Stress shielding refers to the reduction in bone density (osteopenia) as a result of removal of normal stress from the bone by an implant (for instance, the femoral component of a hip prosthesis). This is because by Wolff's law, bone in a healthy person or animal will remodel in response to the loads it is placed under. Therefore, if the loading on a bone decreases, the bone will become less dense and weaker because there is no stimulus for continued remodeling that is required to maintain bone mass.
Discussion on Topic: Tuesday; 14 January, 2014
Internet Survey: Wednesday to Friday; 15 to 17 January, 2014
Work Division: Saturday; 18 January, 2014
19th to 21nd January
Disscussion and Modification of Assignment: Wednesday to Saturday; 22 to 25 January, 2014
Preparation of Presentation: Friday to Sunday; 24-26th January, 2014
Also known as macro-molecules.
Biodegradation is the process of converting polymer material into
harmless, simple, gaseous products by the action of enzymes, microorganisms and water.
Biodegradable polymers degrade as a result of natural biological
processes, eliminating the need to create a disposal system which can
cause harm to our environment.
Mechanism Of Biodegradable Polymers
Need for Biodegradable polymer
Do not require a second surgery for removal
Avoid stress shielding
Offer tremendous potential as the basis for controlled drug
These are the polymers obtained from natural resources,
and are generally non-toxic.
Natural polymers are formed in nature during the growth
cycles of all organisms.
Eg : DEXTRAN
1) Readily & Abundantly Available.
2) Comparatively Inexpensive.
3) Non toxic products.
4) Can be modified to get semi synthetic forms.
Classification of Natural biodegradable polymers
(Based on Origin)
Eg: Cellulose, Starch,
Chitin is a macromolecule found in the shells
of crabs, lobsters, shrimps and insects
Chitosan is obtained by partial deacetylation
Chitin is insoluble in its native form but
chitosan, the partly deacetylated form, is
linear co-polymer of β(1-4) linked
glucosamine and N-acetyl-D-glucosamine.
EXTRACTION OF CHITOSAN
Dil. NaOH Deproteinization
0.5% KMnO4 and
Hot Conc. NaOH
Odorless, white or creamy-white powder
Chelates many transitional metal ions
Highly basic polysacharides
in acidic pH, it gets solubilized due to protonation of
free amino groups and the resultant soluble
polysaccharide is positively charged.
hydrophilic in nature thereby it has the ability to form
gels at acidic pH.
Degraded by lysozyme to it’s by products
glucosamine and n-acetyl glucosamine
Colon drug delivery:
making contact lens- optical clarity, sufficient optical
correction, gas permeability, particularly towards oxygen,
wettability and immunological compatibility.
antimicrobial and wound healing properties of chitosan
along with an excellent film capability make chitosan
suitable for development of ocular bandage lenses.
Degraded by microflora present in human colon which
supports colon drug delivery
Good film forming property and mucoadhesive property
Transdermal drug delivery:
Studies on propranolol hydrochloride (prop-HCl)
delivery systems using various chitosan membranes
with different crosslink densities as drug release
controlling membranes and chitosan gel as the drug
reservoir have been performed.
Chitosan gets protonated in acidic solution, so it binds
strongly to negatively charged cell surface making it
useful to formulate bioadhesive dosage forms.
Chitosans, typically isolated from the shell of shrimp,
has the ability to react with DNA and compact it to
produce a nanoparticle. Such nanoparticles are more
readily taken up by cells.
Others: nano band- aid,cosmetics, etc.
mucopolysacharide, occurring naturally in all
Can be several thousands of sugar long
One of most hydrophiic molecules, also
known as natural moisturizer
Generally found in sodium salt form i.e. as
BIOSYNTHESIS OF HA IN BACILLUS
UDP- glucoronic acid
•HA is naturally synthesized from addition of glucoronic acid
and N-acetylglucosamine to growing chain using their activated
nucleotide sugars. Hyaluronan synthase is the enzyme
STRUCTURE AND CHEMISTRY
Polysaccharide made up of largely repeating
The alternating disaccharide units are linked by
(1→4) inter glycosidic linkage.
Chains consist upto 30,000 repeating units so it has
high molecular weight range (1000 to 10,000,000
Biodegradable, biocompatible, non-toxic, nonimmunogenic, non-inflammatory, linear chain
very hydrophilic; it adsorbs water making it
readily soluble in water, and produces a gel
Its viscous solutions have most unusual rheological
properties (pseudoplasticity) and are exceedingly
To improve the mechanical properties and control the
degradation rate, HA can be chemically modified or
crosslinked to form a hydrogel
of the gel is dependent upon a number of factors
including the length of the chain, cross-linking, pH
They are used in the preparation of gels for
delivery of drugs to eye and installation into
Microparticulate HA carrier:
formulations (eg: protein drugs)
have been developed using spray-dried HA
microparticles which act as a protein reservoir
Also protects the drugs from denaturation and
increases their bioactivity
Ocular drug delivery:
viscosity and pseudoplastic behavior which provide
mucoadhesive property can increase the ocular
expression of CD-44 (cluster determinant 44)
and RHAMM (receptor for hyaluronate-mediated
motility) receptors by various tumour cells, which
are endogenous ligands for HA, makes this a good
candidate for drug targeting to cancer cells
nanocarrier composed of hyaluronic acid(HA)
and chitosan(CH) was reported to encapsulate
bovine serum albumin (BSA) and cyclosporine A
for the nasal delivery of macromolecules
Topical drug delivery:
hydration and film formation enhance the
permeability of the skin to topical drugs also
promotes drug retention and localization in the
HA has been used in tissue engineering for
the cartilage replacement in the joints
Used in cosmetics, skin care system, as anti
ageing therapy (antioxidant nature)
Gelatin is a natural water soluble functional polymer
(protein) that is derived by partial hydrolysis of collagen
(chief protein component in skin, bones and white
connective tissues of the animal body).
It is commonly used for pharmaceutical and medical
applications because of its biodegradability and
biocompatibility in physiological environments.
Gelatin does not occur free in nature, and derived from
chief protein component in skin, bones, hides, and white
connective tissues of the animal body is classiﬁed as a
Gelatin derived from an acid-treated precursor is
known as Type A and gelatin derived from an
alkali-treated process is known as Type B.
Results in a difference in isoelectric points, being
7 – 9 for gelatin type A and 4 – 5 for gelatin type
FEATURES OF GELATIN
Characteristic features of gelatin are the high content of
the amino acids glycine, proline (mainly as
hydroxyproline) and alanine.
Gelatin molecules contain repeating sequences of
glycine, proline and alanine amino acid triplets, which
are responsible for the triple helical structure of gelatin.
STRUCTURE OF GELATIN
The chemical structure of gelatin is what makes gelatin
water soluble; form digestible gels and films that are strong,
flexible, and transparent; and form a positive binding action
that is useful in food processing,pharmaceuticals,
photography,and paper production.
Tasteless and odorless
Vitreous, brittle solid, yellow colored
Moisture content: 8-13% ; Relative density of: 1.3-1.4
Formation of thermo-reversible gels in water: When
gelatin granules are soaked in cold water they hydrate
into discrete, swollen particles. On being warmed, these
swollen particles dissolve to form a solution.
Soluble in aqueous solutions of polyhydric alcohols such as glycerol and
Insoluble in less polar organic solvents such as benzene, acetone,
primary alcohols and dimethylformamide.
Gelatin stored in air-tight containers at room temperature remains
unchanged for long periods of time. When dry gelatin is heated above
45 C in air at relatively high humidity (above 60% RH) it gradually
loses its ability to swell and dissolve.
Sterile solutions of gelatin when stored cold are stable indefinitely; but
at elevated temperatures the solutions are susceptible to hydrolysis.
Gelatin is composed of 50.5% carbon, 6.8% hydrogen, 17% nitrogen
and 25.2% oxygen. It gives typical protein reactions and is hydrolyzed
by most proteolytic enzymes to yield its peptide or amino acid
APPLICATION OF GELATIN IN
AND DRUG DELIVERY
Two-Piece Hard Capsules
Soft Elastic Gelatin Capsules
As a binder in Tablet
Source of essential amino acids
Absorbable Gelatin Sponge
Gelatin as Nanoparticle.
Biodegradable polymers have received much more attention in
the last decades due their potential applications in the field of
Biodegradable polymers have been researched, but polymers
based on renewable sources (especially on starch) are most
It provides a drug at a constant controlled rate owes a prescribed
period of time; cell targeting, colon targeting and nasal drug
delivery system and also assist in gene therapy.
It would degrade into nontoxic, absorbable subunits which would
be subsequently metabolized and removed from the body.
Recently different studies have been reported concerning the use
of degradable polymers, especially with starch and aliphatic
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