Delivery of antimicrobial biomaterials through additive manufacturing

Lowther, Morgan ORCID: 0000-0001-6722-5173 (2022). Delivery of antimicrobial biomaterials through additive manufacturing. University of Birmingham. Ph.D.

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Abstract

Reconstruction of hard tissues is increasingly challenged by post-operative bone and implant related infections. For low risk elective orthopaedic procedures such as joint replacements, 22 % of revision surgeries are motivated by infection. This clinical need is compounded with a growing incidence of bacterial resistance to antimicrobials, particularly antibiotics.

To tackle this, a biomaterials driven approach to reducing reliance on conventional antibiotics for infection management is needed. Inherently antimicrobial materials that do not rely upon conventional antibiotic chemistries offer a promising supplement to typical post operative prophylaxes. This thesis focusses on the formulation of antimicrobial materials, with a view to their delivery in additively manufactured implants.
First, an antimicrobial cement formulation is investigated. An injectable magnesium oxychloride cement (MOC) was formulated, and the effect of doping with silver phosphate as an antimicrobial agent considered. Whilst silver doped MOC showed sustained Ag release over 14 days and enhanced efficacy in vitro, undoped MOC also showed significant inherent antimicrobial behaviour. Preliminary studies of two-phase additively manufactured implants were made.

Second, novel Ti-Ag alloy microstructures were produced through laser powder bed fusion (L-PBF) additive manufacturing. Blended elemental feedstocks were manufactured with a range of laser parameters, with resulting microstructures ranging from highly segregated to homogenised. Statistical analysis demonstrated in-situ spread induced demixing of the powder blend, with varying Ag content across the build bed.
Finally, the possible mode of action of antimicrobial Ti-Ag alloys was assessed. Despite previous assertions that specific intermetallic phases dominate efficacy, high Ti2Ag content alloys showed no statistically significant change in antimicrobial action versus control samples. This study further indicates the poorly understood nature of antimicrobial alloys, and the need for more in depth mechanistic investigations.

Together, this work contributes to the growing need for biomaterials driven approaches to infection prevention in hard tissue reconstruction.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):