Everything

Lesson 1: Drug Delivery Methods + How to choose

Drug Delivery: administration of drugs through various routes to improve health

• drug dispersion + solubility

• drug formulation: what polymers

Conventional: controlled

• oral = sustained

• nasal = extended

• rectal = site specific

• injection = pulsatile

Oral (swallow): FPM

• can’t give it to unconscious patients

• low solubility/permeability

• degraded by GI enzymes

• irregular + food can mess w/ it

Buccal (dissolve in cheek)/Sublingual (dissolve under tongue): Bypass FPM

• if you swallow you don’t get the effect

• has to be small doses

• fast absorption

Rectal: Bypass FPM

• suppository (melty thing) or enema (liquid)

• degrade by bacteria

Intravenous: Bypass FPM

• 100% efficiency + fast

• Invasive + requires professional

• Needs to be sterile + correct amount (avoid toxicity)

• injection (bolus) or infusion (IV bag)

Subcutaneous (bolus under skin): Bypass FPM

• can self administrate

• slow + complete absorption

• max dose of 2ml

Intramuscular (bolus into muscle): Bypass FPM

• can self administrate

• larger volume than subcutaneous (more than 2 ml, faster too)

Inhaler: Bypass FPM

• gases are rapidly absorbed

• have to be below 0.5 um

Transdermal (absorb through skin): Bypass FPM

• local effect + easy

• have to be below 10 mg/ml or Mw < 1000 Da

• Low absorption sometimes, but it’s easy since it’s a patch

How should you choose which method for drug delivery?

• what physicochemical properties the drug has

  • Drug molecular size (mw)

  • Dose size

  • Half life

  • Chemical stability

  • Loss of biological activity in aqueous solution (does it dissolve in water)

• what effect you want the drug to have

  • Local: surface (topical/vaginal)

  • Systemic: everything that doesn’t diffuse from the skin

  • Immediate response (everything fast)

    • injection, inhalation, intramuscular, subcutaneous,

What affects the efficacy of the drug?

• Dosage

• How much was absorbed

• Distribution to site

• Rate/extent of elimination

Fastest to slowest:

• injection > inhaler > intramuscular > subcutaneous > buccal/sublingual > transdermal > oral

Pathway of drug trying to get into your blood stream and do its thing

• Drug delivery method

• Absorption

• Distribution to site

• Elimination

First Pass Metabolism (FPM): drug concentration significantly reduced before systemic circulation bc of GI and liver

• if you bypass = efficient

Lesson 2: Drug Solubility and Formulation

• how much it dissolves and should we make the drug

Since we’re made of like 73% water and our blood is 92% water

• hydrophilicity/hydrophobicity is important!

• we have a lot of water and our proteins are carbon so balance

Strongest dipole dipole bond is hydrogen bonding

London dispersion (van der waals)

• unequal distribution of electron = temporary induced dipole

• weak

Dipole moment is how uneven distribution it is == how polar it is

• if BIG it’s polar it’s soluble in water = better diffusion

• if SMALL it’s non polar it’s soluble in lipids

Proteins have both hydrophilic and hydrophobic parts

AA build up proteins

20 Amino Acids

• 9 hydrophobic

• 5 charged (3 positive, 2 negative)

• 6 polar but not charged

Hydrophobic: nonpolar into core = most important protein stability

H bonds (wanna form water): form water + helix + sheets

Dipole-dipole (polar interaction): polar side chains

Coulombic (ionic): salt bridges but pH/ionic strength breaks it

Van der Waals (small temporary dipole): important for hydrophobic core

Chemical, covalent (disulfide bond): not in everything

Thermodynamics:

Enthalpy: heat

• H = E + PV

• Positive = endothermic, negative exo

• heat of reaction = heat of

Entropy: disorder, if spontaneous +entropy

• positive = more disorder, negative = less disorder

Gibbs Free Energy: energy that can be used to do work

What causes a protein to form?

• nonpolar parts really do not like the water so they fold into a protein w/ nonpolar parts facing inwards to reduce free energy

• it’s favorable (spontaneous) for proteins to fold

• protein formation is exothermic and increases entropy

• ice melting is spontaneous and endothermic

• free energy o transfer from nonpolar solvent to water is proportional to hydrophobic surface area

Why does protein folding create MORE entropy?

• surrounding water molecules are NOT bonding to the nonpolar parts (icy)

Dissolution: How to dissolve something

1. Separate solute particles from intermolecular forces

2. Separate solvent particles + have void spaces big enough for solute molecule

   1. water has a high dielectric constant, so water is main solvent

3. Solute is put inside void space

   1. If spontaneous, work is negative

How to overcome IMFS (break up the solute-solute bonds): Thermal Energy

• if strength of interaction between solute-solute is bigger than kbT, it won’t dissolve

• Boiling point of liquid is proportional to temperature and pressure

Every way to Increase Solubility:

• Polarity: if same polarity, inc solubility

• More branch chains = inc solubility, straight = dec solubility

• Decrease molecular weight = inc solubility

• If structurally similar = inc solubility

• Crystal Structure: if more regular + uniformly packed = dec solubility

• Ionizable (gain/lose proton to become base/acid)

  • Apparent Solubility = unionized + ionized form

  • If ionized = inc solubility

• Cosolvent: added to solvent to inc solubility bc it is nonpolar so it lowers the polarity making the drug more easily dissolved

  • if not ionizable = hydrophobic = don’t react to pH

  • don’t mess with the drug, mess with the solvent (add co)

• Surfactant: molecules that make up micelle like structures

  • hydrophilic head, hydrophobic tail (dec surface tension)

  • drug can be carried inside

• Nanosizing: Make smaller = better dissolved

  • prevent sticking together by adding polymers to maintain SA to volume ratio

  • dissolution rate proportional to surface area in contact w/ solvent

• Salt formation: change pH = better dissolved

• Cocrystals: add w/ the drug (NOT changing the drug itself) by precipitation/grinding

Polymorph: Different structure of drug (salt, cocrystal,cosolvent) to make it more optimal for drug delivery

Lesson 3-4: Drug Release

What are the types of drug release?

• Immediate

• Delayed (tablets)

• Sustained (over EXTENDED time)

• Controlled (rate + location)

• Stimulus release (trigger)

• Targeted release (specific site)

How to control drug release:

How does reservoir work?

• Water gets in, dissolves drug, drug gets out

• Rate can be controlled by: dissolution profile or permeability of membrane

How does a diffusion drug release matrix work?

• release drug at certain rate

• Dependent on : porosity, swellability, dissolution rate

How does osmotic pressure work?

• Drug in reservoir and coated w/ semipermeable membrane

• Water diffuses into it and pushes drug through hole (oral)

Types of Solute Transport:

• passive = no energy

• diffusion: gradient, inc temp = move faster

• convection: depends on flow of carrier fluid

What dictates diffusion?

• intermolecular interactions between solute and solvent

• Concentration gradient

• Diffusional barrier

What is a diffusion coefficient: how fast it spreads out

• affected by differences in solute size, noncovalent interactions, temp, viscosity

• drag force from energy transferred by random collisions

Stokes Einstein Equation ****really important

• if assume solute is really small, assume it’s a sphere —> f = 6pi (n) (R)

• really important bc you can also find the radius (how big your particle is)

  

Fick’s 1st and 2nd Law

Steady state: dC/dt = 0

• change in concentration over change in time

Nonsteady state (not at equilibrium): dC/dt = changing

• means solute flux changes over time as drug reservoir is depleting

Permeability:

• partition constant dependent on ionicity or hydrophilicity

• Φ < 1: membrane surface concentration is less than solution

  • prefers to be in SOLUTION rather than in material

  • less solubility of solute in membrane

• Φ > 1: membrane surface concentration greater than solution

  • prefers to be in MEMBRANE rather than in material

• Φ =1: same surface concentration

Lesson 5: Modeling Drug Release

What are the different drug release mechanisms:

• Dissolution, diffusion, osmosis, partitioning, swelling, erosion

How do we determine which drug release mechanism occurred?

• given graph of time vs. cumulative release%

• look at r² and if it’s similar to the model

• Look at y = Ax + B —> K = 10^B —> n = A

• n is what drug release mechanism

• Fitting only valid up to 60% cumulative drug release

Types of Models:

1. Zero order

2. First Order

3. Hixson Crowell

4. Higuchi *

5. Korsmeyer Peppas **

If it looks like higuchi —> korsmeyer peppas —> determine release mechanism

Fick’s Laws: How fast something dissolves

1. First law: how fast diffuses across barrior: flux (flow of solute) is proportional to concentration gradient

2. Second Law: concentration changes over time bc of diffusion

   1. change in concentration with time in that region is proportional to change in concentration gradient at point in system

   2. basically saying it goes from high to low until it becomes even concentration gradient then it slows down

3. Fickian: no deformation/stress to matrix; nonfickian: structual changes

4. Nonfickian: polymer properties make it release (erosion) NOT mass diffusion/concentration gradient

Miscibility: does it completely dissolve into a homogeneous mixture

• important so drug releases uniformly + faster

• Flory HUggins: Is it miscible: x closer to 0 = more miscible the pair

  

Lesson 6: Drug Delivery from Polymers

Porous Media:

• can be regular array of lyndrical pores, foam, granular, fiber matrix

• specific surface and porosity (0.9 in interstitial, 0.06 brain 0.3 skin, 0.6 tumor)

Solute transport behavior based on porosity (how much is pores) and pore connectivity

• Nonpassing pore: one opening

• Passing pore: two opening goes through medium

• Isolated pore: just floating inside medium

Not all pores are accesible by solute (can be too small, connection is too small)

Size Exclusion Chromatograph: separates macromolecule by size through porous medium

Macromolecules can be flexible and can go through as a random coil

What influences pore permeability:

• Size

• Shape

• Flexibility

• Charge, charge-charge interactions in matrix

• pH

• Hydrophobicity/hydrophilicity

• Ionic Strength

• Dielectric Constant of Medium

Darcy’s Law: flow rate is directly proportional to the pressure gradient of medium and inversely proportional to the medium's resistance to flow

• v = -K∇p

  • K is hydraulic conductivity constant, resistance to flow

    • inversely proportional to viscosity

  • p is pressure

• 

Drug Eluting Polymers: norplant release hormone at constant rate (contraceptive)

Other release mechanisms: Triggered drug release, Hydrolysis, Polymer-drug interactions, Drug-drug interactions, Polymer relaxation, Pore closure, Heterogeneous degradation, Formation of cracks or deformation, Collapse of the polymer structure

Drug Release Profile:

• zero order release profile: straight line

• burst profile

  • moment it gets wet, drug comes out really quickly

  • NOT what you want unless you want fast acting

  • can put you over therapeutic window really quickly (bad), want sustained release so you can control it better

  • if you want to release burst release, don’t get it wet make it more hydrophobic

• triphasic release:

  • initial first release, zero order, plateau (over)

  • phase 1: first release (looks like higuchi)

  • phase 2: steady state diffusion (constant zero order)

  • phase 3: polymer erosion  (under)

    • hydrolyzes + pH change ==> degradation

    • bulk erosion: whole thing just bursts

    • surface erosion: outside dissolves, then only inside

• biphasic release

  • inital first release, zero order (no plateau)

Lesson 7: Water Soluble and Degradable Polymers

Structures of Polymers:

• Homopolymer: all monomer A

• Copolymer: made of two monomers A and B

• Polymer Blend: strands of only monomer A and strands only monomer B

Structure of Polymers:

• Size and Structure

• Polydispersity (nonuniformity)

• Solubility

  • larger = less soluble

  • branched = more soluble

• Stability (ph, temp, degrading)

• Density

• Crystallinity: strong IMF = high glass transition temp

  • reversible transition in amorphous materials from hard + glassy to viscous rubbery meaning it gets wiggly + elastic

• Strength

Biodegradable Polymers:

• Synthetic vs. natural

• degradation through ester hydrolysis (more hydrophilic = faster)

  • crystallinity and water content

• ester links (C=O-O)

What causes dehydration:

• polymer hydration, crystalline, bond lability (how easy broken)

PGA - semicrystalline + more water soluble/degradable

PLA is semicrystalline + more hydrophobic / stable

Copolymerization (combine) amorphous, inc in lactide/glycolide = inc crystallinity = slow drug release

If you change ratio, inc PLA degrades slower

If you add PEG blocks inc hydrophilicity of PLGA

Silicone (polysiloxanes)

• easily cross linked at room temp, very flexible + elastic

• Good as adhesive

If it looks wavy it’s a naturally derived water soluble polymer (ester)

Protein Polymers:

• Collagen (gelatin)

• Fibrin, elastin

• Proteoglycan (filler)

• Albumin (stability)

• Decellularized ECM

Lesson 8 Polymer Synthesis and Characterization

Process for making polymer: Select monomer + distill (remove oligomers), polymerization, purification (manipulate solubility to leave behind), blending, casting, post processing

Polymerization:

• step growth: add monomer or dimer or whatever fits (erosion profile), condensation (ester bond) and addition polymerization

• chain growth: adding monomer to one end (burst)

  • 1. Initiation, 2. propagation, 3. transfer, 4. termination

  • FRP (unpaired electrons) not very even, reversible deactivation has a step to slow it down to make it low polydispersity (RAFT)

• living chain growth: zero order

Polycondensation: molecule is eliminated, not necessarily water (polyester, polyamide)

Nylon: alcohalide bonds w/ hydrophilic, monomer A + B not miscible, film and step growth at surface

Polyaddition: no elimination, glue/epoxy (polyurethane)

Ionic Polymerization: cationic/anionic electrophiles start and only uses vinyl monomers

Ring opening polymerization: polyether, polyester, polyamide

Mixing monomers:

• block copolymer: AABB

  • link end groups, polymerize different monomer, end of first is macroinitiation for other reaction, end of first initiate next polymer chain

• random copolymer: ABAAAB

• alternate copolymer: ABAB

Polymer Characterization Methods

1. Size and Mw: Size Chromatography, Light scattering, mass spec

2. Chemistry: Nuclear magnetic spectroscopy, absorption spec (IR Raman)

3. Physical Properties: Mechanical (stress/strain), diff scanning calorimetry (glass temp), thermogravimetric analysis (mass over time as T inc for stability)

Lesson 10: Self Assembly

Surface free energy controls what happens at the biointerface

• NEED positive energy to create unit area of surface

• Equilibrium by minimizing surface energy —> curve

  • polar outside, nonpolar inside

• Maximize entropy

Condensation: if greater than opp of dissolving occurs

• u > 3/2 KT

• Self energy (u): strength of interaction of molecule and neighbor

Aggregates form if u0n (interaction free energy per molecule) decreases with number of molecules

At low concentrations —> favorable to exist as monomers

Increase concentration until Critical Micelle Concentration (CMC) —> form aggregrate

Hydrophobic tails want to decrease a (interfacial area, a), reduce water exposure

Hydrophilic heads want to increase a (interfacial area), spread apart

C = v / (a * l)

• C is critical packing parameter

• v is volume of hydrocarbon chain

• l is critical chain length

• a is optimal area for headgroup

• the bigger the C the more closely the heads wanna get together

Also control self assembly:

• Amphiphile concentration

• solvent system

• rate of addition

• temperature

• sonication

Higher Ordered Structures:

• first create spherical micelle —> self assemble into rod —> stack on each other to make a group (silica condenses on outside) —> calcinate which removes micelles (solvent) —> fully silica (porous sand, you can put A LOT of drugs)

PEG (PEO) = Hydrophilic shield that gives stability, solubility, and stealth

PPO = Hydrophobic

The PEG PPO PEG sandwich is a triblock polymer

What are some ways that they can make specific interactions besides polarity

• Host-Guest: specific size

  • host: cyclodextrine (ring of sugar) w/ hole in center

  • guest: hydrophobic (adamantane)

  • noncovalent bond so no catalyst required

  • How to get guest out: shear stresses

• Organometallic:

• Pi pi stacking: 2 aromatic groups noncovalent on top

• Hydrogen bonding: DNA

• Layer by Layer: coiled coils (alternating polymer peptide and silica templates can dissolve to get the capsules

  • Either lasagna or a ball

Lesson 11: Hydrogels

What is a hydrogel: network of cross linked polymer chains

• spaces that can absorb/trap a lot of water

• insoluble (swell and do not dissolve)

• soft and flexible

Gelation: process where solution of polymers floating around become crosslinked and fills in a 3d space making a gel

Chemical Hydrogels

• covalent bonds = generally permanent

Physical Hydrogels

• noncovalent bonds (weaker) = reversible

How to make a hydrogel:

• Inputs (solution phase)

• Generation: put liquid into polymer matrix

• Consumption: monomer consumed by substrate, agents consumed, chemical activation

• Output: gel phase

How to measure hydrogel:

• Chemical:

  • GPC/SEC

  • NMR

  • Plate Reader

• Physical:

  • Mechanical Tester

  • Scale

  • Rheometer

• Optical

  • Microscopy

  • Light Scattering

Increasing crosslinking = increase viscosity — stiffer = higher shear rate required for induced flow

More crosslinking = stiffer (high young’s modulus) = lower swelling

Fick’s Law: how fast drug can move THROUGH polymer network (hydrogel)

• Dependent on pore structure, cross-linking, interaction w/ solutes

Hydrogels not just for storing water but can encapsulate (trap)

• put drugs or actuators inside the pockets within a hydrogel

• hydrogel protects it or controls release

Lesson 12: Drug Carriers

Liposomes: vesicle where aqueous volume on inside enclosed by phospholipid bilayer

• from 20nm to several micrometers

• can be multilamellar: concentric number of phospholipid bilayers each separated by an aqueous phase (way bigger)

Parts of a Liposome:

• Coating

  • PEG (stealth cloak so it’s not destroyed immediately)

  • Targeting agent (bind to specific things so it releases at site)

• Phospholipid

• Cholesterol: stability

• Payload

  • Hydrophobic drugs in the bilayer

  • Hydrophilic drugs in the core

Phosphatidylcholine (naturally in cell membrane) amphipathic

• Hydrophilic heads

  • Phosphate group + choline group

  • Glycerol backbone

• hydrophobic tail

  • 2 fatty acid chains

  • kink (double bond) if unsaturated

  • 10-24 carbons, 0-6 double bonds in chain

Drug Release Mechanisms: how does it get inside a cell

• Endocytosis: carrier gets inside, whole thing eaten by endosome, lysosome degrade it and lets drug in **most common

• Fusion: carrier fuses w/ membrane, letting drug in

• Adorption: drug sticks to membrane and something else happens idk

• Lipid exchange: drug slips between gap during exchange

Doxil: lipsome that carries chemotherapy drugs for cancer (hydrophilic)

• when it dries it crystallizes as a rod

—

Lipid Nanoparticle (LNP)

• Encapsulates DNA/RNA

• It’s positively charged so the DNA stays on the inside

• No bilayer, lot of lipids packed together (condensed) and DNA is at center

4 Lipid LNP System:

1. Helper Lipid: for bulk

2. Ionizable Lipid: makes it positive

3. Cholesterol: stability stiffen

4. PEG: makes sure it doesn’t get blown up and not stay floating around for too long

How lipid nanoparticles get inside and delivers mRNA:

• put desired mRNA gene inside

• Gets into cell membrane through endocytosis

• Escapes endosome

• mRNA can go downstream to create ribosome which expresses whatever tf

Micelles: kind of like a lipsome except it doesn’t fold on itself with head then tail inside, liposome has a bilayer with head, tail, head, core

How to get the drug inside a micelle:

• chemical conjucation to polymer backbone

• physical entrapment: dialysis or emulsification

How to release the drug from the micelle:

• diffusion

• dissociation

  • pH

  • temperature

  • cleavage biomolecules

• unimer (strand) that cleaves (polymer drug bond) micelle

Gold nanoparticles:

• really fucking small (wavelength of light)

• inert and biocompatible

• drug on the surface: covalently bonded

• target specific if carrying ligands

Silica Nanoparticles:

• either solid or porous

• Drug or imaging agents inside pores

• **can have gold outside silica inside

Quantum Dots:

• made of cadmium (toxic)

• extremely small, fluorescent (easily visible)

• drugs, targeting ligands, polymers inside

Equations:

Thermodynamics:

Dissolution: how fast it dissolves (assume stationary layer of thickness h)

Will it dissolve:

How does it spread out over time?

Will condensation occur? (opposite of dissolve)

How to calculate Self Energy:

Permeability

Porosity:

Structures: