3D-printed engineered bacteria-laden gelatin/sodium alginate composite hydrogels for biological detection of ionizing radiation

Nuclear safety is a global growing concern,where ionizing radiation(IR)is a major injury factor resulting in serious damage to organisms.The detection of IR is usually conducted with physical dosimeters;however,biological IR detection methods are deficient.Here,a living composite hydrogel consisting of engineered bacteria and gelatin/sodium alginate was 3D-printed for the biological detection of IR.Three strains of PrecA::egfp gene circuit-containing engineered Escherichia coli were constructed with IR-dependent fluorescence,and the DH5αstrain was finally selected due to its highest radiation response and fluorescence.Engineered bacteria were loaded in a series of gelatin/sodium alginate matrix hydrogels with different rheology,3D printability and bacterial applicability.A high-gelatin-content hydrogel containing 10%gelatin/1.25%sodium alginatewas optimal.The optimal living composite hydrogelwas 3D-printedwith the special bioink,which reported significant green fluorescence underγ-ray radiation.The living composite hydrogel provides a biological strategy for the detection of environmental ionizing radiation.

The role of bacteria and its derived biomaterials in cancer radiotherapy

Bacteria-mediated anti-tumor therapy has received widespread attention due to its natural tumor-targeting ability and specific immune-activation characteristics.It has made significant progress in breaking the limitations of monotherapy and effectively eradicating tumors,especially when combined with traditional therapy,such as radiotherapy.According to their different biological characteristics,bacteria and their derivatives can not only improve the sensitivity of tumor radiotherapy but also protect normal tissues.Moreover,genetically engineered bacteria and bacteria-based biomaterials have further expanded the scope of their applications in radiotherapy.In this review,we have summarized relevant researches on the application of bacteria and its derivatives in radiotherapy in recent years,expounding that the bacteria,bacterial derivatives and bacteria-based biomaterials can not only directly enhance radiotherapy but also improve the anti-tumor effect by improving the tumor microenvironment(TME)and immune effects.Furthermore,some probiotics can also protect normal tissues and organs such as intestines from radiation via anti-inflammatory,anti-oxidation and apoptosis inhibition.In conclusion,the prospect of bacteria in radiotherapy will be very extensive,but its biological safety and mechanism need to be further evaluated and studied.

Towards overcoming obstacles of type Ⅱ photodynamic therapy:Endogenous production of light,photosensitizer,and oxygen

Conventional photodynamic therapy(PDT)approaches face challenges including limited light penetration,low uptake of photosensitizers by tumors,and lack of oxygen in tumor microenvironments.One promising solution is to internally generate light,photosensitizers,and oxygen.This can be accomplished through endogenous production,such as using bioluminescence as an endogenous light source,synthesizing genetically encodable photosensitizers in situ,and modifying cells genetically to express catalase enzymes.Furthermore,these strategies have been reinforced by the recent rapid advancements in synthetic biology.In this review,we summarize and discuss the approaches to overcome PDT obstacles by means of endogenous production of excitation light,photosensitizers,and oxygen.We envision that as synthetic biology advances,genetically engineered cells could act as precise and targeted“living factories”to produce PDT components,leading to enhanced performance of PDT.

Arsenic removal from contaminated soil via biovolatilization by genetically engineered bacteria under laboratory conditions

In Rhodopseudomonas palustris,an arsM gene,encoding bacterial and archaeal homologues of the mammalian Cyt19 As（III） S-adenosylmethionine methytransferase,was regulated by arsenicals.An expression of arsM was introduced into strains for the methylation of arsenic.When arsM was expressed in Sphingomonas desiccabilis and Bacillus idriensis,it had 10 folds increase of methyled arsenic gas compared to wild type in aqueous system.In soil system,about 2.2%–4.5% of arsenic was removed by biovolatilization during 30 days.This study demonstrated that arsenic could be removed through volatilization from the contaminated soil by bacteria which have arsM gene expressed.These results showed that it is possible to use microorganisms expressing arsM as an inexpensive,efficient strategy for arsenic bioremediation from contaminated water and soil.

Engineered bacteria as drug delivery vehicles: Principles and prospects

The development of drug delivery vehicles is in significant demand in the context of precision medicine.With the development of synthetic biology,the use of genetically engineered bacteria as drug delivery vectors has attracted more and more attention.Herein,we reviewed the research advances in bioengineered bacteria as drug carriers,with emphasis on the synthetic biology strategies for modifying these bacteria,including the targeted realization method of engineered bacteria,the designing scheme of genetic circuits,and the release pathways of therapeutic compounds.Based on this,the essential components,design principles,and health concerns of engineering bacteria as drug carriers and the development prospects in this field have been discussed.

Synthetically engineered microbes reveal interesting principles of cooperation

Cooperation is ubiquitous in biological sys- tems. However, if natural selection favors traits that confer an advantage to one individual over another, then helping others would be paradoxical. Nevertheless, cooperation persists and is critical in maintaining homeostasis in systems ranging from populations of bacteria to groupings of mammals. Developing an understanding of the dynamics and mechanisms by which cooperation operates is critical in understanding ecological and evolutionary relationships. Over the past decade, synthetic biology has emerged as a powerful tool to study social dynamics. By engineering rationally controlled and modulatable beha- vior into microbes, we have increased our overall under- standing of how cooperation enhances, or conversely constrains, populations. Furthermore, it has increased our understanding of how cooperation is maintained within populations, which may provide a useful framework to influence populations by altering cooperation. As many bacterial pathogens require cooperation to infect the host and survive, the principles developed using synthetic biology offer promise of developing novel tools and strategies to treat infections, which may reduce the use of antimicrobial agents. Overall, the use of engineered cooperative microbes has allowed the field to verify existing, and develop novel, theories that may govern cooperative behaviors at all levels of biology.