pH-Responsive Polyethylene Glycol Monomethyl Ether-ε-Polylysine-G-Poly (Lactic Acid)-Based Nanoparticles as Protein Delivery Systems

<div><p>The application of poly(lactic acid) for sustained protein delivery is restricted by the harsh pH inside carriers. In this study, we synthesized a pH-responsive comb-shaped block copolymer, polyethylene glycol monomethyl ether-ε-polylysine-<i>g</i>-poly (lactic acid) (PEP)to deliver protein (bovine serum albumin (BSA)). The PEP nanoparticles could automatically adjust the internal pH to a milder level, as shown by the quantitative ratio metric results. The circular dichroism spectra showed that proteins from the PEP nanoparticles were more stable than those from poly(lactic acid) nanoparticles. PEP nanoparticles could achieve sustained BSA release in both <i>in vitro</i> and <i>in vivo</i> experiments. Cytotoxicity results in HL-7702 cells suggested good cell compatibility of PEP carriers. Acute toxicity results showed that the PEP nanoparticles induced no toxic response in Kunming mice. Thus, PEP nanoparticles hold potential as efficient carriers for sustained protein release.</p></div

WU, LC, zeta potential, and particle size of NPs.

<p>WU, LC, zeta potential, and particle size of NPs.</p

TEM image of PEP NPs.

<p>TEM image of PEP NPs.</p

Protein release profiles and MTT assay of PEP NPs in the HL-7702 cell line.

<p>Protein release profiles of (a) PLA NPs, (b) PEP NPs, Cell viability result of (c) PLA NPs, (d) EPL, (e) PEP NPs. Cell viability was determined via MTT assay and expressed as a percentage of the control (100% of longitudinal coordinate).</p

H&E-stained section of the liver, spleen, and kidney after injection of PEP52 NPs <i>in vivo</i>.

<p>H&E-stained section of the liver, spleen, and kidney after injection of PEP52 NPs <i>in vivo</i>.</p

Kinetic fitting results of BSA released from nanoparticles with different kinetic models.

<p>Kinetic fitting results of BSA released from nanoparticles with different kinetic models.</p

Structure of the amphiphilic comb-shaped copolymer PEP and biodegradation properties of PEP nanoparticles.

<p>(a) 1H-NMR spectrum of PEP in DMSO-d6; (b) 1H-NMR spectrum of PEP NPs in D2O; (c) chemical composition percentages of azote on the surface of different NPs; (d) Biodegradation properties of PEP and PLA NPs in PBS (0.1 M, pH 7.4) at 37°C.</p

AUC values of BSA-FITC-loaded formations and free BSA-FITC in the tissues and blood of Kunming mice (n = 10).

<p>AUC values of BSA-FITC-loaded formations and free BSA-FITC in the tissues and blood of Kunming mice (n = 10).</p

Acute toxicity of PEP52 NPs, PLA NPs, and EPL.

<p>Acute toxicity of PEP52 NPs, PLA NPs, and EPL.</p

Materials prepared with reagents of different molar ratios.

<p>Materials prepared with reagents of different molar ratios.</p