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Chitin derivatives coatings on titanium surfaces

Maria Stefania Massaro

Chitin derivatives coatings on titanium surfaces.

Rel. Silvia Spriano, Sara Ferraris. Politecnico di Torino, Corso di laurea magistrale in Ingegneria Biomedica, 2019

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Abstract:

When a biomaterial is implanted in the body as part of a therapeutic or diagnostic procedure, requires the stimulation of a proper response from the body. In order to modulate the host response and reduce inflammation, the interface between the biomaterial and the body can be functionalised with polymers, proteins or molecules with antibacterial and anti-inflammatory behaviour. Chitin derivatives, extracted from crustacean shells, can be used to modulate the host response to an implant with a nanotextured coating. Since chitin is a waste product of the food industry, its use as a coating has a green approach to recycle and transform a waste into a high added value product. Titanium alloy samples are coated with chitin derivatives using different procedures to verify their efficacy both in terms of resistance of the attachment and of difficulty of the procedure. Chitin derivatives are attached to oxidised titanium through physical attachment, through a good leaving group (tresyl chloride) and through a coupling agent (polydopamine). Titanium was oxidised first to improve the adhesion possibilities and chitin derivatives were dissolved or suspended in different solutions. Physical attachment implies a direct bonding between the polymer and the substrate, while the leaving group provides an active site for the adhesion and the coupling agent act as interface to which both chitin derivatives and the substrate adhere. In the physical attachment coating chitin derivatives were dissolved in acetic acid or suspended in a PBS (phosphate buffered saline) solution. In PBS chitin derivatives generate a suspension because pH is 7.4 and chitin derivatives dissolve when pH is below 6.5. The use of a leaving group requires the activation of the substrate by immersion in tresyl chloride and chitin derivatives are suspended in a PBS solution. The procedure is carried out at room temperature or at 37°C. Polydopamine is a coupling agent that reacts with amine functional groups present in chitin derivatives. After the adhesion of polydopamine, chitin derivatives were attached through dissolution in deionized water, suspension in PBS or dissolution in a buffer containing MES, NHS and EDC. Samples are analysed with spectroscopy, microscopy, zeta potentials, contact angle and tape test. FTIR spectra allowed a qualitative assessment of the coatings through the intensities of characteristic functional groups showed by chitin derivatives (OH stretching and C=O vibration of carboxylic acid). AFM images showed that physical attachment of chitin derivatives resulted in a reduction in the overall roughness compared to oxidised titanium that is required to improve the anti-inflammatory behaviour since macrophages prefer more roughened surfaces. SEM images allowed to analyse the percentage of area coated in the samples and the type of adhesion. Zeta potential is a measure of the superficial charge on a sample via streaming potential. This analysis can be used to verify the uniformity of the coating by comparing its value for the sample with previous literature, assuming that a uniform coating shows values similar to chitin derivatives. Contact angles provide the wettability of a substrate while tape test is a measure of the resistance of the coating to taping. A classification of the sample after taping indicates a strong adhesion when the results obtained shows the presence of the coating. The analysis of all samples allowed to assess the efficacy of chitin d

Relators: Silvia Spriano, Sara Ferraris
Academic year: 2018/19
Publication type: Electronic
Number of Pages: 87
Subjects:
Corso di laurea: Corso di laurea magistrale in Ingegneria Biomedica
Classe di laurea: New organization > Master science > LM-21 - BIOMEDICAL ENGINEERING
Aziende collaboratrici: Innovation Center Iceland
URI: http://webthesis.biblio.polito.it/id/eprint/10700
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