# 3D Printed Antibacterial Prostheses
## 4 Discussion
Furthermore, the fabrication of antibacterial sockets of definitive upper limb prostheses may have the potential to alleviate the majority of skin disorders associated with bacterial and fungal infections [10; 12]. The development of an antibacterial 3D printing filament with thermoforming capabilities has the potential to revolutionize patient care in the orthotic and prosthetic industry. The addition of copper nanoparticles to polymers, and the resulting antimicrobial properties have promising applications in the development of medical devices associated with bacterial development [12]. These applications are not limited to post-operative prostheses [12; 18], but can also be used as other types of medical devices, such as wound dressings [13] and surgical instruments [28]. Wound dressings are external barriers that isolate the injury site from the external environment and provide an optimal environment for the wound to heal. When a wound occurs due to trauma or disease, the barrier becomes compromised. This can increase the susceptibility of the wound site to microbial infections originating from endogenous and exogenous sources. A previous investigation [13] used zinc, copper, and silver particles incorporated into polycaprolactone to develop patient-specific 3D printed antimicrobial wound dressings. The authors found that wound dressings manufactured using 3D printing filament containing particles of silver and copper had the most potent bactericidal properties. Specifically, these wound dressings showed the most bactericidal properties against methicillin-resistant _Staphylococcus aureus_ which is a common cause of bacterial skin infections. Similarly, the current investigation found that polylactic acid with 1% of copper nanoparticles additives was up to 99.99% effective against _Staphylococcus aureus_ and _Escherichia coli_ after a 24-h incubation period. Nanoparticles of copper are preferable over silver due to the lower cost of copper and the reported side effects of using silver nanoparticles including local skin irritation, discoloration, or staining [13]. 3D printed antibacterial filaments also provide the possibility of developing antibacterial surgical instruments. A previous investigation [28] used polylactic acid filaments to develop a low cost Army/Navy retractor strong enough to be used in the operating room (75% infill was capable of supporting 13.6 kg before fracture). Polylactic acid has been shown to be a safe and suitable material for use in surgical instruments [28]. Polylactic acid is extruded at temperatures well above the 121 \({}^{\circ}\)C recommended for steam sterilization or even the 170 \({}^{\circ}\)C recommended for dry heat sterilization. However, other sterilization methods, such as autoclaving, compromise the structural integrity of polylactic acid, limiting the use of these devices in surgery [28]. Although lower temperature methods of sterilization, such as ethylene oxide \"gas\" sterilization, do not impact the strength of polylactic acid, the high levels of ethylene oxide residue produced in this process are a serious concern [28]. The hypoallergenic and safe nature of polylactic acid has been previously verified by the U.S. Food and Drug Administration and approved as a semi-permanent dermal filler and suture material [28; 29]. Therefore, the development of a polylactic acid 3D printing filament with antibacterial properties has several impactful medical applications and could revolutionize the manufacture of medical devices associated with bacterial development. The present investigation used PLACTIVETM 3D printing filaments that combine the versatility of polylactic acid and the high antibacterial properties of copper nanoparticles to develop antibacterial, thermoforming, and functional 3D printed finger prostheses. The increase in manual gross dexterity and high patient satisfaction scores after using the 3D printed partial finger prosthesis suggest that the finger prosthesis was functional, easy to use, comfortable, and effective (Table 2).