Direct evidence of gel–sol transition in cyclodextrin-based hydrogels as revealed by FTIR-ATR spectroscopy

Crupi, V.; Majolino, D.; Melone, Lucio; Punta, Carlo; Rossi, Barbara; Toraldo, Fabio; Trotta, Francesco; Venuti, Valentina

doi:10.1039/c3sm52354c

Cited by 31 publications

(69 citation statements)

References 41 publications

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“…the gel). 35 This description of swelling phenomena of nanosponges seems to be consistent with the experimental observation [36][37][38] that NS hydrogels undergo the change of their physical state, from a highly viscous gel to a liquid phase, by varying the hydration level or the temperature of the system. Recent HR-MAS NMR experiments 24 revealed that the regime of diffusivity of molecular species in NS hydrogels is modulated both by structural factors (i.e.…”

Section: 40supporting

confidence: 66%

“…Therefore, the formation of hydrogels by hydration of NS is supposed to occur after the progressive penetration of water molecules inside the hydrophilic pores present in the nanosponge structure. [35][36][37][38] Moreover, the presence in the polymeric structure of NS of a great number of carboxylic groups makes the water sorption steps dependent on the pH of the starting solution, leading to a change in the mesh size of the hydrogel network 2 and in a different swelling ability of the system. For example, by hydrating b-CDPMA14 with Na 2 CO 3 solution of increasing concentration (from 10 to 25% w/w), an enhancement of the swelling capability with respect to neutral H 2 O is clearly observed (see photographs in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…35,36,[39][40][41] The separate and complementary investigation of the molecular dynamics of the confined water and nanosponge polymer matrix [39][40][41] revealed that the engaged water molecules turned out to be more liquid-like and less strongly bound to the polymer's functional groups of NS. 40,41 Consequently, the gelation phenomena in NS hydrogels are thought to be driven not only by the formation of hydrogen-bond (HB) networks between water and the hydrophilic groups of polymers, but also by dispersion effects, such as the establishment of non-covalent interactions between the solvent and the more hydrophobic parts of the polymer skeleton.…”

Section: 40mentioning

confidence: 99%

“…n = cross-linking agent in molar excess with respect to CD) used in the synthesis of NS. [29][30][31][32][33][34] Moreover, strong experimental evidence has been found that the mechanism of water uptake and the gelling behaviour of NS are intimately connected with the structural arrangement of the polymer network [35][36][37][38] as well as with the balance between hydrophobic and hydrophilic moieties in the chain side groups of the polymer.…”

Section: Introductionmentioning

confidence: 99%

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Toward an understanding of the thermosensitive behaviour of pH-responsive hydrogels based on cyclodextrins

et al. 2015

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The molecular mechanism responsible for the thermosensitive behaviour exhibited by pH-responsive cyclodextrin-based hydrogels is explored here with the twofold aim of clarifying some basic aspects of H-bond interactions in hydrogel phases and contributing to a future engineering of cyclodextrin hydrogels for targeted delivery and release of bioactive agents. The degree of H-bond association of water molecules entrapped in the gel network and the extent of intermolecular interactions involving the hydrophobic/ hydrophilic moieties of the polymer matrix are probed by UV Raman and IR experiments, in order to address the question of how these different and complementary aspects combine to determine the pH-dependent thermal activation exhibited by these hydrogels. Complementary vibrational spectroscopies are conveniently employed in this study with the aim of safely disentangling the spectral response arising from the two main components of the hydrogel systems, i.e. the polymer matrix and water solvent. The experimental evidence suggests that the dominant effects in the mechanism of solvation of cyclodextrin-based hydrogels are due to the changes occurring, upon increasing of temperature, in the hydrophobicity character of specific chemical moieties of the polymer, as triggered by pH variations. The achievements of this work corroborate the potentiality of the UV Raman scattering technique, in combination with more conventional IR experiments, to provide a ''molecular view'' of complex macroscopic phenomena exhibited in hydrogel phases.

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Section: 40supporting

confidence: 66%

Section: Resultsmentioning

confidence: 99%

Section: 40mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Toward an understanding of the thermosensitive behaviour of pH-responsive hydrogels based on cyclodextrins

et al. 2015

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“…The study was performed on two types of NS, which were obtained by varying during the synthesis the molar ratio of cyclodextrin to the cross-linker. This choice was made on the basis of structural knowledge of the polymeric network of NS 14,15,30 and by considering previous results for the diffusivity of guest molecules inside NS gels. 31 Finally, the analysis of the thermal dependence of dynamical Raman parameters such as the dephasing time can be correlated with the mechanism of the release of Caf from NS hydrogels in response to external stimuli such as variations in temperature.…”

Section: 29mentioning

confidence: 99%

Guest–matrix interactions affect the solvation of cyclodextrin-based polymeric hydrogels: a UV Raman scattering study

et al. 2016

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The focus of the present work is to shed light on possible modifications of the molecular properties of polysaccharide hydrogels induced by the establishment of specific non-covalent interactions during the loading of a guest compound inside the gel phase. With this aim, a case study of the encapsulation of caffeine (Caf) inside cyclodextrin-based hydrogels, namely, cyclodextrin nanosponges (NS), is systematically investigated here by using UV Raman scattering experiments. The UV Raman spectra of the hydrogels, analysed as a function of temperature, concentration of the guest molecule loaded in the gel phase and pH, prove particularly informative both on the structural rearrangements of the hydrophobic/hydrophilic groups of the polymeric network and on the breaking/formation of specific guest-matrix interactions.Analysis of the temperature dependence of dynamical parameters, i.e., the dephasing time associated with specific vibrational modes of the polymer backbone, enables the proposal of a molecular picture in which the loading of Caf in NS hydrogels tends to favour access of the water solvent to the more hydrophobic portions of the polymer matrix, which is in turn reflected in a marked increase in the solvation of the whole system. The achievements of this work appear of interest with respect to the design of new possible strategies for controlling the diffusion/release of bioactive molecules inside hydrogel networks, besides corroborating the potential of UV Raman scattering experiments to give new molecular insights into complex phenomena affecting hydrogel phases. A IntroductionHydrogels are a class of soft materials that have attracted in recent years great interest from chemical and physical scientists. 1 Hydrogels are three-dimensional structures with the capability to retain large amounts of water while maintaining their elastic texture. 2,3 In the case of polymeric hydrogels, chemically or physically cross-linked networks of polymer chains create a characteristic three-dimensional matrix with interstitial spaces that are capable of hosting water. 4 The unique mechanical and physical properties of hydrogels, together with their biocompatibility and biodegradability, have made these materials attractive for a wide range of technological applications. For example, the physiochemical similarity of hydrogels to the native extracellular matrix suggested the use of these materials as scaffolds for tissue engineering and regenerative medicine. 5-7Indeed, synthetic matrices where cells can grow and interact with the environment in all three dimensions allow the in vivo behaviour of cells to be mimicked more efficiently than in previous methods based on the 2D growth of cells. Other examples include wound dressings, 8 super-adsorbent systems 9 and many suitable formulations for drug delivery. 10-12 Besides these practical aspects, hydrogels are interesting model systems for studying the role of hydrophobic and hydrophilic interactions in determining the gelling behaviour of biomacromolecules. This has been rece...

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Vibrational Spectroscopic Methods for Nanosponges

2019

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Direct evidence of gel–sol transition in cyclodextrin-based hydrogels as revealed by FTIR-ATR spectroscopy

Cited by 31 publications

References 41 publications

Toward an understanding of the thermosensitive behaviour of pH-responsive hydrogels based on cyclodextrins

Toward an understanding of the thermosensitive behaviour of pH-responsive hydrogels based on cyclodextrins

Guest–matrix interactions affect the solvation of cyclodextrin-based polymeric hydrogels: a UV Raman scattering study

Vibrational Spectroscopic Methods for Nanosponges

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