Study On The Applications Of Bacillus Spores In Organic Synthesis And As Vaccine Adjuvants

Bacillus spores were a class of important biomaterial with long history,which were widely used in the fields including biosensor,biocatalysis,biomedicine,bioremediation,and biomineralization.This article is aiming at(1)developing a sustainable,green and efficient spore-based catalytic system;(2)constructing a spore@zeolitic imidazolate framework-8(ZIF-8)vaccine platform with higher antigen loading capacity and enhanced immunological stimulating ability.The conclusions of this article are described in detail as follows:1)The spores were used to catalyze the cross-coupling of 1,2-phenylenediamine and2-aminophenol to 2,3-diaminophenazine and 2-amino-3H-phenoxazin-3-one with the yields of 70% and 85%,respectively.The spores coupled with intermedium 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO)were applied to catalyze the oxidation of benzyl alcohol,4-methoxyl alcohol,and 3,4-dimethoxyl alcohol to benzaldehyde,4-methoxybenzaldehyde,and 3,4-dimethoxybenzaldehyde with the yields of 91%,95%,and96%,respectively,as well as the selectivity over 98%.At last,it was confirmed that the mechanism of spore catalyzed oxidation was that their surface was rich of coat protein A(Cot A)laccase,which was also capable of oxidizing TEMPO to a strong intermediate oxidant oxo-TEMPO.2)The spore@OVA@ZIF-8(SOZ)microspheres prepared by one pot method using ovalbumin(OVA)as model antigen were utilized as vaccine carriers.In vitro dendritic cells(DCs)experiments indicated that the antigen amount delivered by spore@OVA@ZIF-8was 3.4 times that delivered by sole ZIF-8 or spores,and 1.7 times that by aluminum adjuvant(Alum);about 43% of the antigen delivered by SOZ escaped from the lysosomes;ZIF-8 shell on the surface of spores could significantly improve their ability to stimulate DCs to mature and secret cytokines.In vivo mice vaccination showed that the antibody titer of SOZ immunized mice with was 18 times that of OVA@ZIF-8(OZ)group,3 times that of spore group,and 2 times that of Alum group;the percentage of T cells in the splenocytes from SOZ group was higher,and the ability to proliferate as well as to produce cytokines was significantly enhanced;the antigen could be stored longer at the injection site under the protection of ZIF-8,which was comparable to that protected by Alum.Finally,the observation of paraffin tissue sections suggested that the SOZ vaccine formulation was relatively biologically safe.In conclusion,the constructed spore-based catalytic systems could efficiently and selectively catalyze the oxidation of series of aromatic compounds for organic synthesis.They showed several advantages over free laccases,such as low cost,no need for complex preparation,high stability of activity,and capacity to be reused.The spore@ZIF-8 vaccine platform exhibited multiple immune enhancement mechanisms,which could effectively protect the antigens as well as help them escape from the lysosomes,thus significantly enhancing the humoral and cellular responses.This platform had some merits including easy preparation,cost-effective,long life,convenience of transportation and storage,and no need for the cold chain.Therefore,Bacillus spores are a kind of green,safe and effective biomaterial with great potentials in organic synthesis and as vaccine adjuvants.