Incoherent Second Harmonic Generation (SHG) from goldnanoparticles,also known as hyper-Rayleigh scattering (HRS), is proposed as a sensingmethod for copper(II) ions. As opposed to colorimetry-based methodsrelying on the shift of the localized surface plasmon resonance withthe copper(II) concentration, which effectively scales with the nanoparticlevolume due to the origin of the absorption phenomenon, SHG relieson the surface origin of the response for sufficiently small nanoparticles.As a result, differences can be expected that could be potentiallyturned into advantages such as improved Limit of Detection and shorterdetection response time. The present study demonstrates that the SHGlight scattered from aqueous suspensions of gold nanoparticles inthe presence of copper(II) ions is indeed sensitive to the copper(II)ion concentration changes. A first approach based on intensity changesshows that there is a competition between the formation of corona-likestructures centered around the gold nanoparticles due to the ionicinteraction between copper(II) ions and the negatively charged citrate-coatednanoparticles on one side and, on the other side, aggregation of nanoparticlesdue to charge screening as the copper(II) bromide concentration increases.The former process dominates at low copper(II) concentrations, whereasaggregation takes over above 1 mM copper(II) concentrations. A figureof merit is thus designed in order to provide a quantitative assessmentof the sensing performance. In a further analysis, a polarizationresolved study of the SHG light scattered from the gold nanoparticlesallows the determination of other figures of merit. The first onebased on the depolarization ratio seems appropriate, as it is basedon the surface origin of the SHG response from gold nanoparticles,whereas the second one, based on the retardation parameter, shouldnot perform better than those derived from colorimetry methods.

Disentangling Second Harmonic Generation (SHG) and Multiphoton Excited Photoluminescence (MEPL) signals in microscopy experiments is not an easy task. Two methods have been so far proposed based either on a time domain or a spectral domain analysis of the collected signals. In this report, a new method based on polarization discrimination is proposed to separate these SHG and MEPL contributions. In order to demonstrate this operation, intensity depth profiles are recorded for an anatase titanium dioxide powder consisting of 22 nm diameter nanoparticles using ultrafast femtosecond laser excitation. Polarization analysis of these intensity depth profiles is therefore performed and demonstrate a polarization angle shift for the SHG intensity contribution as compared to the MEPL one, allowing for the discrimination of the two SHG and MEPL contributions. The fundamental beam is set at two different wavelengths in order to provide a SHG photon energy above and below the anatase TiO 2 band-gap of 3.2 eV, leading to a change in the relative intensity weight and a spectral shift between the SHG and MEPL contributions. This operation further demonstrates the potential of the method when the spectral domain disentangling cannot be performed. SHG profiles are by far narrower than those of MEPL. This study where both SHG and MEPL contributions are observed offers perspectives in photonics of powder materials as the different origin and properties of the two processes can be separated.

Introduction: The functionalization of titanium (Ti) and titanium alloys (Ti6Al4V) implant surfaces via material-specific peptides influence host/biomaterial interaction. The impact of using peptides as molecular linkers between cells and implant material to improve keratinocyte adhesion is reported.Results: The metal binding peptides (MBP-1, MBP-2) SVSVGMKPSPRP and WDPPTLKRPVSP were selected via phage display and combined with laminin-5 or E-cadherin epithelial cell specific peptides (CSP-1, CSP-2) to engineer four metal-cell specific peptides (MCSPs). Single-cell force spectroscopy and cell adhesion experiments were performed to select the most promising candidate. In vivo tests using the dental implant for rats showed that the selected bi functional peptide not only enabled stable cell adhesion on the trans-gingival part of the dental implant but also arrested the unwanted apical migration of epithelial cells.Conclusion: The results demonstrated the outstanding performance of the bioengineered peptide in improving epithelial adhesion to Ti based implants and pointed towards promising new opportunities for applications in clinical practice.

Sarcomere length (SL) and its variation along the myofibril strongly regulate integrated coordinated myocyte contraction. It is therefore important to obtain individual SL properties. Optical imaging by confocal fluorescence (for example, using ANEPPS) or transmitted light microscopy is often used for this purpose. However, this allows for the visualization of structures related to Z-disks only. In contrast, second-harmonic generation (SHG) microscopy visualizes A-band sarcomeric structures directly. Here, we compared averaged SL and its variability in isolated relaxed rat cardiomyocytes by imaging with ANEPPS and SHG. We found that SL variability, evaluated by several absolute and relative measures, is two times smaller using SHG vs. ANEPPS, while both optical methods give the same average (median) SL. We conclude that optical methods with similar optical spatial resolution provide valid estimations of average SL, but the use of SHG microscopy for visualization of sarcomeric A-bands may be the “gold standard” for evaluation of SL variability due to the absence of optical interference between the sarcomere center and non-sarcomeric structures. This contrasts with sarcomere edges where t-tubules may not consistently colocalize to Z-disks. The use of SHG microscopy instead of fluorescent imaging can be a prospective tool to map sarcomere variability both in vitro and in vivo conditions and to reveal its role in the functional behavior of living myocardium.