Using the FT-IR linear dichroism method for molecular order determination of tendon collagen bundles and nylon 6

Polarized Fourier transform-infrared (FT-IR) was used to compare the orientation of vibrational chemical groups of bovine tendon collagen bundles (CBs) to that of nylon 6, a simpler polyamide model, in terms of linear dichroism (LD). Subtraction of spectral profiles identified the most significant differences regarding the amide regions. At 1630cm(-1), the CBs displayed higher peak areas and absorbance when positioned perpendicularly (A⊥) to the plane of polarized light, in comparison with nylon 6. In contrast, at the 1526cm(-1) amide II spectral region the inverse occurred. In the amide III region (1232cm(-1)), the LD was positive and higher for CBs. Dichroic ratios (DR=A||/A⊥) calculated from the average of ten measured spectra for CBs and nylon 6 revealed that the values for CBs were <1.0 in the 3298-1655cm(-1) wavenumber range and >1.0 in the 1536-1234cm(-1) wavenumber range. From 1535 to 1120cm(-1), nylon 6 displayed DR values higher than those of CBs. The LD band integrated areas were higher in CBs than in nylon 6. The LD differences between CBs and nylon 6 are probably due to a more complex chemical composition and supramolecular oriented architecture in CBs in comparison to nylon 6.

Fluorescence, aggregation properties and FT-IR microspectroscopy of elastin and collagen fibers

Histological and histochemical observations support the hypothesis that collagen fibers can link to elastic fibers. However, the resulting organization of elastin and collagen type complexes and differences between these materials in terms of macromolecular orientation and frequencies of their chemical vibrational groups have not yet been solved. This study aimed to investigate the macromolecular organization of pure elastin, collagen type I and elastin-collagen complexes using polarized light DIC-microscopy. Additionally, differences and similarities between pure elastin and collagen bundles (CB) were investigated by Fourier transform-infrared (FT-IR) microspectroscopy. Although elastin exhibited a faint birefringence, the elastin-collagen complex aggregates formed in solution exhibited a deep birefringence and formation of an ordered-supramolecular complex typical of collagen chiral structure. The FT-IR study revealed elastin and CB peptide NH groups involved in different types of H-bonding. More energy is absorbed in the vibrational transitions corresponding to CH, CH2 and CH3 groups (probably associated with the hydrophobicity demonstrated by 8-anilino-1-naphtalene sulfonic acid sodium salt [ANS] fluorescence), and to νCN, δNH and ωCH2 groups of elastin compared to CB. It is assumed that the α-helix contribution to the pure elastin amide I profile is 46.8%, whereas that of the B-sheet is 20% and that unordered structures contribute to the remaining percentage. An FT-IR profile library reveals that the elastin signature within the 1360-1189cm(-1) spectral range resembles that of Conex-Toray aramid fibers.

Biomimetic hydrogels with mesoscale collagen architecture for patient-derived tumor organoids culture

Patient-derived tumor organoids (PDTOs) shows great potential as a preclinical model. However, the current methods for establishing PDTOs primarily focus on modulating local properties, such as sub-micrometer topographies. Nevertheless, they neglect to capture the global millimeter or intermediate mesoscale architecture that have been demonstrated to influence tumor response to therapeutic treatment and tumor progression. In this study, we present a rapid technique for generating collagen bundles with an average length of 90 ± 27 μm and a mean diameter of 5 ± 1.5 μm from tumor tissue debris that underwent mechanical agitation following enzymatic digestion. The collagen bundles were subsequently utilized for the fabrication of biomimetic hydrogels, incorporating microbial transglutaminase (mTG) crosslinked gelatin. These biomimetic hydrogels, referred to as MC-gel, were specifically designed for patient-derived tumor organoids. The lung cancer organoids cultured in MC-gel exhibited larger diameters and higher cell viability compared to those cultured in gels lacking the mesoscale collagen bundle; moreover, their irregular morphology more closely resembled that observed in vivo. The MC-gel-based lung cancer organoids effectively replicated the histology and mutational landscapes observed in the original donor patient's tumor tissue. Additionally, these lung cancer organoids showed a remarkable similarity in their gene expression and drug response across different matrices. This recently developed model holds great potential for investigating the occurrence, progression, metastasis, and management of tumors, thereby offering opportunities for personalized medicine and customized treatment options.