Protein-based coatings are of immense interest due to their rich biological functions. Layer-by-layer (LbL) assembly, as a powerful means of transferring protein functions to the material surface, has received widespread attention. However, the assembly mechanism of protein-based LbL coatings is still far from being explained, not only because of protein structure and function diversity but also characterization limitations. Herein, we monitored in situ the LbL assembly process of tannic acid (TA) and lysozyme (Lyz), a classic pair of polyphenol and protein, by combining quartz crystal microbalance with dissipation monitoring (QCM-D) and spectroscopic ellipsometry (SE). The water content, morphology, mechanical properties, antioxidant activity, and the driving force of TA-Lyz coating engineered under different pH values were analyzed in detail by various techniques. The water content, a key factor in TA-Lyz coatings, increased with increasing assembled pH values, which resulted in a porous morphology, inhomogeneous mechanical distribution, faster assembly growth, and better antioxidant activity in both acellular and cellular levels. In addition, high water content is unfavorable to both entropy and enthalpy changes, and the thermodynamic driving force of TA and Lyz assembly mainly comes from the enthalpy change brought by the noncovalent interaction between TA and Lyz. These results provide new insights into engineering the structure, function, and assembly mechanisms of protein-based coatings.
BACKGROUND AND PURPOSE: No MR imaging measurement criteria are available for the diagnosis of optic nerve atrophy. We determined a threshold optic nerve area on MR imaging that predicts a clinical diagnosis of optic nerve atrophy and assessed the relationship between optic nerve area and retinal nerve fiber layer thickness measured by optical coherence tomography, an ancillary test used to evaluate optic nerve disorders. MATERIALS AND METHODS: We evaluated 26 patients with suspected optic nerve atrophy (8 with unilateral, 13 with bilateral and 5 with suspected but not demonstrable optic nerve atrophy) who had both orbital MR imaging and optical coherence tomography examinations. Forty-five patients without optic nerve atrophy served as controls. Coronal inversion recovery images were used to measure optic nerve area on MR imaging. Retinal nerve fiber layer thickness was determined by optical coherence tomography. Individual eyes were treated separately; however, bootstrapping was used to account for clustering when appropriate. Correlation coefficients were used to evaluate relationships; receiver operating characteristic curves, to investigate predictive accuracy. RESULTS: There was a significant difference in optic nerve area between patients' affected eyes with optic nerve atrophy (mean, 3.09 Ϯ 1.09 mm 2), patients' unaffected eyes (mean, 5.27 Ϯ 1.39 mm 2 ; P ϭ .008), and control eyes (mean, 6.27 Ϯ 2.64 mm 2 ; P Ͻ .001). Optic nerve area Յ 4.0 mm 2 had a sensitivity of 0.85 and a specificity of 0.83 in predicting the diagnosis of optic nerve atrophy. A significant relationship was found between optic nerve area and retinal nerve fiber layer thickness (r ϭ 0.68, P Ͻ .001). CONCLUSIONS: MR imaging-measured optic nerve area Յ 4.0 mm 2 has moderately high sensitivity and specificity for predicting optic nerve atrophy, making it a potential diagnostic tool for radiologists. ABBREVIATIONS: OCT ϭ optical coherence tomography; ONA ϭ optic nerve atrophy; ON area ϭ optic nerve area; RNFL ϭ retinal nerve fiber layer; ROC ϭ receiver operating characteristic
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