Page 337 - IJB-8-4

Mancilla-De-la-Cruz, et al.
polymers degrade into the body over a specified time mesoporous structure, along with good bone-forming
period by either surface erosion, whereby the material bioactivity and enhanced mechanical strength in
degrades at the outermost surface of the polymer via comparison to polyurethane foams previously used . For
[27]
hydrolysis, or bulk erosion, whereby the polymer drug delivery purposes, bioceramic carriers are increasing
degrades evenly throughout the entire polymer bulk. its popularity. In fact, they have been considered a good
In contrast, non-biodegradable polymers retain their replacement for polymers, particularly for bone local
structural and chemical integrity throughout the intended drug applications and tissue regeneration. Bioceramic
life cycle. Examples of biodegradable polymers used in materials for drug delivery include tricalcium phosphate,
DDDs include poly(caprolactone), poly (trimethylene hydroxyapatite, and bioactive glass, among others. They
carbonate), poly(lactide), poly (vinyl alcohol), and exhibit unique characteristics; for example, bioactive
triethyl citrate (TEC), among others. Non-biodegradable glass is bioactive, osteoconductive and osteoinductive,
polymers include poly (ethylene glycol) and ethylene and has a good degradation rate [6,7,28] . Moreover, due to
vinyl acetate (EVA). Each polymer exhibits a particular the unique characteristics of mesoporous bioactive glass,
degradation rate, and therefore drug release profile, with such as large surface area, nanopore volume and nano-
an alteration to the polymers molecular weight throughout channel structure, it is frequently used for drug delivery
the synthesis process able to tailor this further to suit a as powders, fibers, disks, microspheres, MBG-polymer
particular printing technology (e.g., material jetting which composites, and 3D scaffolds .
[29]
requires low-viscosity polymer inks, or extrusion-based
methods which require more paste-like consistencies) 3.3. Hydrogels
or intended treatment dosage or administration time Hydrogels consist of water-soluble polymers that are
period [16,17] . cross-linked in a 3D network [10,30] . The potential to create
Polymers are quite attractive for 3D printed a hydrogel out of any water-soluble polymer results
drug delivery due to their distinctive capabilities for in them being considered an attractive alternative to
drug loading, drug release, biocompatibility, and polymeric materials in drug delivery applications as they
biodegradability. In particular, smart polymers have encompass a wide range of chemical compositions and,
attracted attention of the industry, as they are able to as a result, physical properties. These physical properties
deliver the drug at specific moments and places as a can be tailored in terms of porosity and material swelling,
response to physiological stimuli. Their main advantages which, in turn, allows the opportunity to control drug
lie in their versatility and tunable sensitivity while their diffusion out of the polymer matrix. Some examples of
main drawback is their slow response time. Despite this hydrogels used in drug delivery include alginates, fibrins,
disadvantage, they have a huge potential to deliver oral gelatine, and polyacrylamide . Of these, one of the most
[30]
drugs sensitive to both gastric acid and enteric enzymes cost-effective biomaterials is gelatin methacrylamide
as well as to make smart diagnostics . Polymers can be (GelMA) . In fact, gelatines have particular attributes
[24]
[26]
applied to both hydrophilic and hydrophobic drugs, which for drug delivery applications, which include higher
allow drug-controlled release in constant doses even over drug encapsulation efficiency, stable carrier and drug
long periods . There are different types of polymers. complexation, fewer side effects, lower systemic
[25]
One of the most common polymers is poly (vinyl alcohol), cytotoxicity, reduced immunogenicity, and prolonged
also designated as PVAL, which has good solubility in circulatory time .
[31]
water but not in ethanol nor in various organic diluents.
PVAL can be used to produce polymeric multiple-layered 4. 3D printing in pharmaceutical
material for 3D printing through IP technique, and by manufacturing
varying the molecular weight of PVAL, it is possible to
generate specific viscosity rates in combination with 3D The potential of parts with high geometric complexity,
models . precise dimensional accuracy, and multi-material
[26]
capabilities exhibited by various 3D printing processes
3.2. Glasses has seen a rapidly expanding surge of research over the
Glasses have shown potential in pharmaceutical past two decades, with oral, topical, rectal and vaginal,
applications, with their potential bioactivity allowing parenteral, and implantable DDDs among those reviewed
for interactions with living cells. Similar to polymeric to target a range of conditions. Some examples are shown
materials, glasses can be biodegradable or non- in Figure 6.
biodegradable, more or less brittle, and can be tailored to 4.1. Oral drug dosage form
exhibit customizable degradation rates. As an example,
mesoporous bioactive glass (Sr-MBG) containing Oral DDDs (ODDDs) such as tablets and capsules
strontium has shown sustained drug release due to its are arguably the most widely accepted method of drug

International Journal of Bioprinting (2022)–Volume 8, Issue 4 329