Responsive poly (γ-glutamic acid) fibres for biomedical applications.

A novel responsive system using a protein-based biopolymer was designed to undergo structural, geometric, and chemical changes upon temperature change or solvent interaction. Poly(γ-glutamic acid) (γ-PGA) is an attractive candidate for various biomedical applications as it is naturally produced, biocompatible and enzymatically degradable. The responsive material was fabricated using an electrospun modified γ-PGA to create a sub-micron fibrous mat. By modulating the environment responsive behaviour in a controlled manner, exciting applications such as wound dressing, compression materials and self-tightening knots are envisaged.

Two-photon luminescence microscopy oflarge-area gold nanostructures on templates of anodized aluminum.

Using linear reflection spectroscopy and far-field two-photon luminescence (TPL) scanning optical microscopy, we characterize highly enhancing, large-area gold nanostructures formed on porous templates made by anodization of aluminum with either oxalic acid or phosphoric acid. These templates are formed by a newly developed, stepwise technique making use of protective top oxide layers facilitating continuously tunable interpore distances. The upper, porous alumina layers are subsequently removed and the remaining embossed barrier layer is used as template for the sputtered gold, where the density of gold particles covering the sample is adjusted by regulating the sputtering conditions. We observe spatially averaged field intensity enhancement (FE) factors of up to ~5.210(2) and bright spots in the TPL-images exhibiting maximum FE factors of up to approximately 1410(2) which is the largest estimated FE from any hitherto examined structures with our setup. We relate this large-area massive FE to constructive interference of surface plasmon (SP) polaritons scattered from the densely packed, randomly distributed gold particles and directly correlate this particle density with the strong and broad SP resonances as well as the magnitude of the FE factors. The average FE and the position of high enhancements in the TPL-images are dictated by the excitation wavelength, and the structures could evidently serve as versatile structures facilitating practical molecular sensing.

Discriminating isogenic cancer cells and identifying altered unsaturated fatty acid content as associated with metastasis status, using k-means clustering and partial least squares-discriminant analysis of Raman maps.

Raman spectroscopy is a label-free, real-time diagnostic tool that shows great promise in identifying cell differences. We have evaluated the discriminatory power of Raman spectroscopy using a unique model system consisting of two isogenic cancer cell lines derived from the MDA-MB-435 cell line. The two cell lines are equally tumorigenic in mice, but while M-4A4 gives rise to metastasis, NM-2C5 only disseminates single cells that remain dormant in distant organs. Previous comparative proteomic and transcriptomic analyses of the two cell lines have shown that they differ only in the expression level of a few proteins and genes. Raman maps were recorded of single cells after fixation and drying using 785 nm laser excitation. K-means clustering reduced the amount of data from each cell and improved the signal-to-noise ratio of cluster-averaged spectra. Spectra representing the nucleus were discarded as they showed much smaller differences between the two cell lines compared to cytoplasm spectra. Partial least squares-discriminant analysis (PLS-DA) was applied to distinguish the two cell lines. A cross-validated PLS-DA resulted in 92% correctly classified samples. Spectral differences were assigned to a higher unsaturated fatty acid content in the metastatic vs nonmetastatic cell line. Our study demonstrates the unique ability of Raman spectroscopy to distinguish minute differences at the subcellular level and yield new biological information. Our study is the first to demonstrate the association between polyunsaturated fatty acid content and metastatic ability in this unique cell model system and is in agreement with previous studies on this topic.