Post-synthesis modification of hydrogels. Total and partial rupture of crosslinks: Formation of aldehyde groups and re-crosslinking of cleaved hydrogels
“…Also, a minimum concentration of 0.5 % w/v was needed in order to obtain a crosslinked viscoelastic material. This behavior is commonly observed in polymeric viscoelastic materials and has been reported by several authors 45 , 46 . Figure 4 Elastic modulus for the synthesized poly(HEMA) B.…”
Organoboron compounds have been playing an increasingly important role in analytical chemistry, material science, health applications, and particularly as functional polymers like boron carriers for cancer therapy. There are two main applications of boron isotopes in radiation cancer therapy, Boron Neutron Capture Therapy and Proton Boron Fusion Therapy. In this study, a novel and original material consisting of a three-dimensional polymer network crosslinked with $$^{10}$$
10
B enriched boric acid molecules is proposed and synthesized. The effects of the exposition to thermal neutrons were studied analyzing changes in the mechanical properties of the proposed material. Dedicated Monte Carlo simulations, based on MCNP and FLUKA main codes, were performed to characterize interactions of the proposed material with neutrons, photons, and charged particles typically present in mixed fields in nuclear reactor irradiations. Experimental results and Monte Carlo simulations were in agreement, thus justifying further studies of this promising material.
“…Also, a minimum concentration of 0.5 % w/v was needed in order to obtain a crosslinked viscoelastic material. This behavior is commonly observed in polymeric viscoelastic materials and has been reported by several authors 45 , 46 . Figure 4 Elastic modulus for the synthesized poly(HEMA) B.…”
Organoboron compounds have been playing an increasingly important role in analytical chemistry, material science, health applications, and particularly as functional polymers like boron carriers for cancer therapy. There are two main applications of boron isotopes in radiation cancer therapy, Boron Neutron Capture Therapy and Proton Boron Fusion Therapy. In this study, a novel and original material consisting of a three-dimensional polymer network crosslinked with $$^{10}$$
10
B enriched boric acid molecules is proposed and synthesized. The effects of the exposition to thermal neutrons were studied analyzing changes in the mechanical properties of the proposed material. Dedicated Monte Carlo simulations, based on MCNP and FLUKA main codes, were performed to characterize interactions of the proposed material with neutrons, photons, and charged particles typically present in mixed fields in nuclear reactor irradiations. Experimental results and Monte Carlo simulations were in agreement, thus justifying further studies of this promising material.
“…We have previously reported the synthesis of AM-BIS-DAT HGs where the periodate mediated cleavage of DAT-crosslinks caused the formation of aldehyde FGs in the network. 24 In this work, we aimed to enhance their smart properties by incorporating an imine based self-healing behavior which could be triggered by periodate. Thus, AEMA incorporation was needed for obtaining amines in the network that would later be combined with the aldehyde FGs that could be formed by the presence of periodate.…”
Section: Resultsmentioning
confidence: 99%
“…As a straight forward protocol, we have previously demonstrated the use of an effortless post-synthesis modification of the cross-linker N,N'-diallyltartardiamide (DAT) to obtain valuable α-oxoaldehyde FGs. 24 This modification is promoted by the periodate-mediated cleavage of diol FGs, a quick reaction that is mild enough to be used on living cells. [25][26][27] The combination of those α-oxoaldehyde groups with amino FGs into hydrogel networks, could open a window for an easy yield of chemoselective imine covalent linkages in HGs.…”
The development of new materials with smart properties is currently expanding the development of new technologies. Therefore, the design of materials with novel sensitivities and smart behavior is important for the development of smart systems with automated responsivity. We have recently reported the synthesis of hydrogels, crosslinked by N,N'-diallyltartardiamide (DAT). The covalent DAT-crosslinking points have vicinal diols which can be easily cleaved with periodate, generating changes in the hydrogel properties, as well as generating valuable α-oxo-aldehyde functional groups useful for further chemical modification. Based on those findings, we envisioned that a self-healable hydrogel could be obtained by incorporation of primary amino functional groups, from 2-aminoethyl methacrylate hydrochloride (AEMA), coexisting with DAT into the same network. Herein, α-oxo-aldehyde groups generated after the reaction with periodate would arise in the immediate environment of amine groups to form imine cross-links. For this purpose, DAT-crosslinked hydrogels were synthesized and carefully characterized. The cleavage of DAT-crosslinks with periodate promoted changes in the mechanical and swelling properties of the materials. As expected, a self-healing behavior was observed, based on the spontaneous formation of imine covalent bonds.In addition, we surprisingly found a combination of fast vicinal diols cleavage and a low speed self-crosslinking reaction by imine formation. Consequently, it was found a timewindow in which a periodate-treated polymer was obtained in a transient liquid state, which can be exploited to choose the final shape of the material, before automated gelling. The singular properties attained on these hydrogels could be useful for developing sensors, actuators, among other smart systems.
“…When GTA is added in excess a competitive reaction between GTA and amino groups in the gelatin and between GTA with another GTA molecule takes place. This competitive reaction produces gelatin structures functionalized with free aldehyde chemical groups, which are typically found in their hydrated form (Wolfel et al, 2017), thus reducing water availability and mobility of reactant species in the dosimeters, in spite of the decrease in the elastic modulus. Similar results were obtained in studies of gelatin concentration on AAm and BIS systems (Lepage et al, 2001), where an increase in the rigidity of the structure of the dosimeter due to an increase in gelatin concentration led to a lower sensitivity and higher saturation dose.…”
The use of additives in polymer gel dosimeters to enhance their sensitivity or to improve their performance is of great importance for their application in radiomedicine. Inorganic salts have been used as additives with this purpose; however, their presence in the dosimeters induce severe modifications in their mechanical properties and consequently in their capabilities to maintain a stable dose distribution with time. Most studies in this area conclude in the need to use chemical modifications of the species responsible for the mechanical properties of the dosimeters, which in most cases is a gelatin matrix. In this study, a covalent crosslinking of the gelatin matrix of PAGAT dosimeters doped with different inorganic salts, namely MgCl 2 , CaCl 2 and MnCl 2 has been carried out. The mechanical properties, X-ray sensitivity and dose distribution stability in these materials were compared to those of PAGAT. The results indicated a compromise between the crosslinking of the gelatin structure and the sensitivity of the dosimetric material. Therefore, the proper selection of the degree of crosslinking and the inorganic salt concentration must be considered. An enhanced dosimeter was obtained by adding MgCl 2 with a M 1 concentration and by crosslinking the gelatin matrix with glutaraldehyde at a w v 0.08% / concentration. This material presented a 75% enhanced sensitivity relative to PAGAT and similar temporal stability and spatial stability in 2D dose distributions.
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