Marrying the incompatible for better: Incorporation of hydrophobic payloads in superhydrophilic hydrogels

Ag/Au-incorporated trimethyl chitosan-shell hybrid particles as reinforcing and antioxidant fillers for trimethyl chitosan hydrogel

N,N,N-Trimethyl chitosan (TMC) is a quaternized chitosan with versatile biological features. However, low mechanical strength limits its uses, for example, as hydrogels for tissue engineering applications. This study illustrates a viable synthesis of metal/polymer hybrid, core-shell colloidal particles and their use as reinforcing and antioxidant fillers for TMC hydrogels. The core-shell particles were initially synthesized by surfactant-free emulsion polymerization, induced by a photo-redox initiating system of riboflavin assisted by a 3° amine and 2° alcohol co-initiators. The synthesized core-shell particles were based on two polymeric shells: TMC and chitosan, and two polymeric cores: poly (hydroxypropyl methacrylate) (PHPMA) and poly(2-hydroxy ethyl methacrylate) (PHEMA). The presence of both 3° amine on TMC and 2° alcohol on HPMA monomer enhanced the photopolymerization performance. The TMC-based particles had sizes of 122-154 nm and zeta potentials of 10-35 mV, bringing the colloidal stability in the 4-10 pH range. Furthermore, due to the presence of TMC on the shell layer, the core-shell particles could be used as templates to grow the Ag/Au bimetallic nanoparticles with alloy and core-shell types through a thermal reduction. The prepared hybrid particles were incorporated in TMC hydrogels as a multifunctional filler, improving their mechanical and antioxidant properties.

UCNPs-labeled electrospun scaffolds used to monitor in vivo degradation and bone tissue regeneration

Biodegradable electrospun bone repair materials are effective means to treat bone defects. However, because the electrospun substrates are mostly organic polymer materials, there is a lack of real-time and intuitive monitoring methods for their degradation in vivo. Therefore, it is of great significance to develop in vivo traced electrospun bone repair materials for postoperative observation of their degradation. In this research, polycaprolactone/up-conversion nanoparticles/magnesium oxide (PCL/UCNPs/MgO) composite scaffolds were prepared by electrospun based on the luminescence characteristics of up-conversion nanoparticles (UCNPs) under near infrared excitation and the osteogenic ability of MgO. The in vivo and in vitro degradation results showed that with the increase of time, the electrospun scaffolds gradually degraded and its luminescence intensity decreased. The addition of UCNPs can effectively monitor the degradation of the scaffolds. In addition, the prepared electrospun scaffolds had great biocompatibility, among which PCL-1%UCNPs-1%MgO (P1U1M) electrospun scaffolds had obvious effect on promoting osteogenic differentiation of mouse embryonic osteoblasts cells (MC3T3-E1) in vitro. In conclusion, P1U1M electrospun scaffolds have the potential to induce bone regeneration at bone defect sites, and can monitor the degradation of electrospun scaffolds. It may be a potential candidate material for bone regeneration in defect area.

Nanofibers as precursors for the rapid formation of hydrogels

Hydrogels can be used in surgeries, which require a support material to maintain the correct anatomy. One major limitation is however the time required for the preparation of hydrogels under urgent conditions. Herein, we report a new method for a very fast preparation of hydrogels at room temperature. Nanofibers of dextran containing vinyl groups produced by electrospinning are loaded with redox- or photo-initiators for radical polymerization. Once dissolved in water, the nanofibers yield hydrogels either spontaneously or upon irradiation with UV light. We also show that the nanofibers can be loaded with active fillers so that hydrogels embedding nanocapsules are obtained. This concept could be applied for the rapid preparation of functional hydrogels which are needed as implants.

Injectable hydrogel imbibed with camptothecin-loaded mesoporous silica nanoparticles as an implantable sustained delivery depot for cancer therapy

In recent years, injectable stimuli-sensitive hydrogels are employed as suitable drug delivery carriers for the release of various anti-cancer drugs. However, large pore size of the microporous hydrogel trigger release of small molecular anticancer drug that limits hydrogel application in cancer therapy. Therefore, introducing reinforcing fillers such as mesoporous silica nanoparticles (MSNs) can not only load different type of anticancer drugs but also prevent the premature release of drugs due to the strengthening of the networks. Furthermore, high specific surface area, suitable size, large pore volume, and stable physicochemical properties of MSNs can improve the therapeutic efficacy. In this study, to sustain the release of hydrophobic anticancer drug, camptothecin (CPT) was loaded into MSNs, and then imbibed into the physiological stimuli-sensitive poly(ethylene glycol)-poly(β-aminoester urethane) (PAEU) hydrogels. MSN-imbibed PAEU hydrogels exhibited prolonged release of CPT than MSNs and PAEU hydrogel alone. Furthermore, MSN-imbibed PAEU copolymers form stable viscoelastic gel depot into the subcutaneous layers of Sprague-Dawley rats and found to be safe and not induced toxicity to healthy organs, implying biodegradability and safety of the hydrogels. Interestingly, CPT-loaded hydrogels shown dose-dependent toxicity to A549 and B16F10 cells. These results demonstrated that MSN-imbibed PAEU hydrogel with biocompatible, biodegradable, and in situ gel forming property could be a useful drug delivery depot for sustained release of anticancer drugs.