Preparation And Characterization Of Bacterial Cellulose Antimicrobial Dressings

Bacterial cellulose（BC） is a kind of natural polymer material with unique three-dimensional network structure in nano-scale, which makes it has unique physical and chemical properties, such as high crystallinity, high mechanical strength, high water holding capacity, good biocompatibility and biodegradability. BC is considered to be a natural biomedical dressing which can provide a moist environment for the wound and absorb wound exudate. However, BC itself does not possess antibacterial properties. Bacterial cellulose antibacterial dressings are prepared by compositing BC and antibaterial agents.Polyhexamethylene biguanidine hydrochloride（PHMB） is a broad spectrum antibacterial agent. BC/PHMB antibacterial dressings were firstly prepared and characterized. Then, BC/PHMB were compared with BC/Ag NPs and BC/Cu₂O composits. Through the performance comparison, we can get the dressing with lower cost and better antibacterial properties.BC/PHMB composites were prepared by physical impregnation. BC/Ag NPs and BC/Cu₂O composites were prepared by chemical reduction method. The detail researches are as follows:（1） Preparation and characterization of BC/PHMB antibacterial dressings: BC/PHMB composits were prepared by immersing wet BC pellicle into PHMB aqueous solution. The structure of BC/PHMB was characterized by scanning electron microscopy（SEM） and fourier transform infrared spectroscopy（FT-IR）. Mechanical property, water management system, drug release mechanism and antibacterial performance were analyzed by comparing with bacterial cellulose which served as control sample. The results revealed that: with the increase of the concentration of PHMB, the drug content increased from 371 mg/100cm² to 842 mg/100cm². According to the Peppas-Ritger equation, the drug release mechanism of BC/PHMB antimicrobial dressings was Fickian release: drug release under diffusion control. While BC had no antibacterial effect on Escherichia coli and Staphylococcus aureus, BC/PHMB had excellent antibacterial effect on both bacterials. When PHMB concentration increased from 1.0wt% to 2.0wt%, the drug loading amount, cumulative release amount and antibacterial band width had almost no increase. Considering the cost, BC/PHMB（1.0wt%） antibaterial dressings have optimal performance.（2） Preparation and characterization of BC/Ag NPs antibacterial dressings: using BC as reducing agents with different concentration of AgNO₃ at 0.205 MPa and 121 ℃ for 10 min. The structure of BC/Ag NPs was characterized by scanning electron microscopy（SEM） and UV-visible spectral analysis. Mechanical properties, water management system, drug release mechanism and antibacterial performance were also analyzed. The results revealed that silver nanoparticles could be prepared by green synthesis method. The silver nanoparticles were spherical or nearly spherical with the face-centred cubic（fcc） geometry. Silver nanoparticles were uniformly distributed in the three-dimensional network structure of BC. With the increase of the concentration of AgNO₃, the silver content increased from 24 mg/100cm² to 127 mg/100cm² and the size of silver nanoparticles increased. The drug release mechanism of BC/ Ag NPs antimicrobial dressings was Fickian release. BC/Ag NPs antibacterial dressings had excellent antibacterial effect on both Escherichia coli and Staphylococcus aureus. BC/Ag NPs（1.0wt%） had the best antibaterial properties, which was better than BC/PHMB（1.0wt%）.（3） Preparation and characterization of BC/Cu₂O antibacterial dressings: using BC as reducing agents with different concentration of Cu²⁺ and Na OH at 0.205 MPa and 121 ℃ for 30 min. The structure of BC/ Cu₂O was characterized by scanning electron microscopy（SEM） and X-ray diffractometry（XRD）. Mechanical properties, water management system, drug release mechanism and antibacterial performance were also analyzed. The results showed that Cu₂O were octahedral, the edge length was about 750 nm. With the increase of the concentration of Cu²⁺, the Cu₂O content increased from 51 mg/100cm² to 81 mg/100cm². The drug release mechanism of BC/Cu₂O antimicrobial dressings was Fickian release. BC/Cu₂O antibacterial dressings had excellent antibacterial effect on both Escherichia coli and Staphylococcus aureus. The antibacterial band width of was between 0.15-6.71 mm. BC/Cu2O（5wt%） had the best comprehensive performance. Compared with BC/PHMB（1.0wt%） and BC/Ag NPs（1.0wt%）, BC/Cu2O（5wt%） had the best antibacterial property and the lowest cost.