Self-assembled organic aggregates are encapsulated into polymersomes, also formed by self-assembly, to form novel hierarchical nanocomposite materials with exceptionally high payloads for advanced function. Clinical translation of photoacoustic imaging (PAI) has been limited by the lack of sensitive near infrared (NIR) contrast agents with low toxicity. Herein, 50 nm “J aggregates” of FDA approved indocyanine green (ICG) with strong NIR absorbance were encapsulated at high loadings up to 70% within small 77 nm polymersomes (nanocapsules) composed of poly(lactide-co-glycolide-<i>b</i>-polyethylene glycol) (PLGA-b-PEG) bilayers. During self-assembly of the polymersomes, loss of ICG from the ICG J aggregates was minimized by strategic design of the various interfacial interactions to control the dewetting of the polymersomes from oil droplets dispersed in water. The high loadings enabled PAI of of cancer cells with high specificity and a high detection limit. The encapsulated J aggregates were protected against dissociation by the polymersome shell for more than 24 hours in 100% fetal bovine serum enabling cancer imaging. The self-assembly concepts in this study may be generalized to design numerous types of hierarchical polymersomes with high payloads of targeted drugs and imaging agents which can lead to chemo-photothermal therapeutics in addition to photoacoustic imaging for cancer.

Self-assembled organic dye aggregates in polymersomes with high loadings

ACS Spring Meeting 2021

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