1. Synthesis and characterization of magnetite nanoparticles on DNA wrapped single-walled carbon nanotubes
Gordana Ostojic, Mark C. Hersam
Materials Science and Engineering
Northwestern University
February 16, 2019

2. Carbon nanotubes l d
Diameter (d) depends on n,m (distribution around 1 nm)
Length (l) depends on type of growth and processing (distribution up to microns)
* Hersam group developed a method for diameter and electronic type purification
* The length purification can be achieved by Size Exclusion Chromatography (SEC)
- Huang et al, Anal. Chem. 77,6225 (2005)
Peak position and broadening (and intensity)
depend on dielectric properties of the surroundings
Metal SWNTs are Luttinger liquids (spin and charge travel with different velocities).

3. Carbon nanotubes in bio/medicine
SWNT noncovalently functionalized with aminoacids, proteins, nucleic acids, PEG,
chitosan, fluorofores etc.
Proposed bio/medical applications: Sensing, NIR induced hyperthermia, Transporters,
NIR fluorofores
Toxicity: dependent on catalyst, surfactant, size and administration
Rabbit intravenous administration of Pluronic F108 solubilized SWNT,
Displacement of surfactant with blood proteins, half-life of 1 h and liver accumulation.
Cherukuri et al., PNAS, 103, 18882, (2006)
N. W. S. Kam et al., PNAS. 102, (2005).

4. Magnetite growth on SWNT/DNA
Procedure:
Encapsulate SWNTs with ssDNA. Used (GT)10 which is known to pair to itself.
- Harsh (sonication/centrifugation) or mild (surfactant replacement dialysis) method
Dialyze away the excess DNA and NaCl remained after encapsulation.
- Verify with HPLC
Degas SWNT (or control DI water) solution.
Add particular amount of iron chlorides = aqueous solution of 0.03 M FeCl2 and 0.06 M FeCl3.
Add ammonium hydroxide solution, amount according to stoichiometric equation.
Dialysis of excess salts produced.
Steps 4 and 5 are done inside glove bag filled with nitrogen.
XRD
Sample
SWNTs [%]
Iron Chlorides [ml]
Diameter
[nm] A 50 60 - B
120
6.73 C
300
9.46 D
600
9.77 E 10
11.42 Ct
8.00 Dt
9.45

5. Optical Absorbance Characterization
* Crucial: retained desirable NIR optical peaks of SWNTs (noncovalent binding)
Fe3O4 spectra featureless,
adds to the background
SWNT peaks retained
without clear broadening
for ALL samples probed →
No carrier transfer
between nanotubes

6. Relaxation measurements
T1 (90-tau-90)
T2 (Echo Decay)
1 ml of SWNT concentration-adjusted
samples sent to:
Process NMR Associates, LLC Danbury, CT
for low-field relaxation measurements
Results:
1. SWNT and 0.3 mM magnetite behave
the same: several time decays due
possibly to DNA and aggregates
mM magnetite behaves as expected
decay ~3 ms compared to 72 ms of water

7. Other possibilities
SWNT/DNA functionalization with other metals: Pt, Ag, DNA intercalators like cisplatin
2. SWNT/DNA functionalization with two different biomolecules (DNA and protein).
Peak position shifts with the different DNA and protein amount on SWNT. Protein content also confirmed by SEC.
3. Controlled release of DNA intercalators (cancer drugs).
XRD of Pt grown on SWNT/DNA
Protein and DNA co-functionalization of SWNT

8. Proposed experiments The 1D dimensionality correlation probing:
Repeat relaxation measurements for several magnetite densities vs same magnetite densities in DNA solution.
2. If it is a 1D correlation prepare SWNT of different lengths
3. Test citrate for more uniform particle formation
4. Test making of Gd2O3 and just Gd
5. Develop joint procedure for both Gd and Fe3O4