Magnetic Nanofluids for Chemical and Biological Processing

Andre Ditsch, Bernat Olle, Harpreet Singh,Lino Gonzalez, Marco Lattuada, Lev Bromberg,

Daniel I.C. Wang, Kenneth A. Smith & T. Alan Hatton

Department of Chemical EngineeringMassachusetts institute of Technology

Cambridge MA 02139

Magnetic Nanoparticles

Magnetic CoreSuperparamagneticApplications

Magnetic storage mediaMagnetic drug targetingProtein/Cells separationRNA/DNA purificationMagnetic resonance ImagingCatalystsMR FluidsMass and heat transfer enhancement

8 nm

15-20 nm

Polymer ShellColloidal stability

Functionality

Functionalised Magnetic Nanoparticles

Coating Material FunctionMagneticparticle Perfluorocarbons O2Transfer Enrichment

10 nm15-20 nm

Chiral Moieties Optical Resolutionof Racemic Mixtures

PhospholipidsLigands

Protein Purification

Block Copolymers Removal of OrganicContaminants

Non-volatile, colloidal solventsVery high interfacial areasLow surface activityReadily recovered by magnetic filtration

Protein Purification

Proteins increasingly used in place of small molecules in industry and medicine.

Proteins are much more specific and potent than small organic molecules.

Separations of proteins typically the major processing cost.Up to 80% of processing costs come from purification.

Therapeutics High purity High cost Low volumes

Industrial Enzymes Low purity Low cost Large volumes

Purif

icat

ion

Cos

ts(%

of t

otal

Pro

duct

ion

Cos

ts)

100

0

New methods needed for economical protein

production

Protein Adsorption Systems

High ∆PPore diffusion

limitations

Expanded BedShort Contact TimesLimited Flow Range

Can Handle CellsLow Capacity

Low flux

Stirred SystemControlled Contact Times

Fouling of Membranes

Packed BedPlugging

Low VelocitiesDispersionNo cells!

Colloidal Adsorbents

Stable dispersion of adsorbents as colloidal entities

High surface areas

106

107

108

0 10 20 30 40 50 60Are

a pe

r Vol

ume

, m2 /m

3

Colloid Diameter d, nm

0.010.02

0.050.10

A/V = 6φ/d φ, ColloidVolumeFraction

No diffusionalResistances

τ =r2/Dφ2/3 ~ 0.1- 10 ms~ 5 - 50 nm

colloidal entities

Process Overview

N S

Process Overview

N S

Process Overview

N S

Adsorptive Capacity?Particle Stability?Particle Capture?

Cells & Protein

Cells,Protein& MF

RecoveredCells Recovered

Protein

MF RecoveredMF

Cells & Protein

Cells,Protein& MF

RecoveredCells

RecoveredProtein

RecoveredMF

High Gradient Magnetic Separation (HGMS)

Stainlesssteel wire

(50µm)

Magnetic force on particle:

HMVF corecoreomag ∇= µ

Fmag

Fdiff

Fdrag

Clusters Needed for Effective Nanoparticle Capture by HGMS

Small particles - diffusion controlledaffected by bulk concentration

Large clusters - convection controlledno concentration effect18 nm

140 nm

Commercial HGMS Units

Polymer Synthesis

Common, readily available monomers – scalable process

High charge density at all relevant pH (SO3

-)

Variable hydrophobicity for additional specificity(Aromatic ring)

Strong attachment to Fe3O4(COO-)

Molecular weight from 2kDa to 300kDa with Na2S2O5

Particle Synthesis

Magnetic Nanoparticles

10 nm

Single crystal magnetic coreReversible recovery

Poly electrolyte coatingTunable adsorption

Easy flow around cellsNo diffusional limitationsColloidally stable

Purification of Drosomycin

Drosomycin least hydrophobic of bound proteins

Elution of nearly pure (90%) drosomycinwith pH=7, 0.5M NaCl

Complete elution of all proteins at pH=10, 0.5M NaCl

Allows re-use of particles

Comparison with other methods

(Capacity) x (speed) 30x better than best found in literature, 100x standardOnly 0.1% of particles lost with short (10.5) cm column

1 Voute et al. Bioseparations 8: 115-120, 19992 Ganetsos and Barker Preparative and Production Scale Chromatography Marcel Dekker 1993

Oxygen Transfer in Fermentation

Xmax= X0e µt

NA = Xmaxµ/YC/O ~ 425 mmole O2/L hr

= kLa(C* - CL)~ 105 mmole O2/L hr

(DO2/δ)Bubble

Size

Depends on Henry’s Law

Constant

Should not focus on bubble and hydrodynamics!Need to enhance effective Henry’s Law Constant

Mass Transfer Enhancement

2

3

4

5

0 10 20 30 40 50 60

ln (

C*-

Cbu

lk )

Time (min)

φ = 0.005φ = 0

φ = 0.01φ = 0.02

φ = 0.04

0

20

40

60

80

100

0 20 40 60 80 100 120

% O

xyge

n S

atur

atio

n

Time (min)

φ = 0.005φ = 0

φ = 0.01

φ = 0.02

φ = 0.04

DO Probe

N2-Purged suspension exposed

to air at time t=0

Mass Transfer Enhancement

0.8

1

1.2

1.4

1.6

1.8

0 0.01 0.02 0.03 0.04 0.05

Enh

ance

men

t

φ (particle fraction)

1

2

3

4

5

6

0 20 40 60 80 100

Enh

ance

men

t

Temperature (oC)

20 nm, oleic acid coated NP φ = 0.0025

80 nm, PPO-PEO coated NP φ = 0.0025

KLa MeasurementsSulfite Reaction Method

100

1000

10 100

k La (m

mol

/(atm

*L*h

r))

Superficial Velocity ,Vs (cm/min)

φ = 0.01

φ = 0.005

φ = 0.0025

φ = 0 (control)

100

1000

1 10 100

k La (m

mol

/(atm

L h

r))

Power Input per Unit Volume, PG/V

L (HP/1000L)

φ = 0.01

φ = 0.005

φ = 0.0025

φ = 0 (control)

Dtank = 22cm

HL =

14.

5cm

Di = 10cm

VTOTAL = 20L

VWORKING = 5.5L

air to mass spec

42232

2

21 SONaOSONa Cu⎯⎯ →⎯+

+

[SO32-] = 0.67M

[Cu2+] = 1x10-3 M

Catalytic Nanoparticles DesignMagnetite nanoparticles:

• Modified with moieties containing highly nucleophilic groups• Selectively attack electrophilic groups such as P-O bonds

found in toxic organophosphates• Contain charged group on the surface: colloidally stable in

water

Fe3O4

Stabilizing polymers

Oxime

α-nucleophile: a heteroatom with an unshared electron pair adjacent to the nucleophilic center

α-nucelophiles: oximates, phenolates, etc.

C=N-OHH

Nucleophiles Thus Far Tested

PAM: 2-pyridinealdoxime(common antidotal drug)

p(VPOx-AA): Copolymer of oximatedpoly(4-vinylpyridine) and polyacrylic acid(novel polymeric nucleophile)

N

CH3

HC N OH

CH2

HC C

H2

HC

N

COOH

CH2

C N OH

Decomposition of Organophosphates

O

P(H3C)2HCO

OCH(CH3)2

F

O

PH3C

OCH(CH3)2

F

DFPSarin

O

PH3C F

Soman

OCH(CH3)CH2(CH3)3

Diisopropyl fluorophosphate: model nerve gas

OP+ Nanoparticle gives water-soluble phosphoric acid + fluoride ionNanoparticles are recyclable by HGMS

Method of analysis: continuous detection of F-

Kinetics of Hydrolysis

0.0001

0.001

0.01

0.1

1

10

0.01 0.1 1 10

k obsx1

03 (s-1

)

Concentration (mg/mL)

PAM/M

PAM

p(VPOx-AA)/M

M p(VP-AA)/M

Spontaneous Hydrolysis

Rapid hydrolysis in presence of oximated species

Recycling

0.00

0.10

0.20

0.30

0 1000 2000 3000

-ln(1

-Ct/[D

FP] o)

Time (s)

PAM/M

p(VPOx-AA)/M

1

2

3

1

2

3

Particles can be recovered and recycled with no loss of catalytic effectiveness

Applications

Catalytic decomposition of organophosphates:Numerous OP pesticides and insecticides Warfare agents such as sarin, soman, and VX

Drainwaters, industrial runoffs and spillsProtective clothingFilters, membranes, gas masks

Brownian: rotation of particle in fluid

Neel: rotation of magnetic vector within particle

10-810-710-610-5

0.00010.001

0.010.1

1

6 8 10 12 14 16 18

Rel

axat

ion

Tim

e, s

Particle Size, �

Neel

Brownian

τ B =

3Vη0

KT

τ N =

1f0

exp KVkT

⎛⎝⎜

⎞⎠⎟

Relaxation Processes

Magnetic Response of Nanoparticles

λ =µ0 M 2V14kT

≈µ0 χ 2 H0

2V14kT

? 1

20 nm

+ Fe3+ + Fe3+

χshell ≈ 1.3χdist

Magnetite NanoparticlePreparations

Aqueous RouteNucleation of magnetite nanocrystals from a solution of FeCl3 & FeCl2, NH4OH, 80°C. Various stabilizersPros: Cheap, fast, variety of stabilizersCons: broad nanoparticledistribution, irregular shape, average crystallite size fixed

Organic RouteIron-triacetylacetonate reduction by 1-2 hexadecanediol, at 300°C in benzylether,oleic acid+oleyl aminePros: narrow crystallites distribution, regular (controlled) shape, tunable sizeCons: expensive, works only with some organic stabilizers, chemistry poorly understood

20 nm

+ Fe3+ + Fe3+

Magnetophoretic Separation of Nanoparticles in Microfluidic Systems

Decreasing H

Fmag + Fdrag = −µ0Vp M f ∇H − 6πηRU p = 0

Fmag = µ0Vp ( M p − M f )∇H

= −µ0Vp M f ∇H

Fdrag = −6πηRU p

U p = −

µ0Vp M f ∇H6πηR

Magnetic Fluid

Flow Magnetophoresis for Nanoparticle Separations

Nanoparticle Separation and Focusing

Particle Resolution is affected byConvective dispersion (non-uniform velocity profiles)Non-uniform lateral field distributions

Magnetic Shells

Use layer-by-layer technique to coat polystyrene beads with polyelectrolytes and then adsorb magnetic nanoparticles.

Polymer core can be dissolved out using solvent.

Applications of Magnetic Chains and Rods

Fundamental studies on behavior under fixed and rotating magnetic field

Magneto-rheological effectsMagnetic actuators and valves Micromixers, pumps, etc. under a rotating magnetic fieldMagnetic nanowires (Bibette &Vivoy) Magnetic pillars can be used for separations (currently used in

separation of DNA (Doyle's research))Functionalized chains can be used for separations

Molecular movement of a molecule through the maze of chains onlygoverned by size and interactions with chains...

Separation of paramagnetic species

Bead Alignment and Coupling

Beads can be aligned in microchannel under magnetic field and joined together either using sol-gel chemistry or

chemical coupling with appropriate linker.

Rigid Magnetic Chains

Sol Gel kinetics (Titanium isopropoxide as precursor)

Extremely fast hydrolysis reactionLinking requires preferential nucleation on the bead surface

Magnetite beads coated with PDAMAC and resuspended in anhydrous ethanol; Kpw = 60

Water of hydration in the PDAMAC shell ensures reaction on the bead surface onlyPositively charged bead captures negatively charged nucleated titania efficiently

Tethered Flexible Magnetic Chains

25 µm

50 m No

(c) (d)

50 m

50 m

(a) (b)

50 mNo

25