This document discusses diffusion principles that are important in biological systems and pharmaceutical sciences. It defines diffusion as the net movement of molecules from an area of high concentration to low concentration down a concentration gradient. The document outlines different types of diffusion including passive, facilitated, active, and filtration. It also describes Fick's Laws of Diffusion, which state that the rate of diffusion is proportional to the concentration gradient. Fick's laws are applied to understand processes like drug release from dosage forms and distribution in tissues.

1. DIFFUSION PRINCIPLES
SOLUBILITY PHYSICAL PHARMACEUTICS-I
DIFFUSION PRINCIPLES IN BIOLOGICAL SYSTEMS

2. DIFFUSION
 “ A physical process that
refers to the net
movement of molecules
from a region of high
concentration to lower
concentration under the
influence of
concentration gradient.”

3. DIFFUSION
 “Mass transfer of
individual molecules of
a substance caused by
random molecular
motion, associated with
a driving force such as
the concentration
gradient”

4. USE OF DIFFUSION CONCEPT
 Diffusion phenomena applied in pharmaceutical
sciences include:
 1. Release of drug from dosage form
 2. Ultrafiltration, microfiltration, dialysis,
hemodailysis.
 3. Permeation & distribution of drug in living tissues
 4. Estimation of molecular weight of polymers
 5. Prediction of absorption & elimination of drug.

5. USE OF DIFFUSION CONCEPT

6. TYPES OF DIFFUSION
 1. Passive diffusion:
 Net moment of material from an
area of high concentration to an
area of low concentration.
 The difference between high and
low concentration is termed as
concentration gradient.
 Diffusion will continue until the
gradient has been eliminated.

7. TYPES OF DIFFUSION
 1. Passive diffusion:
 It is the most important
mechanism for passage of drugs
through membranes.
 When drug release in body after
that it start to diffuse in region of
higher concentration to lower
concentration across the plasma
membrane of the cell.

8. TYPES OF DIFFUSION
 2. Facilitated (carrier
mediated) diffusion:
 It is moment of
molecules across the
cell membrane via
special transport
proteins that are
embedded within the
cellular membrane.

9. TYPES OF DIFFUSION
 3. Active transport:
 Movement of
molecules across a
membrane from a
region of lower
concentration to higher
concentration, against
the concentration
gradient.

10. TYPES OF DIFFUSION
 4. Filtration:
 Movement of
solvent or
solute
molecules,
influenced by
hydraulic
pressure.

11. LAWS OF DIFFUSION
 It is Given by Adolf Fick in 1856.
 The simplest description of diffusion is
given by Fick's laws, which were developed
by Adolf Fick in the 19th century:
 The molar flux due to diffusion is
proportional to the concentration gradient
 1. FICK’S FIRST LAW OF DIFFUSION
 2. FICK’S SECOND LAW OF DIFFUSION:
Adolf Fick

12. FICK’S FIRST LAW OF DIFFUSION
 According to Fick’s law of
diffusion,
 “The molar flux due to diffusion
is proportional to the
concentration gradient”.
 The rate of change of
concentration of the solution at
a point in space is proportional
to the second derivative of
concentration with space.

13. FICK’S SECOND LAW OF DIFFUSION
 Prediction of change in
concentration along with
time due to diffusion.
 “Change in concentration
with time in a particular
region is proportional to the
change in concentration
gradient at that point in the
system.”

14. LAWS OF DIFFUSION
 The difference in the concentration of a
substance between two areas is called the
concentration gradient .
 The bigger the difference, the steeper the
concentration gradient and the faster the
molecules of a substance will diffuse.
 The direction of diffusion is said to be
'down' or 'with' the concentration gradient.

15. LAWS OF DIFFUSION APPLICATIONS
 Fick’s law is applicable for two miscible liquids when they
are brought in contact and diffusion takes place at a
macroscopic level.
 Pharmaceutical application in drug release and absorption
of medicine to provide pharmacological action
 Applications in food industries.
 Fabrication of semiconductor: Diffusion equations from
Fick’s law are used to fabricate integrated circuits.