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Semiconducting single-walled carbon nanotubes (SWCNTs) are among the few photostable optical emitters that are ideal for sensing, imaging, drug delivery, and monitoring of protein activity. These applications often require strategies for immobilizing proteins onto the nanotube while preserving the optical properties of the SWCNTs. Site-specific and oriented immobilization strategies, in particular, offer advantages for improving sensor and optical signaling responses. In this study, we demonstrate site-specific protein immobilization of a model of enhanced yellow fluorescent protein with a single engineered cysteine residue, using either single-stranded DNA or a pyrene-containing linker to interact with the SWCNT surface. Protein expression and bioconjugation were characterized using a combination of gel electrophoresis, absorbance, fluorescence, mass spectrometry, and circular dichroism measurements. The results confirm successful protein immobilization onto SWCNTs, which retain their near-infrared fluorescence following conjugation. The successful demonstration of these bioconjugation strategies serves as a basis for more cost-effective, site-specific immobilization strategies that can help preserve protein folding and functionality.

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The most common reasons for hard-tissue implant failure are structural loosening and prosthetic infections. Hence, to fix the first problem, different bioinspired coatings were applied to the titanium alloy surfaces in this study, including dual acid-etched, anodic TiO2 nanotubes array (TNTs), anodic hierarchical titanium oxide, micro- and nanostructured hydroxyapatite (HA) layers, and HA/chitosan (HA/CS) nanocomposite coating. XRD and FTIR analysis demonstrated that the in situ HA/chitosan nanocomposite formed successfully. The MTT assay showed that all samples had excellent cell viability, with cell proliferation rates ranging from 120-150% after 10 days. The hierarchical coating demonstrated superhydrophilicity (θ ≈ 0°) and increased the wettability of the metallic Ti surface by more than 120%. The friction coefficient of all fabricated surfaces was within the range of natural bone's mechanical behavior. The intermediate hierarchical oxide layer increased the adhesion strength of the HA/chitosan coating by more than 60%. The Hierarchical middle oxide layer caused the mechanical stability of HA/CS during the 1000 m of friction test. The microhardness of HA/CS (22.5 HV) and micro-HA (25.5 HV) coatings was comparable to that of human bone. An intermediate hierarchical oxide-based mechanism for improving adhesion strength in HA/CS coatings was presented.

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