Development of an anti-microbial peptide-mediated liposomal delivery system: a novel approach towards pH-responsive anti-microbial peptides

Figures & data

Figure 1. (A) The serum turbidity monitoring after mixing liposomes with serum of the same volume and incubated under 37 °C. (B) The cellular uptake of D-Lip with different amount of DSPE-PEG₂₀₀₀-[D]-H₆L₉ in the lipid constitution. The horizontal ordinate suggested the ratio of DSPE-PEG₂₀₀₀-[D]-H₆L₉ in total lipid.

Table 1. The size and the zeta potential measurement of PEG-Lip and D-Lip under different pH conditions when the amount of the DSPE-PEG₂₀₀₀-[D]-H₆L₉ was 6% in the total lipids.

	Size (nm)	PDI	Zeta potential (mV)
PEG-Lip (pH 7.4)	92.6 ± 4.6	0.256 ± 0.07	−6.3 ± 1.2
PEG-Lip (pH 6.3)	90.1 ± 4.2	0.206 ± 0.09	−5.3 ± 0.9
D-Lip (pH 7.4)	110.8 ± 3.5	0.266 ± 0.13	−2.2 ± 0.8
D-Lip (pH 6.3)	103.2 ± 3.6	0.219 ± 0.09	9.2 ± 1.1

Figure 2. Parts (A) and (B) represent the cellular uptake on C26 cells of PEG-Lip and D-Lip under pH 7.4 and pH 6.3 determined by confocal microscopy and flow cytometry. (C) The cytotoxicity of blank D-Lip of different concentrations under both pH 7.4 and 6.3. The horizontal ordinate indicated the final total lipid concentration of liposomes in culture medium.

Figure 3. The uptake of CFPE-labeled D-Lip under both pH 7.4 and 6.3 within different depths into the tumor spheroid. The scale bars represent 250 μm.

Figure 4. (A) The subcellular localization on C26 cells of CFPE-labeled liposomes (A2 and A6) and lysosomes (A3 and A7). Nuclei were stained by DAPI (A1 and A5). Scale bars represented 10 μm. (B) Cellular uptake of CFPE-labeled D-Lip on C26 cells inhibited by different factors. *indicates the significance between group Normal and all the other groups.

Figure 5. Biodistribution assay of D-Lip on C26 tumor-bearing Balb/C mice. Parts (A) and (B) display the in vivo and ex vivo fluorescent biodistribution of DiR-loaded liposomes; the black arrows in (A) indicated the location of the C26 tumor. (C) The quantitative determination of tumor uptake of DiD-loaded liposomes is shown, *indicating the significance between PEG-Lip and D-Lip and (D) the confocal images of tumor frozen sections are shown. Bars represent 50 μm.