title: Structural and functional features of self-assembling protein nanoparticles produced in endotoxin-free Escherichia coli.
abstract: BACKGROUND
  Production of recombinant drugs in process-friendly endotoxin-free bacterial factories targets to a lessened complexity of the purification process combined with minimized biological hazards during product application. The development of nanostructured recombinant materials in innovative nanomedical activities expands such a need beyond plain functional polypeptides to complex protein assemblies. While Escherichia coli has been recently modified for the production of endotoxin-free proteins, no data has been so far recorded regarding how the system performs in the fabrication of smart nanostructured materials.
  
  
  RESULTS
  We have here explored the nanoarchitecture and in vitro and in vivo functionalities of CXCR4-targeted, self-assembling protein nanoparticles intended for intracellular delivery of drugs and imaging agents in colorectal cancer. Interestingly, endotoxin-free materials exhibit a distinguishable architecture and altered size and target cell penetrability than counterparts produced in conventional E. coli strains. These variant nanoparticles show an eventual proper biodistribution and highly specific and exclusive accumulation in tumor upon administration in colorectal cancer mice models, indicating a convenient display and function of the tumor homing peptides and high particle stability under physiological conditions.
  
  
  CONCLUSIONS
  The observations made here support the emerging endotoxin-free E. coli system as a robust protein material producer but are also indicative of a particular conformational status and organization of either building blocks or oligomers. This appears to be promoted by multifactorial stress-inducing conditions upon engineering of the E. coli cell envelope, which impacts on the protein quality control of the cell factory.
authors.affiliation: Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.
authors.forename: Fabián
authors.initials: F
authors.lastname: Rueda
authors.affiliation: CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|Biomedical Research Institute Sant Pau (IIB-SantPau) and Josep Carreras Leukemia Research Institute, Hospital de la Santa Creu i Sant Pau, 08025, Barcelona, Spain.
authors.forename: María Virtudes
authors.initials: MV
authors.lastname: Céspedes
authors.affiliation: Servei de Microscòpia, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Sánchez-Chardi
authors.affiliation: Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|Cibbim-Nanomedicine, Hospital Vall d'Hebron, Passeig de la Vall d'Hebron, 119-129, 08035, Barcelona, Spain.
authors.forename: Joaquin
authors.initials: J
authors.lastname: Seras-Franzoso
authors.affiliation: Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.
authors.forename: Mireia
authors.initials: M
authors.lastname: Pesarrodona
authors.affiliation: Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.
authors.forename: Neus
authors.initials: N
authors.lastname: Ferrer-Miralles
authors.affiliation: Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Vázquez
authors.affiliation: Leibniz University of Hannover, Technical Chemistry & Life Science, Hannover, Germany.|Helmholtz Centre for Infection Research, Inhoffenstraße 7, Brunswick, Germany.
authors.forename: Ursula
authors.initials: U
authors.lastname: Rinas
authors.affiliation: CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|Biomedical Research Institute Sant Pau (IIB-SantPau) and Josep Carreras Leukemia Research Institute, Hospital de la Santa Creu i Sant Pau, 08025, Barcelona, Spain.
authors.forename: Ugutz
authors.initials: U
authors.lastname: Unzueta
authors.affiliation: Division of Structural Biochemistry, Priority Area Asthma and Allergy, Research Center Borstel, Airway Research Center North (ARCN), Member of the German Center for Lung Research (DZL), 23845, Borstel, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Mamat
authors.affiliation: CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|Biomedical Research Institute Sant Pau (IIB-SantPau) and Josep Carreras Leukemia Research Institute, Hospital de la Santa Creu i Sant Pau, 08025, Barcelona, Spain.
authors.forename: Ramón
authors.initials: R
authors.lastname: Mangues
authors.affiliation: Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.|Department of Ruminant Production, Institut de Recerca i Tecnologia Agroalimentàries (IRTA), Torre Marimon, Caldes de Montbui, 08140, Barcelona, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: García-Fruitós
authors.affiliation: Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain. antoni.villaverde@uab.cat.|Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain. antoni.villaverde@uab.cat.|CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain. antoni.villaverde@uab.cat.
authors.forename: Antonio
authors.initials: A
authors.lastname: Villaverde
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D016503:Drug Delivery Systems / Q000379:methods; D004926:Escherichia coli / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D053758:Nanoparticles / Q000737:chemistry / Q000378:metabolism; D010316:Particle Size; D058105:Polymerization; D015202:Protein Engineering / Q000379:methods; D055503:Protein Multimerization; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D013329:Structure-Activity Relationship
chemical_list: D011506:Proteins; D011994:Recombinant Proteins
keywords: Biodistribution; Biomaterials; E. coli; Endotoxin-free strains; Nanomedicine; Nanoparticles; Protein engineering; Recombinant proteins