Synthesis and Self-assembly Behavior of Porphyrin-based Polypeptides
Poly(y-benzyl-L-glutamate)(PBLG)with propargyl terminal group and porphyrin derivatives containing single azide group(TFPP-N3)were used as reactants to synthesize porphyrin-based polypeptide(TFPP-PBLG)using a click reaction.The molecular structures of the polymers,including molecular weight,polydispersity index,and composition were characterized by nuclear magnetic resonance spectroscopy(1H-NMR),Fourier transform infrared spectroscopy(FTIR),ultraviolet-visible spectrophotometer(UV-Vis),and gel permeation chromatography(GPC).The critical water content(CWC)for the aggregation of the TFPP-PBLG polymers was determined by turbidity measurement(OD).By a selective precipitation method with water as the selective solvent,bowl-like aggregates with obvious pits were obtained.The solution self-assembly behavior was studied by scanning electron microscopy(SEM),atomic force microscopy(AFM),transmission electron microscopy(TEM),dynamic laser light scattering(DLS)and small-angle X-ray scattering(SAXS).The results show that the TFPP-PBLG polymers can self-assemble into bowl-like aggregations when the PBLG chain is relatively short.Upon the addition of water,solubility of the solvent for polymers decreases,and the polymers aggregate into micelles.Theπ-π stacking effect contributed by porphyrin derivatives results in a relatively stable structure of the micelles.During the dialysis process,the solvent within the micelle diffuses outward while water is difficult into the micelles,causing the micelle to collapse and form a pit structure.As the solvent further diffuses,the pit becomes larger,ultimately leading to a bowl-like aggregate structure.Increasing the length of the PBLG makes the initial micelles more stable,which inhibits the collapse of the micelles under the dialysis process,as a result,ellipsoid micelles are maintained.The stability of the initial formed micelle is crucial in determining whether it undergoes depression during the subsequent dialysis process,ultimately resulting in the formation of nanobowls.
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