Preparation of total flavonoid-liposomes of Lonicerae Japonicae flos and their inhibitory effect on methicillin-resistant Staphylococcus aureus

To prepare the liposomes of total flavonoids from Lonicerae Japonicae flos (LJFTF) and evaluate their inhibitory effect on methicillin-resistant Staphylococcus aureus(MRSA).

LJFTF liposomes were prepared by ethanol injection.Then the preparation process was optimized by star point design-effect surface method, with the concentrations of phospholipid, mass ratio of phospholipid to cholesterol and mass concentration of LJFTF as the influencing factors, and the encapsulation rate and drug-loading rate as evaluation indicators.The obtained liposomes were characterized by observing their properties, measuring particle size, polymer dispersity index (PDI) and Zeta potential through laser particle size analyzer.High performance liquid chromatography (HPLC) was used to determine the release rate of the liposomes.The antibacterial activity of the liposomes against MRSA was observed by plate method and live/dead staining, and the inhibitory effect of the liposomes on MRSA biofilm was observed by crystal violet staining.

After optimization and verification, the best preparation process was as follows: phospholipid concentration 35.0 mg/mL, phospholipid to cholesterol mass ratio 15.0, and LJFTF concentration 5.7 mg/mL.The prepared liposomes were light yellow emulsion, with an average encapsulation rate of 86.37%(RSD=0.37%, n=3), and an average drug-loading rate of 11.69%(RSD=0.09%, n=3), a particle size of 173.60±1.07 nm, a PDI value of 0.15±0.05, and a Zeta potential of-4.86±0.60 mV.The free LJFTF was completely released within 4 h from the dialysis bag, and the in vitro cumulative release of LJFTF was (59.44±3.58)% at 12 h and (63.58±5.78)% at 30 h.Plate and live/dead staining showed that the prepared liposomes significantly inhibited the growth and promoted the death of MRSA strain.Crystal violet staining displayed that the liposomes significantly inhibited the formation of MRSA biofilm (P < 0.001), with significant difference in comparison with same dose of LJFTF (P < 0.001).

LJFTF liposomes are successfully prepared, and the formulation process has been optimized.The liposomes show significant anti-MRSA activity in vitro.