Biomedical Engineering Reference
In-Depth Information
or cells. These side reactions might induce immunogenicity and damage cells or
the efficacy of drugs. (5) Residual enzyme after enzymatic crosslinking also can
provide unexpected reactions with incorporated protein drugs. (6) Development
of various hydrogel-based drug delivery systems with non-modified original drug
is one of the best ways to produce the improved versions of biologics. Biobetters
can advance the efficacy, pharmacokinetic parameters, and safety profile of drugs
than original biologics or Biosimilars (subsequent versions of off-patent biolog-
ics with demonstrated physicochemical similarity). In addition, Biobetters can
also improve patient compliance due to a reduced rate of side effects and enhanced
convenience. (7) Sustained-release systems without initial burst release should be
considered. The charge interaction or the inclusion complex formation between
polymer and drug can improve these problems. (8) Incorporated drugs or cells
should be stable during the implantation period. Acidic degradation-products
released from polyester-based hydrogels raise the local acidity inside and around
the hydrogels, which lead an inflammatory response and a decrease of cell via-
bility or drug stability. (9) For tissue regeneration application, ECM mimicking
design of the hydrogel system is a key factor. Polypeptides have unique second-
ary structures of
ʱ
-helix, triple helix,
ʲ
-sheet, or random coil, etc. Different
combinations of polypeptide-based hydrogel systems allow various nanostruc-
tures in the hydrogels that affect proliferation and/or differentiation of encapsu-
lated cells. (10) Duration of in situ formed hydrogels should be adjusted to match
with drug release profile or tissue regeneration rate. (11) Macromers should be
selected based on application route. NIPAAm copolymer has been used for “cell
sheet” (a tissue-like cellular monolayer) development that already showed suc-
cessful applications to human clinical studies. However, in vivo application of
PNIPAAm hydrogel still has limitation on the toxicity of the residual monomer.
(12) Gel modulus, degradability, functional groups can affect stem cell fate. Soft
gel improves neurogenesis or adipogenesis, while stiff gel enhances osteogenesis.
Degradable or non-degradable hydrogels induces osteogenesis or adipogenesis,
respectively. Phosphate groups or alkyl groups can stimulate osteogenesis or adi-
pogenesis, respectively.
Challenging design of hydrogels with these understands and considerations
about various hydrogel systems will advance the development of smart bioactive
in situ gelling hydrogels for specific biomedical applications.
Also, study of flow properties of liquids is important for pharmacists working in
the manufacture of several dosage forms, such as simple liquids, ointments, creams
and pastes. The flow behavior of liquids under applied stress is of great relevance in
the field of pharmacy. Flow properties are used as important quality control tools to
maintain the superiority of the product and reduce batch-to-batch variations.
The clinically approved systems by using Pluronics/alginate (Guardix-SG)
and chitosan/glycerol phosphate (BST-CarGel) based thermal gels are interest-
ing examples. Alginate and Pluronics form interpenetrating network (IPN) by
adding calcium salt, where it forms a temperature sensitive gelling system. The
system was successfully applied as an antiadhesive agent after the surgery. BST-
CarGel was applied for articular cartilage repair on the microfractured treatment.
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