E - equipment calibration

Chernoff, L

doi:10.6028/nbs.rpt.9433

Cited by 2 publications

(2 citation statements)

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“…[13][14][15][16][17][18][19][20][21][22][23][24] Studies on individual collagen fibrils form the basis for an in-depth understanding of AFM data on structurally more complex collagenous tissues. 14,16,20,[25][26][27][28] AFM-based methods have been used for imaging dry collagen fibrils 13,29,30 and for measuring their local elastic modulus and viscoelastic properties. 15,18,22,24,[31][32][33] With nanoindentation and AFM-based tip indentation, the fibril's mechanical response perpendicular to the fibril's axis is measured, whereas with microtensile testing experiments, the mechanical response along the fibril's axis is probed.…”

Section: Introductionmentioning

confidence: 99%

Unraveling capillary interaction and viscoelastic response in atomic force microscopy of hydrated collagen fibrils

Uhlig

Magerle

2017

Nanoscale

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The mechanical properties of collagen fibrils depend on the amount and the distribution of water molecules within the fibrils. Here, we use atomic force microscopy (AFM) to study the effect of hydration on the viscoelastic properties of reconstituted type I collagen fibrils in air with controlled relative humidity. With the same AFM tip, we investigate the same area of a collagen fibril with two different force spectroscopy methods: force-distance (FD) and amplitude-phase-distance (APD) measurements. This allows us to separate the contributions of the fibril's viscoelastic response and the capillary force to the tip-sample interaction. A water bridge forms between the tip apex and the surface, causing an attractive capillary force, which is the main contribution to the energy dissipated from the tip to the specimen in dynamic AFM. The force hysteresis in the FD measurements and the tip indentation of only 2 nm in the APD measurements show that the hydrated collagen fibril is a viscoelastic solid. The mechanical properties of the gap regions and the overlap regions in the fibril's D-band pattern differ only in the top 2 nm but not in the fibril's bulk. We attribute this to the reduced number of intermolecular crosslinks in the reconstituted collagen fibril. The presented methodology allows the mechanical surface properties of hydrated collagenous tissues and biomaterials to be studied with unprecedented detail on the nanometer scale.

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Section: Introductionmentioning

confidence: 99%

Unraveling capillary interaction and viscoelastic response in atomic force microscopy of hydrated collagen fibrils

Uhlig

Magerle

2017

Nanoscale

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“…1 It is composed of three polypeptide a chains coiled around a central axis to form a triple helical structure, 2 which is $300 nm in length and $1.5 nm in diameter, stabilised by intermolecular hydrogen and bound water molecules. 4,5 To date, there are about 28 genetically distinct collagen types identied, based on the differences in their polypeptide sequence. Each bril contains thousands of collagen molecules which in turn, is stabilised by the presence of intermolecular crosslinks.…”

Section: Introductionmentioning

confidence: 99%

Multimodal optical characterisation of collagen photodegradation by femtosecond infrared laser ablation

Manickavasagam

Hirvonen

Melita

et al. 2014

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Collagen is a structural component of the human body, as a connective tissue it can become altered as a result of pathophysiological conditions. Although the collagen degradation mechanism is not fully understood, it plays an important role in ageing, disease progression and applications in therapeutic laser treatments. To fully understand the mechanism of collagen alteration, in our study photo-disruptive effects were induced in collagen I matrix by point-irradiation with a femtosecond Ti-sapphire laser under controlled laser ablation settings. This was followed by multi-modal imaging of the irradiated and surrounding areas to analyse the degradation mechanism. Our multi-modal methodology was based on second harmonic generation (SHG), scanning electron microscope (SEM), autofluorescence (AF) average intensities and the average fluorescence lifetime. This allowed us to quantitatively characterise the degraded area into four distinct zones: (1) depolymerised zone in the laser focal spot as indicated by the loss of SHG signal, (2) enhanced crosslinking zone in the inner boundary of the laser induced cavity as represented by the high fluorescence ring, (3) reduced crosslinking zone formed the outer boundary of the cavity as marked by the increased SHG signal and (4) native collagen. These identified distinct zones were in good agreement with the expected photochemical changes shown using Raman spectroscopy. In addition, imaging using polarisation-resolved SHG (p-SHG) revealed both a high degree of fibre re-orientation and a SHG change in tensor ratios around the irradiation spot. Our multi-modal optical imaging approach can provide a new methodology for defining distinct zones that can be used in a clinical setting to determine suitable thresholds for applying safe laser treatments without affecting the surrounding tissues. Furthermore this technique can be extended to address challenges observed in collagen based tissue engineering and used as a minimally invasive diagnostic tool to characterise diseased and non-diseased collagen rich tissues.

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E - equipment calibration

Cited by 2 publications

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Unraveling capillary interaction and viscoelastic response in atomic force microscopy of hydrated collagen fibrils

Unraveling capillary interaction and viscoelastic response in atomic force microscopy of hydrated collagen fibrils

Multimodal optical characterisation of collagen photodegradation by femtosecond infrared laser ablation

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