Scholar: Charmane ThurmandMentor: Dr. Minghui Chai

Department of ChemistryCentral Michigan University

PAMAM DendrimersDendrimers --- polymersPoly(amidoamine)--- PAMAM H2N

NH

NH2

HN

N

NH

N

NH2

HN

NH2

NH

NHN

NH

N

H2N

NH

NH2

HN

N

NH

N

NH2

NH

NH2

NH

NNH

NH

NH2

HN

H2N

NH

N

HN

N

H2N

NH

H2N

HN

N NH

HN

NH2

HN

H2N

NH

N

HN

NH2N

HN

H2N

HN

NNH

HN

N

O O

OO

O

O

O

O O

O

O

O

OO

O

O

O

O

O OO

O

O

O

O

O

OO

G0

G1

G2

G2 PAMAM Dendrimer

Core

Exterior

InteriorDendrimer

cascadesymmetricalspherical

dendritic-voidsmulti-functionalitymonodispersity

Based on the dendrimer’s multifunctionality, dendrimers can form complex with metal ions.

In this project: G2-PAMAM + Ag(I) ions complex

(nanocomposite)

In literature, an interesting finding was reported.

Potential applications: antimicrobial filter for water purification

antifouling coating for shipsRef: Balogh, L.; Swanson, D. R.; Tomalia, D. A.; Hagnauer, G. L.; McManus, A. T. Nano Letters 2001, 1(1), 18-21.

In order to understand the properties of the complexes for applications, the following questions need to be answered:(1) How stable are the Ag(I)-PAMAM complexes in aqueous solutions?

(the filter or coating has to be stable in water)

(2) Where do Ag(I) ions bind with PAMAM dendrimers (binding sites): exterior (i.e. surface), interior (may including core), or both parts?

(important to know this information to understand the antimicrobial property of the complex for applications)

NMR SpectroscopyNMR --- nuclear magnetic resonance

spin --- nucleus of the atoms in the chemical materials for the NMR test

Spectroscopy --- correlates the molecular structure with the energy (ΔE ) absorbed or emitted by the chemical materials

NMR spectrum --- the data collected from the NMR test (shown on the right)

ppm 3.5 3.7 3.9 4.1 4.3 4.5 4.7

ppm 50 60 70 80 90 110 130 150 170

H5

H4

H3

H2

O

NHO

O

N OH

O

NHO

O

N OH

NNN

N

NN N

N

COOH

COOH

COOH

COOH

HOOC

HOOC

HOOC

HOOC

1

2 3

4

56

78

8'

C8/C8’

C7 C6

C1

C5 C4

C3 C2

Investigation on the Stability of the Ag(I)-G2-PAMAM Complexes Method: 1H 1D NMR is used to monitor the Ag(I)-PAMAM

complex sample in water for several months.Rationale: If unstable, there will be changes in 1H NMR signals in the spectra; otherwise, no change will be observed.

Investigation on Binding Sites of G2-PAMAM Dendrimers with Ag(I) Ions

Method: 2D NMR 1H- 1H (homonuclear) COSY technique will be used to probe Ag(I)-G2-PAMAM complex

system in comparison with PAMAM alone system.Rationale: Where Ag(I) ions bind with PAMAM, there will be

changes observed in 1H signals. In comparison to 1D NMR, 2D NMR can provide three-bond 1H-1H proton connections in the PAMAM dendrimer structure.

Stack Plot of 1H NMR Spectra of the 12-run G2-PAMAM and Ag (I) ion complex sample over a period of 102 days

ppm2.32.52.72.93.13.33.5

12

12

12

12

12

4,8

4,8

4,8

4,8

4,813

13

13

13

13

2,6,10

2,6,10

2,6,10

2,6,10

2,6,10

5,9

5,9

5,9

5,9

5,93,7,11

3,7,11

3,7,11

3,7,11

3,7,11

1 Day

3.5 Days

6.5 Days

41 Days

102 Days

*

*

*

*

*

*Solvent Peak

2D COSY NMR spectrum of 1:16 G2-PAMAM-Ag(I) ion complex with a partial structure of G2-PAMAM dendrimer labeled in color numbers

F1 (ppm)

2.5 2.8 3.1 3.4

F2 (ppm)

2.6

2.8

3.0

3.2

3.4

12 13

4 8

4 8

12

13

3,7,11

5,9

5,9

3,7,11

2,6,10

2,6,10

N

N

NHO

N

NHO

N

NHO

H2N

HN

O

NH2

NH

ON

NHO

NH2

HN

O NH2

1

23

45

6

7

8

9

1011

12

13

1D 1H NMR stack plot with peaks labeled in color numbers for G2-PAMAM and Ag(I) ion complexes at different ratios.

N

N

NHO

N

NHO

N

NHO

H2N

HN

O

NH2

NH

ON

NHO

NH2

HN

O NH2

1

23

45

6

7

8

9

1011

12

13

ppm2.32.52.72.93.13.33.5

4,8

4,8

4,8

12,4,8

4,8

4,8

12

12

12

12

12

5,9

5,9

5,9

5,9

5,9

5,9

3,7,11

3,7,11

3,7,11

3,7,11

3,7

3,7

11

11

2,6,10

2,6,10

2,6,10

2,6,10

2,6,10

2,6,10

13

13

13

13

13

1:0 Ratio

1:4 Ratio

1:8 Ratio

1:12 Ratio

1:16 Ratio

1:20 Ratio

13

1D 1H NMR study shows that the Ag(I) ion complex of G2-PAMAM is stable in water .

The results from the NMR studies clearly show that the Ag(I) ions bind to the primary amino groups on the outermost layer of the dendrimer first then proceed to the interior and the core.

2D COSY NMR experiment can provide adequate resolution for the proton NMR signal assignments of the G2-PAMAM entity in the complex.

With these findings, the antimicrobial properties of Ag(I) ion complexes of PAMAM dendrimers can be understood and explained

CMU Chemistry Department for hosting the projectMMI for supplying the materials used in the project

Dr. Minghui Chai (research project mentor)Dr. Abhijit Sarkar (collaborator, MMI)Ms. Tracy Z. Zhang (collaborator, MMI)

Questions?