Hydrogels are highly absorbent polymeric networks capable of retaining large quantities of water, making them suitable for drug delivery applications. They can be classified by their preparation method and cross-linking type, and their properties such as biocompatibility, swelling behavior, and mechanical strength are crucial for effective drug delivery systems. Applications of hydrogels span various administration routes, including peroral, rectal, ocular, and transdermal, and ongoing advancements in polymer technology continue to enhance their functionality in biomedical fields.

1. Hydrogels based Drug
Delivery System
By: Abdul Rafay Ahmad
MSPH-F20-009
M.Phil Pharmaceutics
Mentor: Dr Rashida Parveen

2. Definition:
› “Hydrogels are polymeric networks that take in and keep huge
quantities of water. There are hydrophilic groups in the
polymeric network which become hydrated in aqueous media
thus forming hydrogel structure.”
› Hydrogels are highly absorbent (they can contain over 90%
water) natural or synthetic polymeric networks.
› Hydrogels also possess a degree of flexibility very similar to
natural tissue, due to their significant water content

3. Characteristics Of Hydrogels:
 Both solid like and liquid like properties
 High biocompatibility
 Can trap large quantity of water in the network structure (“hydro”)
 Shrink when dried
 Environmental stimuli respondent

4. Classification:
› On the basis of Preparation:
1- homo-polymer
2- copolymer
3- Semi-interpenetrating network
4- interpenetrating network
› On the basis of cross linking:
1- Chemical hydrogels
2- Physical hydrogels

5. Homo-Polymer:
› Derived from single species of monomer.
› Cross linked homopolymers are used in drug delivery system
and in contact lenses.
› Polyethylene glycol (PEG) based hydrogels are responsive
towards external stimuli and hence these smart hydrogels are
widely used in drug delivery system

6. Co-polymeric hydrogel
› Composed of two types of monomer in which at least one is
hydrophilic in nature
› Synthesized the biodegradable triblock poly(ethylene glycol)-
poly(caprolactone)- poly(ethylene glycol) (PEG) co-polymeric
hydrogel for the development of drug delivery system.
› The mechanism involve here is the ring-opening
copolymerization of caprolactone (Nylon 6)

7. Semi- Inter Penetrating Network (Semi-IPN):
› If one polymer is linear and penetrates another cross-linked network without
any other chemical bonds between them, it is called a semi-inter penetrating
network.
› Semi-IPNs can more effectively preserve rapid kinetic response rates to pH or
temperature due to the absence of restricting interpenetrating elastic network.
› Provides benefits like modified pore size & slow drug release etc.
› This pH sensitive semi-IPN was synthesized by co-polymerization in the
presence of N, N′-methylene bis-acrylamide as a cross-linking agent.
› The network contained both covalent and ionic bonds.
› The covalent bonds retained the 3-D structure of hydrogel and the ionic bonds
imparted the hydrogel with higher mechanical strength and pH responsive
reversibility

8. Inter Penetrating Network (IPN):
› It’s an intimate combination of two polymers, at least one of which is
synthesized or cross-linked in the immediate presence of the other.
› This is typically done by immersing a pre-polymerized hydrogel into
a solution of monomers and a polymerization initiator.
› IPN method can overcome thermodynamic incompatibility
occurring due to the permanent interlocking of network segments
and limited phase separation can be obtained.
› The main advantages of IPNs are relatively dense hydrogel matrices
can be produced which feature stiffer and tougher mechanical
properties, controllable physical properties and more efficient drug
loading compared to other hydrogels.

9. Properties of Hydrogels:
› Swelling property: hydrogels are the swollen polymeric
networks, interior of which is occupied by drug molecules,
therefore, release studies are carried out to understand the
mechanism of release over a period of application
› Swelling property is influenced by:
• Type and composition of monomers
• Other environmental factors such as : temperature, pH, ionic
strength
• Cross-linking (mechanical strength and permeability)

10. Continued…
› Mechanical properties: These are very important for pharmaceutical
applications. For example property of maintaining its physical texture during the
application of drug delivery.
- Changing the degree of crosslinking has been utilized to achieve the desired
mechanical property of the hydrogel.
› Biocompatible properties: It is important for the hydrogels to be biocompatible
and nontoxic in order to make it applicable in biomedical field.
- Cell culture methods, also known as cytotoxicity tests, can be used to evaluate
the toxicity of hydrogels.

11. Applications of Hydrogels in Drug Delivery:
› Benefits of controlled drug delivery
• More effective therapies with reduced side effects
• Numerous applications Stem Cells, Tissue Engineering, Cell Therapy,
Contact Lenses and Cancer Treatment.
• The maintenance of effective drug concentration levels in the blood
• Patient’s convenience as medicines hence increased patient compliance

12. Continued…
› Hydrogels that are responsive to specific molecules, such as
glucose or antigens, can be used as biosensors as well as drug
delivery systems.
› Sensitive hydrogels like temperature, pH sensitive, which are
used for the targeted delivery of proteins to colon, and
chemotherapeutic agents to tumours.

13. Advantages of Hydrogels:
› Hydrogels possess a degree of flexibility very similar to natural
tissue, due to their significant water content.
› Entrapment of microbial cells within Hydrogel beads has the
advantage of low toxicity.
› Environmentally sensitive Hydrogels have the ability to sense
changes of pH, temperature, or the concentration of metabolite
and release their load as result of such a change.
› Timed release of growth factors and other nutrients to ensure
proper tissue growth.

14. .
› Hydrogels have good transport properties.
› Hydrogels are Biocompatible.
› Hydrogels can be injected.
› Hydrogels are easy to modify.

15. Disadvantages of Hydrogels:
› Hydrogels are expensive.
› Hydrogels causes sensation felt by movement of the maggots.
› Hydrogels causes thrombosis at Anastomosis sites.
› The surgical risk associated with the device implantation and
retrieval.
› Hydrogels are non-adherent; they may need to be secured by a
secondary dressing.

16. .
› Hydrogels used as contact lenses causes lens deposition,
hypoxia, dehydration and red eye reactions.
› Hydrogels have low mechanical strength.
› Difficulty in handling, loading and Sterilization.

17. APPLICATIONS OF HYDROGELS IN DRUG
DLEIVERY:
› A number of strategies have been proposed to achieve drug
delivery systems for efficient therapy.
› Among them, hydrogels have attracted considerable attention
as excellent candidates for controlled release devices, bio
adhesive devices, or targetable devices of therapeutic agents.

18. 1- Peroral drug delivery:
› Drug delivery through the oral route has been the most common
method in the pharmaceutical applications of hydrogels.
› In peroral administration, hydrogels can deliver drugs to four
major specific sites; mouth, stomach, small intestine and colon.
› By controlling their swelling properties or bio adhesive
characteristics in the presence of a biological fluid, hydrogels can
be a useful device for releasing drugs in a controlled manner at
these desired sites. Additionally, they can also adhere to certain
specific regions in the oral pathway, leading to a locally
increased drug concentration, and thus, enhancing the drug
absorption at the release site

19. A- Drug delivery in the oral cavity :
› Drug delivery to the oral cavity can have versatile applications
in local treatment of diseases of the mouth, such as
periodontal disease, stomatitis, fungal and viral infections,
and oral cavity cancers. Long-term adhesion of the drug
containing hydrogel against copious salivary flow, which
bathes the oral cavity mucosa, is required to achieve this local
drug delivery

20. B- Drug delivery in the GI Tract:
› The GI tract is unquestionably the most popular route of drug delivery
because of the facility of administration of drugs for compliant therapy, and
its large surface area for systemic absorption.
› It is, however, the most complex route, so that versatile approaches are
needed to deliver drugs for effective therapy. Like buccal delivery, hydrogel-
based devices can be designed to deliver drugs locally to the specific sites in
the GI tract. For example, stomach-specific antibiotic drug delivery systems
for the treatment of Helicobacter pylori infection in peptic ulcer disease. For
localized antibiotic delivery in the acidic environment of the stomach, they
developed cationic hydrogels with pH-sensitive swelling and drug release
properties. The hydrogels were composed of freeze-dried chitosan-poly
(ethylene oxide) (PEO) IPN. pH-dependent swelling properties and the
release of two common antibiotics, amoxicillin and metronidazole,

21. C- Rectal delivery:
› The rectal route has been used to deliver many types of drugs,
although patient acceptability is variable due to the discomfort
arising from administered dosage forms.
› Its primary applications have been for local treatment of
diseases associated with the rectum, such as haemorrhoids.
› Additionally, it is well known that drugs absorbed from the
lower part of the rectum drain into the systemic circulation
directly. Thus, the rectal route is a useful administration route
for drugs suffering heavy first-pass metabolism. Conventional

22. D- Ocular delivery
› In ocular drug delivery, many physiological constraints prevent
a successful drug delivery to the eye due to its protective
mechanisms, such as effective tear drainage, blinking and low
permeability of the cornea.
› Thus, conventional eye drops containing a drug solution tend
to be eliminated rapidly from the eye, and the drugs
administered exhibit limited absorption, leading to poor
ophthalmic bioavailability.

23. Transdermal delivery:
› Drug delivery to the skin has been traditionally conducted for
topical use of dermatological drugs to treat skin diseases, or for
disinfection of the skin itself. In recent years, a transdermal
route has been considered as a possible site for the systemic
delivery of drugs. The possible benefits of transdermal drug
delivery include that drugs can be delivered for a long duration
at a constant rate

24. Conclusion:
› Recent developments in polymer technology has led to the
development of various stimuli sensitive hydrogels like pH,
temperature sensitive hydrogels
› A new way to create hydrogels has been developed by immobilizing
different proteins at the same time.
› Hydrogels with novel properties will continue to play important role
in drug delivery.
› New synthetic methods have been used to prepare homo- and co-
polymeric hydrogels for a wide range of drugs, peptides, and protein
delivery applications.
› Hydrogels are also used in regenerating human tissue cells