in the crystalline band of the CO stretching mode, well-ordered primary crystals observed at lower wavenumber and less ordered secondary crystals observed at higher wavenumber, which is not readily detectable in the original 1D spectra. Furthermore, the intensity changes of bands at 1298 and 1280 cm(-1) are significantly different in the temperature ranges below and above the transition temperature around 140 degrees C identified by the 2D first derivatives plot. The result further confirms that the sequence of intensity changes with increasing temperature is such that bands for less ordered crystalline components of P(HB-co-HHx) (HHx=7.2 mol%) are changing first at an earlier (i.e., lower temperature) stage.

Two-dimensional gradient mapping technique useful for detailed spectral analysis of polymer transition temperatures.

This paper demonstrates the potential of a two-dimensional (2D) gradient mapping technique that utilized the eigenvalue manipulating transformation (EMT) of the spectral data set. The EMT technique, by lowering the power of a set of eigenvalues associated with the original data, enhances the contributions of minor principle components (PCs). The operation converts the original spectral data set to the one with subtle differences among the responses of the system being exaggerated. Small shoulders and obscure minor features may become much more visible, because such small differentiating features are often captured only by the minor PCs enlarged by the EMT treatment. This improvement for 2D mapping is potentially very important to determine the transition temperatures, which are not readily detected in convention spectral analysis.

New approach to generalized two-dimensional correlation spectroscopy. II: Eigenvalue manipulation transformation (EMT) for noise suppression.

This paper introduces the concept of eigenvalue manipulating transformation (EMT) of a data matrix for noise suppression in two-dimensional (2D) correlation spectroscopy. The FT-IR spectra of a polystyrene/methyl ethyl ketone/toluene solution mixture during the solvent evaporation process, to which were added a substantial amount of artificial noise, have been analyzed. By uniformly raising the power of a set of eigenvalues, the major eigenvalues become more prominent. As a consequence, minor eigenvectors representing the noise component are no longer strongly represented in the reconstructed data. This EMT operation is similar to the simple truncation of noise-dominated minor factors practiced in standard principal component analysis (PCA), as demonstrated in our preceding paper on PCA-2D correlation spectroscopy. The effect of this new EMT scheme is more gradual, with attractive flexibility to continuously fine-tune the balance between the desired noise reduction effect and the retention of pertinent spectral information.

New approach to generalized two-dimensional correlation spectroscopy. III: Eigenvalue manipulation transformation (EMT) for spectral selectivity enhancement.

This paper demonstrates the potential of eigenvalue manipulating transformation (EMT) of a data matrix for spectral selectivity enhancement, especially useful in 2D correlation analysis. The EMT operation aims at the accentuation of select features of the information content of the original data matrix. For example, by uniformly lowering the power of a set of eigenvalues associated with the original data, the smaller eigenvalues become more prominent and the contributions of secondary loadings become amplified. As a direct consequence of the minor factor accentuation by such EMT operations, 2D correlation spectra gain much stronger discriminating power. The selectivity enhancement effect of such manipulation of eigenvalues is much more noticeable on the synchronous 2D correlation spectrum. This improvement for the spectral selectivity of synchronous 2D correlation spectra is potentially very important, as we usually put more emphasis on the interpretation of asynchronous 2D spectra in 2D correlation analysis due to overlaps of synchronous peaks. Such EMT operations tend to exaggerate the information content of minor PCs and reduce that of major PCs. Thus, much more subtle difference of spectral behavior for each component is now highlighted. Surprisingly, asynchronous 2D correlation spectra are found to be much less sensitive to such EMT operations. The result indicates that the distinction of different band responses has already been accomplished effectively by the original asynchronous 2D correlation analysis.

Two-dimensional heterospectral correlation analysis of X-ray photoelectron spectra and infrared spectra for spin-coated films of biodegradable poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymers.

We investigated the thermal behavior of spin-coated films of biodegradable poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P(HB-co-HHx)) copolymers at the molecular level. To better understand details of thermal behavior of spin-coated films of P(HB-co-HHx) copolymers, we applied two-dimensional (2D) correlation analysis to the spectra of P(HB-co-HHx) (HHx = 12.0, 10.0, and 3.8 mol %) copolymers during the heating process from 30 to 150 degrees C as obtained by temperature-dependent infrared-reflection absorption spectroscopy and X-ray photoelectron spectroscopy (XPS). 2D IR and 2D XPS correlation spectra of spin-coated films of P(HB-co-HHx) copolymers clearly revealed the sequence of intensity changes with increasing temperature: an amorphous band increases first and then a band for less ordered secondary crystals decreases before a band for well-ordered primary crystals. Furthermore, the synchronous 2D heterospectral XPS/IR correlation spectrum elucidated the correlation between the IR and XPS bands, confirming their band assignments. The asynchronous 2D heterospectral correlation spectrum revealed the probe-dependent asynchronicity between XPS and IR signals arising from the same species even under identical perturbation conditions because of the different scales of molecular changes probed. It clearly provides a complete interpretation of the phase transition phenomenon of P(HB-co-HHx) copolymers, which could not have been obtained through XPS or IR study alone, and also, the results obtained thereof offer a new insight into the molecular interactions as well observed by two different probes.