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Reversible size changes in degradable nanoparticles composed of bio-based cinnamate derivative copolymers, poly(3,4-dihydroxycinnamic acid-co-4-hydroxycinnamic acid) [P(3,4DHCA-co-4HCA)], were observed for the first time. The 860 nm diameter decreased to almost one-half (420 nm) during UV irradiation over 280 nm and rapidly recovered to 620 nm upon subsequent irradiation at 254 nm. Results from UV−vis and 1H NMR spectra suggested that diameter-changing phenomena corresponded to [2 + 2] cycloaddition formation and cleavage of the cinnamate groups. This significant diameter change was reproduced for at least three cycles, and the reason for this significant size change seemed to be due to the fact that all units of the copolymer contained photochromic groups. Furthermore, these photo-cross-linked bio-based nanoparticles showed various size change behaviors during hydrolytic degradation depending on the degree of cross-linking. Photosensitive degradable nanoparticles may be useful as novel, size-controllable carriers for environmental and biomedical fields.

To enhance the glucose sensitivity and self-regulated release of insulin, biobased capsules with glucose-responsive and competitive properties were fabricated based on poly(γ-glutamic acid) (γ-PGA) and chitosan oligosaccharide (CS) polyelectrolytes. First, poly(γ-glutamic acid)-g-3-aminophenylboronic acid) (γ-PGA-g-APBA) and galactosylated chitosan oligosaccharide (GC) were synthesized by grafting APBA and lactobionic acid (LA) to γ-PGA and CS, respectively. The (γ-PGA-g-APBA/GC)5 capsules were then prepared by layer-by-layer (LBL) assembly of γ-PGA-g-APBA and GC via electrostatic interaction. The size and morphology of the particles and capsules were investigated by DLS, SEM, and TEM. The size of the (γ-PGA-g-APBA/GC)5 capsules increased with increasing glucose concentration due to the swelling of the capsules. The capsules could be dissociated at high glucose concentration due to the breaking of the cross-linking bonds between APBA and LA by the competitive reaction of APBA with glucose. The encapsulated insulin was able to undergo self-regulated release from the capsules depending on the glucose level and APBA composition. The amount of insulin release increased with incubation in higher glucose concentration and decreased with higher APBA composition. Moreover, the on-off regulation of insulin release from the (γ-PGA-g-APBA/GC)5 capsules could be triggered with a synchronizing and variation of the external glucose concentration, whereas the capsules without the LA functional groups did not show the on-off regulated release. Furthermore, the (γ-PGA-g-APBA/GC)5 capsules are biocompatible. These (γ-PGA-g-APBA/GC)5 with good stability, glucose response, and controlled insulin delivery are expected to be used for future applications to glucose-triggered insulin delivery.

Gold nanorods (AuNRs) are confirmed to have excellent and repeated photothermal properties under near-infrared (NIR)-light irradiation above 780 nm. However, AuNRs easily leaked out from local pathological tissues and circulated in the body, reducing photothermal therapy (PTT) efficacy. By complexing AuNRs with a scaffold via interactions, AuNRs might be dispersed in the scaffold and fixed in the tumor site. Thus, based on the mussel-mimetic adhesion concept, AuNRs were designed to be coated with polydopamine (PDA), and then the prepared polydopamine-coated AuNRs (AuNR-PDA) were incorporated into a thermosensitive injectable hydrogel composed of β-glycerophosphate-bound chitosan (CGP) and dopamine-modified alginate (Alg-DA) efficiently. Due to the strong interactions between PDA and polymers, AuNR-PDA could be immobilized stably and evenly into the obtained CGP/Alg-DA/AuNR composite hydrogel, which can avoid overheating locally or leaking out. The sol–gel transition temperature of the composite hydrogel was adjusted to the body temperature at around 37 °C to be conveniently injectable in vivo. With NIR irradiation at 808 nm of wavelength, the composite hydrogel was locally heated quickly to over 50 °C depending on controlling the irradiation powers and times. Moreover, the in vitro cytotoxicity test of the composite hydrogel showed good biocompatibility to normal cells but obvious suppression to tumor cells’ growth under multiple times of photothermal therapy. Furthermore, the in vivo antitumor test demonstrated the obvious suppression to tumor growth of the CGP/Alg-DA/AuNR composite hydrogel under multiple PTTs. Therefore, the injectable CGP/Alg-DA/AuNR hydrogel could be a promising candidate for the long-term repeated photothermal treatment of tumors.