pH and light‐responsive polycaprolactone/curcumin@zif‐8 composite films with enhanced antibacterial activity

Abstract

Food packaging materials, especially biodegradable polymer composites incorporated with natural antimicrobial agents with excellent antibacterial activities, are in high demand and attracted immense attention. Herein, a polycaprolactone/curcumin@zeolitic imidazolate framework-8 (PCL/Cur@ZIF-8) composite film with enhanced antibacterial activity was developed. Curcumin, a natural photosensitizer, was loaded in the highly porous nanocrystals ZIF-8 to improve its poor water solubility and stability. The integral structure of Cur@ZIF-8 was maintained well in the PCL matrix even at the highest loading of 35% (w/w), and all composite films had good light transmittance at 420-430 nm. The PCL/Cur@ZIF-8 composite films responded to the acidic growth environment of bacteria by releasing zinc ions and curcumin molecules. Furthermore, upon blue light irradiation (420-430 nm, 2.2 mW/cm 2 ), curcumin molecules generated singlet oxygen. With the synergistic effects of zinc ions and singlet oxygen, the composite films exhibited a 99.9% reduction of Escherichia coli and Staphylococcus aureus strains when the amount of Cur@ZIF-8 loading was more than 15% (w/w), as well as a strong anti-adhesion effect on bacteria. Moreover, bacterial resuscitation tests indicated that the composite films exhibited 99.9% reduction in the adhered bacteria population through treatment with photodynamic sterilization. This is the first study presenting that the incorporated curcumin ZIF-8 nanoparticles in the matrix of polymer are pH and light responsive for anti-adhesion of bacteria, which is of great potential application as antibacterial packaging material for the food industry.

pH-responsive curcumin-based nanoscale ZIF-8 combining chemophotodynamic therapy for excellent antibacterial activity

“…Similar results showed that blue light-activated CCM displayed a remarkable antibacterial activity against Shigella exneri, E. coli and S. aureus. 24,25 Besides, as depicted in Fig. 5C-F, colony counts of blue light-activated ZIF@CCM against E. coli and S. aureus strains obviously decreased compared with that of blue light-activated CCM, further demonstrating that ZIF@CCM-mediated photodynamic therapy exhibited the prominent bacteriostatic effects.…”

“…The phototoxicity of CCM blocked bacterial growth by the autoxidation mechanism of CCM. 25,26 Light irradiation could activate photosensitizers to induce reactive oxygen species (ROS), including singlet oxygen and superoxide. 12 ROS could result into bacterial death by oxidizing components of cell membrane and guanosine in DNA and RNA.…”

“…CCM-loaded ZIF-8 was synthesized in one step method as previously described. 25,34 In brief, a stock solution of 30 mg mL À1 ZnNO 3 $6H 2 O was prepared freshly. Subsequently, 5 mL ZnNO 3 $6H 2 O stock solution was added into 10 mL of methanoldispersed 2-methyl imidazole (330 mg) and CCM (5 mg) with sonication for 10 min.…”

“…The phototoxicity of CCM blocked bacterial growth by the autoxidation mechanism of CCM. 25,26 Light Fig. 5 The bacterial survival rate after logarithmic of E. coli (A) and S. aureus (B) cotreatment with CCM, ZIF-8 and ZIF@CCM and irradiated blue light and dark.…”

Multimodal Antibacterial Platform Constructed by the Schottky Junction of Curcumin‐Based Bio Metal–Organic Frameworks and Ti3C2Tx MXene Nanosheets for Efficient Wound Healing

“…The inhibitive effect is attributed to Zn 2+ ions and curcumin released from Zn‐MOF. [ 58 ] However, the bacteria could be proliferated again after 6 h. Apparently, the two antibacterial agents cannot completely eradicate the bacteria. The Zn‐MOF NIR(+) antibacterial system exhibits a similar antibacterial activity as the Zn‐MOF NIR(−) group (Figure 5d).…”