Elastin-like polypeptide incorporated thermally sensitive liposome improve antibiotic therapy against musculoskeletal bacterial pathogens

Figures & data

Table 1. Design and composition of ELP-TSL library.

	ELP-TSL (Mole ratio)
Components	ELP-TSL (100:0):15	ELP-TSL (75:25):15	ELP-TSL (75:25):25
DPPC	55	41.25	41.25
DSPC	0	13.75	13.75
DSPE-PEG2000	2	2	2
Cholesterol	15	15	25
MSPC	0	0	0
ELP	0.41	0.41	0.41

Table 2. Particle size and zeta potential of cipro loaded ELP-TSL library.

		Zeta-potential (mV)
Liposomes	Hydrodynamic Diameter (nm)	PBS	ddH2O	Encapsulation efficiency (%)
ELP-TSL (100:0):15	154 ± 2.6	−35 ± 1.9	−1.0 ± 2.5	29.2
ELP-TSL (75:25):15	165 ± 3.3	−38 ± 1.5	−0.7 ± 2.4	68.5
ELP-TSL (75:25):25	169 ± 1.1	−43 ± 1.4	−0.8 ± 1.7	46.5

Figure 1. Thermoscan assay in physiological buffer containing 25% serum for cipro loaded ELP-TSL prepared with a different molar ratio of DPPC: DSPC ratio (100:0 and 75:25) and cholesterol (15 and 25 molar ratio). ELP-TSL were tuneable and shifted transitional temperature and temperature of maximum drug release depending on lipid composition.

Figure 2. Thermogram of ELP-TSLs and LTSLs. There was no sharp peak of transition in ELP-TSLs, however, a progressive increase in heat flow was noted for 75:25:25:0.4.

Figure 3. TEM images of LTSL and ELP-TSL (DPPC:DSPC: Cholesterol: 75:25:15 molar ratio) loaded with cipro. Crystallized cipro is seen within the core of the liposomes (arrows).

Figure 4. Release kinetics of ELP-TSL (DPPC:DSPC: Cholesterol:75:25:15 molar ratio) in PBS containing 25% FBS. ELP-TSL were incubated in 25% FBS for 30 min. At 37 °C, within 5 min. of incubation in 25% serum, ELP-TSL maintained stability and retained >90% of cipro. After 15–30 min. of incubation, ELP-TSL retained greater than 50–60% of the content at body temperature and achieve near complete release at hyperthermia.

Figure 5. (a) Evaluation of thermosensitive release and killing of S. aureus and P. aeruginosa treated with ELP-TSL (DPPC:DSPC: Cholesterol:75:25:15 molar ratio) in 25% FBS, by disc diffusion method. The amount of drug on the disc ranges from 0 to 5 μg (b) Zones of inhibition for S. aureus and P. aeruginosa respectively. Bacterial killing was observed only at 39 °C and 42 °C. (c) Evaluation of toxicity of bland liposomes. No zone of inhibition was observed for S. aureus or P. aeruginosa, respectively, treated with TSL (without ELP) and bland ELP-TSL liposomes.

Figure 6. Percentage killing of methicillin-resistant S. aureus (MRSA) treated with Cipro loaded ELP-TSL at 37 °C and 42 °C. ELP-TSL (DPPC:DSPC:Cholesterol: 75:25:15 molar ratio); in combination with mild hyperthermia significantly improved killing of MRSA compared to 37 °C. Cipro alone demonstrated similar efficacy at 37 °C and 42 °C since the free drug was freely available to the bacteria.