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Custodio, et al.
monomer resin. The liquid resin solidifies on exposure to as possible. The human bone has stiffness in the range
a CAD-guided incident light . SLS traces a CAD pattern of 17–20 GPa. The integration of hard HAp ceramics
[8]
using a laser beam onto the powder resin, thus selectively and polymeric PLA matrix allows for bone substitute
sintering the powders into a solid object . FDM materials that are flexible and strong .
[14]
[9]
extrudes a thermoplastic filament into built materials and Injection-molded PLA/HAp bioactive composites
support structures layer by layer . Current commodity have been fabricated to be used as an internal fixation
[10]
thermoplastic filaments that are suitable for FDM printing device for cancellous bone regeneration . Micro and
[15]
include polypropylene, acrylonitrile butadiene styrene, nanoscale-HAp particles have been incorporated to
polystyrene, polyvinyl alcohol, polyamide (PA or nylon), PLA through electrospinning. Both micro-HAp and
and polylactic acid (PLA). nano-HAp have shown to improve the elastic modulus
PLA has been a common filament for FDM of the electrospun mats and acted as nucleating agents.
3D printing, mainly because of its relatively lower However, micro-HAp induced brittleness due to the
processing temperature, dimensional reliability, bigger geometry of the fillers which acted as defects
acceptable print quality, and good mechanical rather than as reinforcements . A study on 3D printed
[13]
performance. Its monomer, lactic acid, is produced PLA scaffolds varied the printing orientations (0°, 45°,
by fermenting dextrose derived from renewable crop and 90°), followed by surface modification using HAp.
resources such as corn, starch, and sugarcane. Hence, The resulting scaffolds’ compressive properties and cell
PLA is widely known as a sustainable, non-toxic proliferation were observed. It was found that the optimal
biocompatible, and biodegrading material. To date, printing orientation was 90° as it produced the highest
PLA is often used for biomedical applications, such as compressive strength (53 MPa), while no cell deaths were
bone tissue engineering , scaffolds [12] , and implants observed and all live cells have attached to the scaffold
[11]
fabrication. PLA-based implants benefit from the surface, thus ensuring the non-toxicity of the HAp-
[12]
avoidance of stress shielding effects, which is a known modified 3D printed PLA scaffolds .
disadvantage for metal implants. While implanted inside In this study, Hap-reinforced PLA matrix
the body, PLA would also dissolve naturally and is biocomposites have been fabricated to determine the
susceptible to biodegradation, and their by-products are effects of HAp powder loading to the physicochemical
non-toxic. Although plates and screws made from PLA and mechanical properties of the resulting 3D
have been used to fixate jaw fractures without additional printed composite (Figure 1). From locally sourced
support, PLA still has some inherent drawbacks and nanoprecipitated calcium carbonate (NPCC), as-
limitations. As compared to more popular bone implant synthesized HAp powders were mechanically mixed with
materials such as stainless steel and alloy metals, PLA PLA at different powder loadings, followed by extrusion
is comparatively inferior by a large margin in terms of into a filament, and lastly 3D printed. The effect of the
mechanical performance. Another difficulty of using PLA/Hap composition on the crystallinity, morphology,
pure PLA is the poor cell attachment and proliferation and mechanical properties was investigated.
on the polymer’s surface. To address these concerns,
the physicochemical properties of pure PLA can be 2. Materials and methods
altered and improved by incorporating biocompatible 2.1. Materials
ceramic fillers and reinforcements.
Ceramic materials, such as calcium phosphates, NPCC was locally sourced from the Philippines. PLA
silica, and alumina, comprise the human bone tissue. Due pellets (PLA, NatureWorks LLC, IngeoTM Biopolymer
to their biocompatibility, these ceramic compounds have 2003D) were purchased from D&L Polymers & Colors,
been synthesized and used as implants for biomedical Inc. The following chemicals: Phosphoric acid (H PO ,
3
4
applications. Bioactive implants are often coated with RCI Labscan Ltd.), ammonium hydroxide (NH OH,
4
a type of calcium phosphate called hydroxyapatite Loba Chemie Pvt. Ltd.), and ethanol (CH CH OH,
2
3
(HAp, Ca (PO ) (OH) ), a promising bone substitute Thermo Fisher Scientific), were used without further
4 6
10
2
mineral. However, HAp is neither used for load-bearing purifications. Distilled water was used in preparing the
applications nor in its bulk form due to its inherent solutions and for the washing procedures.
brittleness. Therefore, HAp is mostly used as surface 2.2. Hydroxyapatite synthesis
coating for other biomaterials dedicated for bone grafting.
As a filler or reinforcing material, HAp can act to improve Chemical precipitation technique was undertaken using
the matrix material’s biocompatibility , stimulate bone aqueous solution of calcium hydroxide, Ca(OH) and
[13]
2
regeneration, and improve the stiffness, compressive, and H PO . Before synthesis, Ca(OH) was prepared from the
4
3
2
bending strengths . Artificial implants should mimic calcination of NPCC to decompose CaCO into CaO and O
[14]
3
2
the mechanical properties of the natural bone as close (Eq. 2.1). This was followed by slaking to convert CaO into
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