Hydrogels: Biomaterials for Sustained and Localized Drug Delivery
239
ii. Functional unit to regulate molecular interactions (Vander Waals forces,
hydrogen bonding, hydrophobic interactions, electrostatic interaction, π-π
interactions) that contribute to transitions in hydrogels.
Potential applications include PEG-based hydrogel microparticles for pulmonary
drug delivery, and peptide delivery of PEG incorporated Gly-Leu-Lys (GLK) by
overexpression of metalloproteinases [177].
One another major biological stimuli-responsive hydrogel is ‘glucose responsive hydrogel’ [101]. Insulin-dependent diabetes mellitus (IDDM), requires drug
release in response to the changes in physiological blood glucose concentration
[148]. Hydrogel designed to facilitate glucose-responsive mostly combines the use
of saccharide-lectin complex as a crosslinker, incorporation of glucose binding site
into a thermoresponsive polymer, utilizing enzymatic activity by the conjugating
enzyme to pH-responsive polymer [175].
6 Current Trends and Future Prospects
Hydrogel though widely studied, has less translational efficiency. The reasons
attributing to its limitation include reduced control over polymerization rate, weak
mechanical property, stability, and inertness in the in vivo physiological conditions.
Sterilization of mass production of the hydrogel, to withstand severe temperature
cycles without losing its intended property is a significant challenge. Any biomaterial
research is carried out to reach for clinical translation ultimately. Multiple problems
arise for hydrogel formulation, storage, regulatory complexity, and cost are yet to
be needed to overrun by researchers, to obtain robust data before clinical trials. As
hydration is a typical mechanism involved, thus terminal sterilization is complicated
to make it step-by-step validation from raw material to complete fabrication. Degradation or deterioration of the drug-polymer complex can occur during premature
hydrolysis, calling out for optimum storage conditions. Regulatory approvals of the
hydrogel drug systems also present a significant concern.
Stimuli-responsive polymers will have to stride through upfront challenges, such
as availability of limited functional monomers, low binding capacity, template
leakage, and small target intended delivery due to reduced recognition of particular
site and cell surface receptors [153].
Current HNC development involves optimization of stimuli responsiveness for the improvement of mechanical strength and biodegradation. It
mainly depends upon the embedded NPs in the polymeric networks for
pH/enzyme/ion/temperature/magnetic/electric field responsiveness. HNCs also have
embarked on its frontier in mimicking native tissues by multiphase combination.
Concerning nanoparticle synthesis, biogenic sources such as plants, bacteria, yeast,
fungi, and physical/chemical methods would be favorable. The organic, eco-friendly
manner of NPs synthesis is yet to be achieved [154].
239
ii. Functional unit to regulate molecular interactions (Vander Waals forces,
hydrogen bonding, hydrophobic interactions, electrostatic interaction, π-π
interactions) that contribute to transitions in hydrogels.
Potential applications include PEG-based hydrogel microparticles for pulmonary
drug delivery, and peptide delivery of PEG incorporated Gly-Leu-Lys (GLK) by
overexpression of metalloproteinases [177].
One another major biological stimuli-responsive hydrogel is ‘glucose responsive hydrogel’ [101]. Insulin-dependent diabetes mellitus (IDDM), requires drug
release in response to the changes in physiological blood glucose concentration
[148]. Hydrogel designed to facilitate glucose-responsive mostly combines the use
of saccharide-lectin complex as a crosslinker, incorporation of glucose binding site
into a thermoresponsive polymer, utilizing enzymatic activity by the conjugating
enzyme to pH-responsive polymer [175].
6 Current Trends and Future Prospects
Hydrogel though widely studied, has less translational efficiency. The reasons
attributing to its limitation include reduced control over polymerization rate, weak
mechanical property, stability, and inertness in the in vivo physiological conditions.
Sterilization of mass production of the hydrogel, to withstand severe temperature
cycles without losing its intended property is a significant challenge. Any biomaterial
research is carried out to reach for clinical translation ultimately. Multiple problems
arise for hydrogel formulation, storage, regulatory complexity, and cost are yet to
be needed to overrun by researchers, to obtain robust data before clinical trials. As
hydration is a typical mechanism involved, thus terminal sterilization is complicated
to make it step-by-step validation from raw material to complete fabrication. Degradation or deterioration of the drug-polymer complex can occur during premature
hydrolysis, calling out for optimum storage conditions. Regulatory approvals of the
hydrogel drug systems also present a significant concern.
Stimuli-responsive polymers will have to stride through upfront challenges, such
as availability of limited functional monomers, low binding capacity, template
leakage, and small target intended delivery due to reduced recognition of particular
site and cell surface receptors [153].
Current HNC development involves optimization of stimuli responsiveness for the improvement of mechanical strength and biodegradation. It
mainly depends upon the embedded NPs in the polymeric networks for
pH/enzyme/ion/temperature/magnetic/electric field responsiveness. HNCs also have
embarked on its frontier in mimicking native tissues by multiphase combination.
Concerning nanoparticle synthesis, biogenic sources such as plants, bacteria, yeast,
fungi, and physical/chemical methods would be favorable. The organic, eco-friendly
manner of NPs synthesis is yet to be achieved [154].