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Mancilla-De-la-Cruz, et al.
Table 5. Characteristics and challenges of stereolithography (SLA)
Characteristics Challenges
Method The resin vat contains a build platform. A single point laser Post-processing with UV-curing could be
located inside the machine maps selectively a light solidifying unsuitable for the APIs .
[16]
the liquid material [10,16] . The instruments are expensive .
[16]
Usually, the products are post-cured by UV light to improve The post-curing steps for render biocompatible
their mechanical properties . material can result in a loss of drug loaded and
[16]
Inverted SLA uses the light under transparent bottom of a resin subsequent imprecise dosing .
[12]
tank . The residual resin can represent a toxicity
[10]
SLA can print porous infill, such as QuickCast, from 3D risk .
[11]
systems. To modify the porosity of some tablets, it is necessary
to change their geometry, because the objects that are printed
with this method have a solid filling .
[10]
Material SLA uses photoreactive and photocurable materials . SLA has been limited by photopolymerizable
[12]
The drugs can be loaded directly into the liquid pre-polymer materials that would be biocompatible and
solution depending on its solubility . approved for human use .
[12]
[16]
SLA that works with multiples materials,
such as polymer mixtures and drug loaded
structures, is limited .
[16]
Quality High accuracy and resolution that allows fabrication of
personalized organic shapes for controlling drugs release
kinetics [12,16] .
An example is ProX/Project printer made by 3D Systems
Company (US). This printer has a layer thickness of
20 – 150 μm and has a resolution of 50 μm .
[18]
Table 6. Characteristics and challenges of 2-photon polymerization (2PP)
Characteristics Challenges
Method The lasers provide femtosecond pulses, which induce a highly The post-curing steps may result in a loss of
localized chemical reaction, leading to polymerization of the drug loaded and imprecise dosing .
[12]
photosensitive material .
[19]
2PP requires multiple post-curing steps to make it
biocompatible .
[12]
This method can print highly personalized organic shapes,
which are critical for implants and transdermal delivery for
controlling drug release kinetics .
[12]
Material The medicine can be loaded directly into the liquid This process uses only photoreactive and
prepolymer solution, depending on its solubility . photocurable materials .
[12]
[12]
2PP uses biocompatible photoinitiations or monomers . 2PP is not suitable for medications with
[12]
antioxidant properties, such as Vitamins A, C
and E, due to potential residual free radicals or
monomers .
[12]
Quality 2PP has a resolution in the nanometer range, and it is the vat
photopolymerization process with the best resolution .
[12]
Nanoscribe (Germany) created the Photonic Professional GT
printer, which works with a layer thickness of <1 μm and has
a resolution of 0.15 μm .
[18]
Previous tables have shown main characteristics advantages and disadvantages of methods as well as
of material jetting (MJ), binder jetting (BJ), filament materials and product quality of each technique. In the
extrusion, syringe extrusion, stereolithography (SLA), next section, specific materials for 3D printing drug
2PP, DLP, and selective laser sintering (SLS), including delivery will be discussed.

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