Bioengineered bacterial vesicles as biological nano-heaters for optoacoustic imaging

Advances in genetic engineering have enabled the use of bacterial outer membrane vesicles (OMVs) to deliver vaccines, drugs and immunotherapy agents, as a strategy to circumvent biocompatibility and large-scale production issues associated with synthetic nanomaterials. We investigate bioengineered OMVs for contrast enhancement in optoacoustic (photoacoustic) imaging. We produce OMVs encapsulating biopolymer-melanin (OMVMel) using a bacterial strain expressing a tyrosinase transgene. Our results show that upon near-infrared light irradiation, OMVMel generates strong optoacoustic signals appropriate for imaging applications. In addition, we show that OMVMel builds up intense heat from the absorbed laser energy and mediates photothermal effects both in vitro and in vivo. Using multispectral optoacoustic tomography, we noninvasively monitor the spatio-temporal, tumour-associated OMVMel distribution in vivo. This work points to the use of bioengineered vesicles as potent alternatives to synthetic particles more commonly employed for optoacoustic imaging, with the potential to enable both image enhancement and photothermal applications.


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April 2018
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Animal procedures were approved by the Government of Upper Bavaria. Sample sizes were chosen based on guidance from the literature. Investigators were not blinded to the identity of groups. For all animal studies, animals of the same gender, age, and genetic background were randomized for grouping. Statistical analyses were performed using SPSS 18.0 (IBM, Chicago, IL, USA). Inter-group differences were assessed for significance using the paired t test. Mean values and error bars are presented as mean ± SD and differences were considered significant if ***p < 0.001.
Data exclusions Animal procedures were approved by the Government of Upper Bavaria. Sample sizes were chosen based on guidance from the literature.
Investigators were not blinded to the identity of groups. For all animal studies, animals of the same gender, age, and genetic background were randomized for grouping. Statistical analyses were performed using SPSS 18.0 (IBM, Chicago, IL, USA). Inter-group differences were assessed for significance using the paired t test. Mean values and error bars are presented as mean ± SD and differences were considered significant if ***p < 0.001.