TEMPO-oxidized cellulose nanofibrils as a functional component in ultra-low solid double network hydrogels for biomedicine

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School of Chemical Engineering | Master's thesis

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Date

2025-09-26

Department

Major/Subject

Biotechnology

Mcode

Degree programme

Master's Programme in Chemical, Biochemical and Materials Engineering
Kemian-, bio- ja materiaalitekniikan maisteriohjelma
Magisterprogrammet i kemi-, bio- och materialteknik

Language

en

Pages

77

Series

Abstract

This thesis explores the potential of TEMPO-oxidized cellulose nanofibrils (TCNF) as a component in the ultra-low solid double network (DN) hydrogels for biomedical use. The main goal was to determine the gelling point (GP) of TCNF and how sonication and surface charge influence the rheological behaviour and structure of TCNF, using rheological analysis, Atomic Force Microscopy (AFM), and light microscopy. TCNF with low (705 mmol/kg), medium (1011 mmol/kg), and high (1205 mmol/kg) charge densities were studied. The results showed that both the charge, and sonication affect the GPs of TCNF. Low charge TCNF had lower GP due to fibrillar aggregation, while the high and medium charge TCNF showed higher GP due to electrostatic repulsion between more extensively carboxylated fibrils. Sonication affected the GPs of more carboxylated TCNF of high and medium charge, while the GP of the low charge TCNF was affected the least due to lower concentration of carboxylic groups. AFM scans of spin-coated TCNF showed dense fibrillar network with individual fibrils and flocks on all samples, regardless of sonication or charge difference. The light microscopy images revealed the same pattern, with flocks and individual fibers on all spin-coated TCNF. The TCNF hydrogels did not display expected sol-gel transition in rheological tests, instead, they stayed in the critical gel (CG) state. Additionally, the TCNF samples exhibited a self-similar structure with repeating fibril flocks and individual fibers across multiple scales (AFM, light microscopy, and the naked eye). Thesis also explored the enzymatic digestibility of hemicellulosic components using endoglucanase enzymes from VTT. One of the tested endoglucanases showed high specific activity towards both substrates. The thesis confirms the formation of hydrogels at ultra-low solid concentrations of TCNF, which facilitates the further assisted degradation and tunable structure for controlled drug delivery systems. The prolonged CG state behaviour and self-similar structure of TCNF was not reported in previous studies, hence, opens a new research direction on application of nanocellulose in biomedicine.

Description

Supervisor

Kostiainen, Mauri

Thesis advisor

Arola, Suvi

Keywords

TEMPO-CNF, sonication, surface charge, double-network hydrogels, mixed linkage glucan, critical gel, self-similar structure

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https://urn.fi/URN:NBN:fi:aalto-202512179365

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[dipl] Kemian tekniikan korkeakoulu / CHEM