Saratov Fall Meeting 2014 Optical Rotatory Dispersion and Circular Dichroism Films Based on Chitosan in the Form of Polysalt and Polybases Olga N. Malinkina* 1,2, Anna B. Shipovskaya 1,2, Olga F. Kazmicheva Institute of Chemistry, Saratov State University 2 - Research and Education Institution of Nanostructures and Biosystems, Saratov State University

Abstract Optical activity of films based on chitosan in different chemical forms by spectropolarimetric methods were investigated. These film samples are used as sorption material, and as substrates for cell culturing tissue-engineering and scaffold constructions. It was found that the spectra of optical rotation and circular dichroism spectra of the films of chitosan in the form of polysalts and and polybase significantly different in magnitude of the optical rotation values of plane-polarized and circularly polarized light.

Application of Chitosan-based Substrates for Biophotonics Properties of chitosan: Biospecificity Optical activity Biocompatibility The ability to form polyelectrolyte complexes Antioxidant properties Stability control of dispersions of metallic nanoparticles Based on the foregoing advantages, the application chitosan-based platform makes it possible to obtain spatially localized biofunctional surfaces for planar optical waveguides can preconcentrated analyte in the zone of the sensor from a large volume of solvent, followed by the implementation of various optical layouts detection (SPR, SERS, fluorimeterically, absorption, scattering, and so on.) Advantages of platforms based on chitosan for planar optical waveguides:  Biomimetic structure  Biofunctionalization of a surface  Easy to assemble  Low cost  High sensitivity

SEM images of the thin film surface from aqueous acetic solution of chitosan In the form of polysalts (S-form) Molecular weight of chitosan 550 kDa (CS-550) 700 kDa (CS-700) In the form of polybases (B-form) alkaline treatment for 1 hour alkaline treatment for 1 hour The surface morphology of the thin films was evaluated by SEM on a MIRA/LMU scanning microscope (Tescan, Czech Republic) at a voltage of 8 kV and a conductive current of 60 pA. A 5-nm gold layer was sprayed onto all samples with a K450X carbon coater (Germany; spraying current, 20 mA; spraying duration, 1 min).

AFM images of the morphological structure of the thin film surface from aqueous acetic solution of CS-550 2D 3D Alkaline treatment for 1 hour AFM images of films on a microscope glass slide were recorded with an Integra Spectra microscope (NT-MDT, Russian Federation) in tapping mode. For image acquisition NSG11 probes (NT-MDT) with resonance frequency in the range of 320 kHz, force constant 3–38 N·m −1 and tip curvature 10 nm and cantilevers for contact and non-contact mode microscopy semicontact were used. AFM images of the surface of the films were processed in the program Gwyddion alignment of the background and with the use of smoothing of three pixel length median filter to eliminate single-pixel noise emissions. S-formB-form

ORD spectra of the thin film from aqueous acetic solution of CS CS-550 CS-700 S-form B-form S-form B-form Optical rotator dispersion (ORD) of the thin films was measured using a thermostatically controller spectropolarimeter (SPU-E, Russian Federation) at wavelengths of 280, 365, 436 and 691 nm.

Lowry (1/[  ]  2 ) Lowry (1/[  ]  2 ) Yang-Doty ([  ] 2  [  ] ) Yang-Doty ([  ] 2  [  ] ) Geller (1/[  ] 2  1/ 2 ) Geller (1/[  ] 2  1/ 2 ) Sample of chitosan Chemical form Rotational constant, |K|  Dispersion constant 0, nm Lowry Yang- Doty Geller Average Lowry Yang- Doty Geller Average CS-550 S-form CS CS-550 B-form CS Drude equation (nm)  wavelength optically active electronic transition, К – rotational constant, 0 (nm)  dispersion constant (nm)  wavelength optically active electronic transition, К – rotational constant, 0 (nm)  dispersion constant To determine the constants K and λ 0 was used graphical transformations

CD spectra of the film from aqueous solution of chitosan CD spectra were recorded on an automated spectrometer circular dichroism Сhirascan CD Spectrometr (France) at 20 °C in a nitrogen stream with a scan range of nm, the sensitivity range 1· The specially designed for the measurement of the CD quartz cuvettes of 2 mm pathlength was used. The spectra were recorded with a scan speed of 0.1 nm/s and averaged over five scans. All the CD spectra were buffer-subtracted and smoothened using Pro-Data software provided with the Chirascan CD spectrometer CS-550 CS-700 Curve 1 - S-form Curve 2 - B-form —NH 3 + An - —NH 2 —NH 3 + An -

Optical properties and surface characteristics of thin film from aqueous acetic solution of CS-550 & CS-700 Sample of chitosan Chemical form AFM morphological structure of the thin film surface ORDCD |[α] | |K|  [θ] 25 λ0 0 CS-550 S-form Grain structure with a “grain” size from 4 up to 6 nm CS-700 Grain structure with a “grain” size from 10 up to 19 nm CS-550 B-form Grain structure with a “grain” size from 8 up to 14 nm CS-700 Grain structure with a “grain” size from 15 up to 29 nm

Conclusions Surface and optical properties of thin films of CS-550 and CS-700 in S- and B-forms were studied by methods of SEM, AFM, ORD and CD. The essential differences in the surface topography at the submicron level, the values ​​ of specific optical rotation and ellipticity of the films of different chemical form were found. When the chemical modification of S-form in the B-form increases the size of "grains" of the supramolecular structure, which is probably due to the change in the conformation of the macromolecular coil as a result of the removal of the counterions from amino groups. Absolute values ​​ of specific optical rotation of the films of chitosan in B- form exceeds | [α] T λ | of the S-form. The CD spectrum revealed of the differences in the wavelength of n → π * transition of optically active chromophores in the protonated and unprotonated forms. The influence of molecular weight on the optical activity ([α], [θ]) chitosan was found.