surfactants

surface active agents amphiphilic in nature

hydrophilic region

hydrophobic head

lowers the interfacial tension
between phases enables interaction

Wetting

the extent to which a solid
will physically interact with a liquid

low = good wettability <60

high = poor wettability > 90

emulsion formation

spontaneous

concentration that micelles form
to attain minimum free energy state

too much surfactant requires energy
to keep all in a solution
thus to lower energy form micelle
= Entropic Effect

More surfactant= less surface tension

hydrophobic groups withdrawing
form the aqueous phase

surfactant associating to itself
encapsulating and forming a sphere

hydrophobic core

hydrophilic shells

drug delivery for hydrophobic materials

shape

depend upon surfactant's molecular geometry

mostly affected by hydrophobic
region and any steric interactions

increase in hydrophobic chain

low CMC

bigger size

nonionic surfactants = lower cmc= larger micelle

lower the interfacial tension between
the phases (oil and water) blending
enable interaction of two phase

wetting

miceller formation

emulsion formation

surfactant reduces surface tension

surface tension

at the surface particle are not completely surrounded
which results in a net inward force attraction exerted on
molecules at the surface by the molecules in the bulk solution

thus liquid surface contracts and
form a sphere spontaneously

contracted surface = minimum free energy

surface activity

amphiphilic orientation to remove the
hydrophobic group from the aq. environment

lowering the surface tension

this is to achieve minimum energy state

liposomes

antibodies

reaction with antibodies to be
phagocytize into the liver and
spleen allowing for passive targeting
of these sites

IM/ Subq: liposome get into the lymphatic system;
vaccine delivery

surfactants

antibacterial

cationic and ionic absorb onto bacteria surface
--> leaking of lipid cell membrane--> bacterial death

nonionic often aid in bacterial growth

lung surfactant

covers the surface of alveoli contacted with air

decreasing the surface tension

prevents collapse of alveoli

decreases pressure inside alveoli

premature infant have not enough lung surfactant= death

Anionic

negative charge

caboxylate

sulfate

sulfonate

phosphate

most widely used class

wetting agent

emulsifying agent

most common surfactant

above the pKa will ionize

in a basic solution acid are negatively charge

if the counter ion are sodium or potassium= water soluble

if countering are mono valiant most likely not soluble

Cationic

positive charge

nitrogen atom

amines

ph depended

quaternary ammonium

retains charge
over the entire pH range

function in protonated state

Benzylalkonium chloride
( BAC/BAK)

Zwitterionic

example

isoelectric point

positive charge

ammonium group

negative charge

carboxylate

both positive and negative
charges upon full ionization

behave similar to nonionic surfactant

non ionic

no charge

good compatibitlity

stability

may be water soluble or insoluble
depending on functional group

water soluble

polyoxyethylene groups

water insoluble

fatty alcohols

glycerol esters

fatty acid

poor as a surfactant

hydrophilic-lipophilic balance

8-18 O/W

3-6 W/O

7-9 surfactant act as wetting agent

surfactant as emulsifying agent 8-18

**emulsifier must be more
soluble in continuous phase

higher HLB= more hydrophilic

low HLB= more lipophilic

HLBmix= Fa(HLBa)+Fb(HLBb)

HLB

solubilizing agent 15-18

detergents 13-15

o/w emulsifying agents 8-16

wetting and spreading agents 7-9

w/o emulsifying agents 3-6

Antifoaming agent 2-3

classified based on their
size and the number of lamellae

SUV
small unilamellar vesicles

LUV
Large unilamellar vesicles

MLV
multomellar vesicles

drug delivery for
both hydrophobic
and hydrophilic

issue

low stability in blood
and interstitial fluids

vesicle clearance rate

tissue distribution

good for antibodies and vaccination

two hydrophobic chains that
tends to form lamellar phase

form at an appropriate
lipid- to - water
ratio and temp

NOT spontaneous

via: signification
homogenization
ultrasonification

formed by phospholipids

aqueous core surrounded by
one or more bilayer membranes
alternating with
aqueous compartment