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International Journal of Bioprinting 3D-printed bone scaffolds and biofilm formation

generally not affected. However, severe fractures exceeding lattice-based, TPMS, and auxetic bone scaffolds in one
the trauma critical size restrict the bone from self-healing, single setting. 5,9,10,14,16-19
especially if interventive support is not administered. The Several scaffold manufacturing techniques are
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treatment of bone fractures requires expensive treatments, subdivided into traditional and advanced methods. In light
such as bone implants (e.g., bone plate and ilizarov) for bone of the growing desire for patient-specific medical implants
fractures, and autografts, allografts, and xenograft for bone in the form of free-form complex porous structures, three-
defects. A 12-month treatment for a single hip fracture costs dimensional (3D) printing has stepped in as the preferred
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around $43,669 on average. The global market for bone method for fabricating scaffolds that satisfy the prevailing
fracture devices is forecasted to reach $22.3 billion in 2029. requirements. 3D printing is an advanced manufacturing
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This projection spurs the increasing need for faster and process able to manufacture 3D physical parts layer-
easier approaches aiming to further improve the patient’s upon-layer without the need for tooling or assembly. In
quality of life, reduce morbidity, and develop lower-cost tissue engineering, material extrusion techniques in 3D
devices. With this being said, developing patient-specific and printing have been shown to be exceptional in producing
lightweight intelligent devices capable of delivering adequate biocompatible and degradable scaffolds. 20,21 There has been
mechanical, biological, and chemical performances is one of intensive explorations with regard to the production of
the most sought-after strategies. To address these problems, medical implants using filament-based material extrusion
three major concepts, namely additive manufacturing due to low energy consumption, affordability, and
(AM), tissue engineering (TE), and design engineering, processability for a wide range of materials from metals to
are integrated to promote the development of feasible composites to ensure optimal functionality of scaffolds.
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solutions. Researchers in both academia and industry have The most used biopolymers in material extrusion of bone
been working on the development of the optimal bone scaffolds are polycaprolactone (PCL), polylactic acid
scaffold design, including lattice, triply periodic minimal (PLA), and polyglycolic acid (PGA). 23,24
surfaces (TPMS), and auxetic structures, which can deliver
the fastest and most efficient therapeutic outcomes without The biological and mechanical behaviors of bone
4,5
causing adverse effects. scaffolds have been extensively investigated. Different types
of scaffold designs and scaffold materials were developed
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Deng et al. presented a comparative study between to optimize their performance to achieve efficient
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four lattice porous scaffolds resulting in the diamond lattice osteointegration. In spite of their excellent behavior such
unit with the best bone growth effect. After manufacturing as osteoconductivity, osteointegration, biocompatibility,
Ti-6Al-4V TPMS gyroid scaffolds with different axial biodegradability, strength, and bioactivity, bone scaffolds
diameter ratios, Qin et al. found that the mechanical are prone to bacterial infections, necessitating additional
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properties of these scaffolds, equipped with adequate procedures such as administration of antibiotics.
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permeability and cell adhesion, aligned with the natural Bacterial colonization and biofilm formation are main
bone properties. In another study, Asbai-Ghoudan et al. challenges in orthopedic implants, which can lead to
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investigated the permeability of three TPMS structures of implant replacement. The bacterial biofilm is defined
Fisher-Koch, gyroid, and Schwarz primitive, which can as a structured community of bacteria that adheres to
be applied in various medical applications. Furthermore, surfaces and produces a slimy extracellular polymeric
meta-structures have gained a lot of attention due to their substance (EPS). The EPS consists of polysaccharides,
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excellent mechanical properties and ability to mimic a proteins, and DNA providing the bacteria with protection
number of biological tissues. In this regard, auxetics are against antibiotics and host-immune response. Yuan et
9,10
negative Poisson’s ratio (NPR) meta-structures that have al. investigated the suppression of bacterial infection in
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the ability to perform lateral expansion during stretching scaffolds by using tricalcium phosphate doped with metal
with equal and opposite shrinking when compressed. ions (e.g., silver or zinc), which are released in a long-term
In tissue engineering, auxetics have been developed fashion for antibacterial purposes. Other propounded
for various tissues such as bone scaffolds, cartilage strategies include the adoption of physical means such
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scaffolds, and several other medical applications. In the as heat and sound to create an environment unsuitable
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pursuit of achieving the optimal scaffold designs, several for bacterial growth. Given the increasing practice of
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comparisons between TPMS and lattice-based structures externally equipping scaffolds with antibacterial properties,
have been made. 13,14 Some authors have expanded it has dawned on many researchers to consider developing
TPMS structure application to auxetics, evaluating their tissue engineering scaffolds with inherent antibacterial
mechanical and conduction properties. Although these capabilities. Optimizing the geometrical design is an
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structures have been repetitively reviewed, discussed, and important process in tailoring the functionality of bone
compared, no effort has been made thus far to compare scaffolds. Nevertheless, the geometrical design of scaffolds
Volume 10 Issue 1 (2024) 325 https://doi.org/10.36922/ijb.1768