Photosymbiosis for Biomedical Applications

Abstract

Without the sustained provision of adequate levels of oxygen by the cardiovascular system, the tissues of higher animals are incapable of maintaining normal metabolic activity, and hence cannot survive. The consequence of this evolutionarily suboptimal design is that humans are dependent on cardiovascular perfusion, and therefore highly susceptible to alterations in its normal function. However, hope may be at hand. "Photosynthetic strategies," based on the recognition that photosynthesis is the source of all oxygen, offer a revolutionary and promising solution to pathologies related to tissue hypoxia. These approaches, which have been under development over the past 20 years, seek to harness photosynthetic microorganisms as a local and controllable source of oxygen to circumvent the need for blood perfusion to sustain tissue survival. To date, their applications extend from the in vitro creation of artificial human tissues to the photosynthetic maintenance of oxygen-deprived organs both in vivo and ex vivo, while their potential use in other medical approaches has just begun to be explored. This review provides an overview of the state of the art of photosynthetic technologies and its innovative applications, as well as an expert assessment of the major challenges and how they can be addressed.

Keywords: hypoxia; photosynthetic oxygen; recombinant proteins and monoclonal antibodies; regenerative medicine; tissue engineering; transgenic microalgae and cyanobacteria.

FIGURE 1

Potential applications for photosynthetic technologies. Novel approaches to organ oxygenation have shown that microorganisms with the capacity to produce oxygen when stimulated with light can improve organ functionality and survival in the absence of blood perfusion (A). Furthermore, the availability of genetic tools makes it possible to construct transgenic photosynthetic organisms that bioactivate tissue-engineered materials and confer upon them the potential to simultaneously and steadily release oxygen and functional recombinant molecules, such as growth factors (B).

FIGURE 2

Development of photosynthetic biomaterials. The combination of photosynthetic microorganisms such as cyanobacteria (A) and green algae (B–E) with biomedical devices routinely used in clinical practice, such as dermal scaffolds (B) or suture threads (C), has enabled the development of biomaterials that are capable of producing oxygen in situ. Moreover, the biocompatibility of these organisms with animal life has been demonstrated both in vitro under co-cultivation conditions with mammalian cells and in vivo in several vertebrate models like zebrafish (D) and mice (E). Scale bars represent 1 mm in (A,C,E), 1 cm in (B), and 0.2 mm in (D).