Use of silver-based additives for the development of antibacterial functionality in Laser Sintered polyamide 12 parts

Abstract

Infectious diseases (exacerbated by antimicrobial resistance) cause death, loss of quality of life and economic burden globally. Materials with inherent antimicrobial properties offer the potential to reduce the spread of infection through transfer via surfaces or solutions, or to directly reduce microbial numbers in a host if used as implants. Additive Manufacturing (AM) techniques offer shorter supply chains, faster delivery, mass customisation and reduced unit costs, as well as highly complicated part geometries which are potentially harder to clean and sterilise. Here, we present a new approach to introducing antibacterial properties into AM, using Laser Sintering, by combining antimicrobial and base polymer powders prior to processing. We demonstrate that the mechanical properties of the resultant composite parts are similar to standard polymer parts and reveal the mode of the antibacterial activity. We show that antibacterial activity is modulated by the presence of obstructing compounds in different experimental media, which will inform appropriate use cases. We show that the material is not toxic to mammalian cells. This material could be quickly used for commercial products, and our approach could be adopted more generally to add new functionality to Laser Sintered parts. The global Additive Manufacturing (AM) market has grown by an average of 26.9% annually for the last 30 years, with the overall revenue of the industry currently estimated at $9.8 billion, and aerospace, automotive and healthcare being major sectors 1. Parts are produced in a layer-by-layer manner, directly from a Computer-Aided Design (CAD) file. This layer-by-layer approach provides key benefits through removing the need for tooling and increasing the ease with which complex geometries can be produced. However, despite their clear potential, the range of materials that can be used in AM processes is limited compared to more traditional manufacturing techniques, which in turn has restricted the range of applications in which they can be used. Laser Sintering is an AM technology that produces parts by selectively scanning and melting consecutive cross-sections of polymer powder particles. Areas which have not been scanned remain as loose powder throughout the process, acting to support any overhanging areas, which in turn allows the economic production of highly complex part geometries. This geometric capability makes Laser Sintering highly suited to production of complex, optimised, products and devices, or to the production of products and devices personalised to individuals. However, particularly when considering hand-held and/or medical products, increasing geometric complexity can render them difficult and time-consuming to clean effectively, potentially providing increased chance of spread of bacteria. Incorporation of antibacterial properties into the parts themselves could reduce or eliminate this risk, and is the focus of this work. Many antimicrobial products are currently available to purchase, with a growing global market fo...

Antimicrobial 3D Printed Objects in the Fight Against Pandemics

“…13 The areas of loose powder that are not scanned during a print act as supports for any overhanging areas of the print allowing complex geometries to be created with less waste of materials in the generation of supports. 14 Both SLA and SLS, require post print processing steps that creates the need for additional materials and equipment, which can be a disadvantage during a pandemic environment as products needed to be created rapidly, within a short period of time. Moreover, potential toxicity issues in SLA printed parts need also to be considered, as can be caused by leaching of photoinitiator residues, which are prominently cytotoxic, and in some other cases due to incomplete printing or post-curing items.…”

3D Printing Technology for Fighting COVID-19 Pandemic

“…This tactic can be further explored in other implants to elute antibiotics post-implantation. Apart from post-processing step to equip the final product with antibacterial and microbial agents, the product itself can be made of metals (such as silver, copper, and zinc) which possess biocidal properties (Turner et al 2020). Scientists have also explored in situ functionalization while manufacturing, by adding fillers to the main material.…”

3D Printing of Metal/Metal Oxide Incorporated Thermoplastic Nanocomposites With Antimicrobial Properties

“…This process is repeated until the intended model is completed (Paul and Anand, 2012;Valino et al, 2019). For this approach, addition of powder M/MO nanoparticles with the polymer powder is done by mechanical mixers such as rotary tumblers (Turner et al, 2020). The mixing process is easier and can result in a more uniform distribution of nanoparticles when compared to FDM.…”

“…They also tested these nanocomposites with real patients and demonstrated that this manufacturing approach is a promising treatment option for patients diagnosed with complete edentulism (Totu et al, 2017;Cristache et al, 2020). Turner et al (2020) introduced a SLS printing of antibacterial nanocomposite by mixing polyamide 12 with 1% of commercially available B65003 silver additives to make delicate, complex, and personalized devices for medical and healthcare applications (Turner et al, 2020).…”