Novel pyochelin-based PEGylated liposomes for enhanced delivery of antibiotics against resistant clinical isolates of Pseudomonas aeruginosa

Figures & data

Scheme 1. Synthesis of deprotected functionalized pyochelin (Pch).

Scheme 2. PEGylated liposome complexes stabilized with pyochelin conjugates for specific targeting of P. aeruginosa.

Scheme 3. Illustration of bactericidal activity of PEGylated pyochelin based liposomal antibiotics.

Figure 1. ¹H NMR spectra of the methyl esters of synthesized pyochelin.

Table 1: Concentrations of F-Ab and L-Pch-Ab antibiotics (µg/ml) against ATCC 27853 and three clinical strains of P. aeruginosa (PS75, PS89 and PS103).

	F-CPM	L-PCH-CPM	L-Pch-CPM SM	F-IPM	L-PCH-IPM	L-Pch-IPM SM	F-CAZ	L-PCH-CAZ	L-Pch-CAZ SM
ATCC	7.66 ± 0.57^a	2.33 ± 0.58^a	2.46 ± 0.35^a	2.66 ± 0.57^a	0.66 ± 0.28^a	0.2 ± 0.1^a	12.66 ± 0.57^ab	4.33 ± 0.57^a	4.33 ± 0.32^a
PS75	16.33 ± 1.53^ab	5.01 ± 1.01^a	5.46 ± 0.37^a	4.21 ± 1.26^a	1.66 ± 0.57^a	0.73 ± 0.15^a	17.66 ± 1.54^ab	8.33 ± 0.69^a	6.13 ± 0.25^a
PS89	33.33 ± 1.53^b	16.09 ± 1.26^ab	14.43 ± 0.30^ab	8.42 ± 1.25^a	1.66 ± 0.57^a	1.22 ± 0.24^a	65.33 ± 1.54^b	16.66 ± 1.45^ab	15.46 ± 0.49^ab
PS103	129.33 ± 3.06^bc	16.33 ± 1.52^ab	15.76 ± 0.70^ab	33.66 ± 2.08^b	6.33 ± 1.52^a	2.46. ± ± 0.30^a	1024.54 ± 1.22^c	32.04 ± 2.3^b	32.33 ± 0.29^b

Data are represented as the mean ± SD ^a–bwithin a column, different superscripts indicate significance at p < .05; ^a–cwithin a column, different superscripts indicate significance at p < .05.

Figure 2. Characteristic TEM images of P. aeruginosa treated with various liposomal formulations at 4× MIC concentrations. (A) Bare liposomes, (B) MDRPa strain PS103, 4 h incubation with (C) L-CPM, (D) L-IPM, (E) L-CAZ, (F) L-Pch-CPM, (G) L-Pch-IPM, (H) L-Pch-CAZ and 6 h incubation with (I) L-Pch-CPM, (J) L-Pch-IPM and (K) L-Pch-CAZ.

Figure 3. Time kill curves of (a–c) laboratory strain – ATCC 27853, (d–f) sensitive strain – PS75, (g–i) moderately resistant strain – PS89, (j–l) highly resistant strain – PS103.

Figure 4. In vitro cytotoxicity of L-Pch-Ab formulations on HaCaT cells. HaCaT cells were treated with 4× MIC of L-Pch-CPM for 24, 48 and 72 h and cell viability was determined by MTT assay. Data expressed as a percentage of untreated control cells and are reported as the mean of three independent experiments ± SEM. *indicates a p value of <.05 compared to the corresponding resistant isolate PS103.

Figure 5. Microscopic images of HaCaT keratinocytes. A, Control cells; B, Cells infected with 3 log CFU/ml PS103 for 2 h; C, Cells treated with L-Pch-CPM for 24 h killed the bacterium with reduced toxicity. Scale bar, 50 µm.