Adhesive Layer-by-layer Films of Carboxymethylated. Cellulose Nanofibril-dopamine Covalent Bioconjugates

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1 Adhesive Layer-by-layer Films of Carboxymethylated Cellulose Nanofibril-dopamine Covalent Bioconjugates Inspired by Marine Mussel Threads Erdem Karabulut 1, Torbjörn Pettersson 1, Mikael Ankerfors 2 and Lars Wågberg 1,3* 1 Fibre and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, SE Stockholm, Sweden, 2 Material Processes, Innventia AB, Box 5604, Stockholm, Sweden, 3 Wallenberg Wood Science Centre, Teknikringen 56, 10044, Stockholm, Sweden *Corresponding author wagberg@kth.se Tel:

2 Figure S1. (a) A transparentt and self-supporting solvent-cast t film of unmodified cellulose nanofibrils (CNFC). The film was prepared by solvent-casting of a 1.4 g L -1 dispersion of CNFC in water at room temperature. The thickness is approximately 10 μm. This film can easily be peeled off from the polystyrenee petri dish and other types t of hydrophobic surfaces. s (b) A thin solvent-cast film (from( 1.4 g L -1 of CNFC-DOPA water dispersion containing 1 mm of FeCl 3 ) of the DOPA-modified cellulose nanofibrils (CNFC-DO( OPA) on a piece of polystyrene surface. The adhesive properties of coatings prepared by the DOPA modified nanofibrils differ significantly from thosee of their unmodified forms. (c) The stability in water of a freely-standing film prepared from pure CNFCC and an iron-inducedd coating off CNFC- DOPA on a piece of polystyrene surface.

Figure S2. The change in oscillation frequency and energy dissipation for the multilayer film of CNFC-DOPA and PEI-CAT.

of CNFC-DOPA and PEI-CAT was monitored by QCM-D.

layer of pure PEI, whichh confirms that the conversion of carboxyl groups on the nanofibril surface was not n 100% and that

On the t other hand, the steady deposition of PEI-CAT and CNFCbetween DOPA on this first layer pair was interrupted due to the

This can be attributed both to excessive modification of the primary amines of PEI interacting with the previous layer and to t

Therefore, bothh CNFC-DOPA and PEI-CAT were desorbed from the surface during the rinsing steps s (there e was no significant

3 Figure S2. The change in oscillation frequency and energy dissipation for the multilayer film of CNFC-DOPA and PEI-CAT. In order to gain a better understandingg of the DOPA functionalization on the formation of LbL film, the consecutive deposition of CNFC-DOPA and PEI-CAT was monitored by QCM-D. The decrease in oscillation frequency in Figure S2 shows thatt it was possible to adsorb an NFC-DOPA layer on a pre-cursor layer of pure PEI, whichh confirms that the conversion of carboxyl groups on the nanofibril surface was not n 100% and that there is an electrostatic interaction between the free carboxyl groups of o the CNFC-DOPA and the primary amines of PEI. On the t other hand, the steady deposition of PEI-CAT and CNFCbetween DOPA on this first layer pair was interrupted due to the weak electrostatic interaction PEI-CAT and CNFC-DOPA. This can be attributed both to excessive modification of the primary amines of PEI interacting with the previous layer and to t the stericc hindrance between the DOPA molecules which reduces the charge interaction. Therefore, bothh CNFC-DOPA and PEI-CAT were desorbed from the surface during the rinsing steps s (there e was no significant change in frequency and energy dissipation). When PEI-CAT was w replacedd with PEI, the LbL film build-up continued from the step where it was previouslyy interruptedd before and it was again possible to adsorb CNFC-DOPA A and PEI. It can be concluded that the degree of DOPA/CAT functionalization affects the multilayer film formation remarkably.

4 Figure S3. The AFM images and thickness profiles of (PEI/CNFC-DOPA) 8 film in (1a, 1 b) air, (2a, 2b) Milli-Q water and (3a, 3b) 1 mm of FeCl 3 solution.

5 b a Figure S4. The chemical structures of (a) 3,4-Dihydroxycinnamic acid (CAT) branched PEI-CAT conjugate.. and (b) Figure S5. The chemical mechanism of amide bond formationn between carboxylic groups of CNFC and primary amines of DOPA. (R:: -C 2 H 4 -C 6 H 3 (OH) 2 )

6 The covalent conjugation of CNFC and DOPA was performed using a zero-length crosslinker, water-soluble carbodiimide (EDC) in PBS buffer. The detailed information on carbodiimide cross-linkers can be found elsewhere.1-5 The mechanism of reaction is shown in Figure S4. The by-products were removed by a dialysis step, as confirmed by the FTIR and UV-Vis spectra of the conjugates. 10 F/R (mn/m) FeCl 3 H 2 O Apparent Separation (nm) Figure S6. Normalized force curves recorded between (PEI/CNFC) 7.5 film and silica particle upon withdrawal in Milli-Q water and 1 mm of FeCl 3 solution. The DOPA attachment degree was evaluated by recording the UV-Vis spectra CNFC- DOPA conjugates prepared decreasing amount of DOPA. As shown in Fig. S7, the intensity of maximum absorbance (A max ) decreases with the decreasing DOPA attachment. The conversion degree of free carboxyl groups to their DOPA forms was calculated by comparing the A max value at 281 nm of CNFC-DOPA conjugate in which the initial DOPA amount was higher than the total charge of CNFC. The attachment degree of DOPA was calculated as 30.0 %, 12.4 % and 10.2 % for the conjugates in which added DOPA amount was 0.03 mmol, 0.02 mmol and 0.01 mmol. Table S1 shows the A max values of 100 mg L -1 CNFC-DOPA conjugate dispersions corresponding to different amounts of initial DOPA.

7 Initial DOPA amount in the reaction A max at 281 nm mixture (mmol) Table S1. Amax values of the CNFC-DOPA conjugate dispersions prepared with different initial amount of DOPA. 0,25 0, mmol 0.02 mmol 0.06 mmol 0.03 mmol Absorbance 0,15 0, nm 281 nm 0,05 0, Wavelength (nm) Figure S7. UV-Vis spectra of the CNFC-DOPA conjugates prepared by adding different amounts of DOPA to the reaction mixture.

Figure S8. The build-up of a (PEI/CNFC-DOPA) 4 multilayer film f in the QCM-D at ph=3.5.

the change in energy dissipation respectively.

performing the QCM-D experiments at ph=3.5 (similar ph of FeCl 3 solution).

) Figure S8 shows the change in oscillation frequency of the QCM crystal and the energy dissipation.

Milli-Q water), but the dissipation change is much lower at ph=3.

It should be b noted that the AFM force measurements were performed by injecting the solutions to

8 Figure S8. The build-up of a (PEI/CNFC-DOPA) 4 multilayer film f in the QCM-D at ph=3.5. Left and right y-axes show the change inn normalized frequencyy (considering the 3 rd overtone) and the change in energy dissipation respectively. The influence of ph on the swelling of multilayer films of CNFC-DOPC PA was investigated by performing the QCM-D experiments at ph=3.5 (similar ph of FeCl 3 solution). (The ph of PEI, CNFC-DOPA and rinsing solution was ph=3.5.) Figure S8 shows the change in oscillation frequency of the QCM crystal and the energy dissipation. Itt is shown that the adsorbed amount of PEI and CNFC-DOPA did not differ to that at higher ph (in Milli-Q water), but the dissipation change is much lower at ph=3.5 which indicates that the PEI and CNFC-layers are slightly more rigid att low ph. It should be b noted that the AFM force measurements were performed by injecting the solutions to completely dry multilayer films which might lead to a sudden swelling in a short time period which reachess a saturation after a minutes of the injection. The QCM measurements weree performedd under completely wet conditions in which the swelling is inn equilibrium during the experiment.

9 REFERENCES 1. Yamada, H.; Imoto, T.; Fujita, K.; Okazaki, K.; Motomura, M. Selective Modification of Aspartic Acid-101 in Lysozyme by Carbodiimide Reaction. Biochemistry 1981, 20, Chase, J. W.; Merrill, B. M.; Williams, K. R. F-Sex Factor Encodes a Single-Stranded- DNA Binding-Protein (Ssb) with Extensive Sequence Homology to Escherichia-Coli Ssb. Proc. Natl. Acad. Sci.USA-Biol. 1983, 80, Chu, F. S.; Chang, F. C. C.; Hinsdill, R. D. Production of Antibody against Ochratoxin-A. Appl. Environ. Microbiol. 1976, 31, Chu, F. S.; Lau, H. P.; Fan, T. S.; Zhang, G. S. Ethylenediamine Modified Bovine Serum- Albumin as Protein Carrier in the Production of Antibody against Myco-Toxins. J. Immunol. Methods 1982, 55, Chu, F. S.; Ueno, I. Production of Antibody against Aflatoxin-B1. Appl. Environ. Microbiol. 1977, 33,

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