Formation and Degradation Tracking of a Composite Hydrogel Based on UCNPs@PDA

Abstract

The constant and noninvasive tracking of the distribution and degradation of engineered hydrogel scaffolds using fluorescent probes is considered to be one of the important research studies. Conventional fluorophores were simply mixed into hydrogels by physical doping, and they suffered from photoinstability or UV–vis light excitation, which usually led to the potential leak of the fluorescent tag and imprecise tracking results. In this article, upconversion nanoparticles, NaGdF4:Yb3+,Er3+@NaGdF4 (UCNPs) with near-infrared light (NIR) excitation, were synthesized and were coated with polydopamine (PDA). A biodegradable composite hydrogel OSA-I-CMCS-I-UCNPs@PDA (“I” means “linked-by”) was constructed by the UCNPs@PDA, serving as both the construction unit and NIR-excited fluorescent probe, where carboxymethyl chitosan (CMCS) was used as the cross-linker to chemically cross-link UCNPs@PDA and oxidized sodium alginate (OSA) based on dynamic covalent Schiff-base linkages. It is demonstrated that the composite hydrogels possess enhanced mechanical strength, excellent self-healing capacity, injectable performance, and good biocompatibility with the tissue. In addition, the composite hydrogels possess a deep penetrating ability from UCNPs@PDA in vitro through about 10 mm thick chicken strips. A mimetic lysozyme biodegradation test was performed for 108 h in vitro for evaluating the feasibility and accuracy of UCNPs@PDA in tracking the hydrogel degradation. The degradation signals were obtained by the decrease in fluorescence intensity, which were well consistent with the weight changes in composite hydrogels, suggesting the accuracy of the UCNPs@PDA in consecutively monitoring the hydrogel degradation in vitro. With these superior properties, the composite hydrogels are expected to be promising candidates for various biomedical fields, for example, as tissue engineering or delivery carriers in vivo.

Photovoltaic Energy Conversion and Storage of Micro-Supercapacitors Based on Emulsion Self-Assembly of Upconverting Nanoparticles

“…The OA-stabilized lanthanide-doped upconversion nanoparticles, NaGdF 4 : 20% Yb 3+ , 2% Er 3+ were synthesized by a thermal decomposition method with modification of our previous works. 24 − 26 The TEM image of the UCNPs in Figure 1 a suggests that the nanoparticles are uniform and have an average diameter of about 16.6 nm determined by random measurement of 100 particles. These prepared UCNPs are used as building blocks to fabricate assemblies of SPs based on a surfactant-assisted emulsion self-assembly method.…”

“… 11 Lanthanide-doped upconversion luminescent materials with multiple 4f electronic energy states can absorb near-infrared (NIR) light and emit visible light, exhibiting extensive applications from bioimaging to photovoltaic technologies. 24 Recent research on upconversion materials mainly focuses on the luminescent property, while the excellent photovoltaic property acting as electrode materials has not been thoroughly explored. As a kind of photovoltaic material, UCNPs capped with OA ligands are supposed to be promising building blocks to fabricate MSCs by self-assembling into hollow superlattice assemblies.…”

Enzyme-Regulated Healable Polymeric Hydrogels

“… The concepts of extrinsic and intrinsic self-healing materials − became clear in early 21st century, after the successful exploitations of microcapsule-based/microvascular self-healing materials, , and Diels–Alder reaction-based thermal-triggered self-healing polymers . Nowadays, synthetic self-healing materials can not only repair the structural defects and restore the mechanical properties ,− but also recover the material functions including transparency, , electrical conductivity, − hydrophobicity, superhydrophobicity, − and antifouling functions. , Despite these achievements, current synthetic self-healing materials are still far less intelligent and practical than self-healable living organisms.…”

“…Since the first hydrogel was synthesized by Wichterle and Lim in 1960 (Figure ), these soft materials have made a significant impact on the developments of electronic sensors, , lyotropic liquid crystals, smart windows, drug/cell delivery systems, − and scaffolds for tissue engineering. ,− Polymeric hydrogels comprise chemically or physically cross-linked polymer networks and large portions of water, which not only enable the design of reversible interactions in the cross-linked networks for self-healing but also provide a suitable environment to facilitate the occurrence of enzymatic reactions. ,− The initial use of enzymatic reactions in polymeric hydrogels is for material construction, − and then followed by enzymatic fabrication of healable polymeric hydrogels ,− and enzymatically regulated healing of polymeric hydrogels. ,, The latest progress of this field is to use the enzymatic reaction to mediate the transient healing ability of polymeric hydrogels, , which not only enables the fabrication of thermodynamically stable and kinetically inert hydrogels but also endows such hydrogels with an intrinsic healing ability on demand.…”

Tuning polymers grafted on upconversion nanoparticles for the delivery of 5-fluorouracil

“…Wu et al have removed the oleic acid ligands from the surface of UCNPs by acid treatment to induce the electrostatic adsorption of dopamine that was polymerized under oxidative conditions. [17] UCNPs have also been explored to trigger photopolymerization upon NIR irradiation in the presence of Eosin Y as photoinitiator to prepare crosslinked polymers at the surface of UCNPs. [18,19] Ricinoleic acid has been used as ligand to prepare UCNPs bearing hydroxyl groups able to initiate cationic ring-opening polymerization from the surface of UCNPs for the synthesis of hyperbranched polyglycerol [20,21] and linear poly(ε-caprolactone) [21] affording UCNPs with high water dispersibility and upconversion luminescence.…”