PLGA is a biodegradable and FDA-approved copolymer of poly lactic acid and poly glycolic acid. It is commonly used as a carrier for drug delivery due to its biodegradability and ability to tune degradation kinetics by adjusting the lactic acid to glycolic acid ratio. The document discusses the types of biodegradable polymers including synthetic polymers like PLGA and natural polymers. It explains that PLGA degradation is dependent on hydrolysis and factors like crystallinity and molecular weight that influence properties. The pharmacokinetics of PLGA is non-linear and dose-dependent, and PLGA has been shown to accumulate in organs like the liver and spleen. Surface modification with polymers like PEG can

1. Biodegradable
carrier
PLGA
Poly Lactic-co-Glycolic Acid
1

2. 2

3. Biodegradable Polymers
are natural or synthetic
in origin and
are degraded in vivo, either
enzymatically or non-
enzymatically or both .
not an intrinsic
property of a material,
drug-
polymer-tissue interactions
Synthetic biodegradable polymers
Hydroxy acids (a family that includes polylactic-
co-glycolic acid, PLGA), polyanhydrides
Naturally occurring polymers
such as complex sugars (hyaluronan, chitosan)
and inorganics (hydroxyapatite)
3

4. poly
lactic-co-glycolic acid (PLGA)
FDA-approved
biodegradable polymers
delivery
vehicles drugs proteins
DNA,RNA and peptides
4
PLGA
popular
tune the overall
physical properties
controlling the
relevant parameters to achieve a
desired dosage.

5. PLGA is a Copolymer of Poly lactic
acid (PLA) + poly glycolic acid
(PGA)
Poly Lactic acid has an Asymmetric carbon .Typically described D or L as ( PDLA)/
(PLLA) *
Generally PLGA contains poly D,L lactic acid -co- glycotic acid where D and L forms
are in equal ratio.
!
Hydrolysis
of ester
bond in
water
Presence of methyl side groups in PLA :
1) makes it more hydrophobic than PGA
2) so lactide rich PLGA copolymers are
less hydrophilic,
3) absorb less water
4) subsequently degrade more slowly

6. PC Ps
6
PLGA
is soluble in wide range
of common solvents
including chlorinated
solvents,
tetrahydofuran,
acetone or ethyl
acetate

7. influences
Due To Hydrolysis of
PLGA
which is dependent
on the type and
molar ratio of the
individual monomer
components (PLA ,
PGA)
by the degree of
crystallinity of the
PLGA,
Mechanical strength,
swelling behavior,
capacity to undergo
hydrolysis and
biodegradation rate
of the polymer are
directly influenced
7

8. Degree of crystallinity and
melting point of the polymers
are directly related to the
molecular weight of the
polymer
Crystalline PGA, when
co-polymerized with
PLA, increase the rate of
hydration and hydrolysis
HOW ???
By reducing the
degree of
crystallinity and Tg (glass transition temperature) :
8

9. 9
Pharmacokinetics
and Bio-distribution
Profile
Therefore, design
essentials must
incorporate
mechanisms of
degradation and
clearance of the vehicle
as well as active
pharmaceutical
ingredients (API)
PLGA, must be able
to deliver:
its payload (drug)
with appropriate
duration,
biodistribution and
concentration for
the intended
therapeutic effect

10. “Biodistribution and pharmacokinetics of PLGA
follows a non-linear and dose-dependent profile
!!!!!!!!
10

11. FACT
Experiments indicate
that some
formulations of PLGA
accumulate rapidly in
• liver
• Peritoneal
macrophage
• Bone marrow
• Lymph nodes ,
spleen
• spleen

12. 12
To address these limitations:
studies have investigated
-)the role of surface modification,
By incorporation of surface
modifying agents … Blood
circulation half life increases .
The degradation of the PLGA
carriers is quick on the initial stage
(around 30%) and
slows eventually to be cleared by
respiration in the lung

13. PLGA
hydrophobic
- PEG
hydrophilic
Copolymers of PLGA
Block copolymer are
either :
1)Diblock copolymer
(PLGA-PEG)
2)Triblock copolymer
(PLGA-PEG-PLGA,
ABA) & (PEG-PLGA-
PEG, BAB)
13

14. Before continuing
What is
temperature
responsive
copolymers
Called Thermogel
Free flowing solution at low
temperature ??( H-bond between
hydrophilic segments & water
molecules dominates the aqueous
solution , resulting in dissolution
in water ( liquid form).
highly viscous at body
temp(higher temp)??? .(H-bond
becomes weaker & hydrophobic
forces among PLGA segments are
strengthened , forming solution-
gel transition.

15. Diblock copolymer Triblock copolymer
PEG chains orient themselves towards the external
aqueous phase in micelles ,surrounding the
encapsulated species
Hydrophobic PLGA form associative crosslinks &
hydrophilic PEG allow the copolymer molecule to stay
in solution.
PEG layer act as barrier , reducing interaction with
foreign molecules by steric & hydrated repulsion ,
enhancing shelf stability
Temperature responsive copolymers . ABA & BAB
are thermogel , free flowing solution at low temp. &
high viscous at body temp .
Yet , addition of PEG reduces encapsulation
efficiency for drugs. The exact mechanism is unclear
however that could be because steric interference of
drug-polymer interaction by PEG chains.
Drug release from both ABA & BAB by 2 mech. :
1)Drug diffuse from hydrogel during the initial release
phase
2)Erosion of hydogel matrix in later phase
shows better release kinetics from formulation than
PLGA alone
During degradation of BAB :
there is mass loss of PEG-rich components ,that
increasing hydrophobicity of remaining gel
( causing less water content )
Copolymers
15
That can be applied to other
copolymer combinations , eg.
PLGA & polycaprolactone

16. “To Sum up
1) What are the types of polymers
2) What is PLGA
3) What does the methyl grp in PLA Does
4) What happen to the formulation parameters due to hydrolysis of PLGA
5) What do the physical properties depend on
6) higher content of PGA leads to
7) PK And BD of PLGA follows what profile
8) PLGA Accumulate in
9) What is the role of surface modification
10) What are the types of copolymers
11) Compare between bi/triblock copolymers
16

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