Nanotechnology: R & D challenges and opportunities for application in biotechnology

Ultra-stable zeolites—a tool for in-cell chemistry

Ultrastable zeolite particles were used as vehicles to carry low molecular bio-active substances and macromolecules as proteins into viable cells. Zeolite particles that can be used for internalisation by phagocytosis were obtained from the non-sedimenting fraction of a commercially available zeolite preparation after 1 x g sedimentation. Protein adsorbed on the zeolite surface was shown to enter the endosomal pathway after phagocytosis and could be cleaved by the endosomal proteases. As a model of a low molecular weight bio-active molecule, the inhibitor of the cellular synthesis of nitrogen oxide, N-nitro-L-arginine methyl ester (L-NAME), was used. A partial inhibition of the cellular NO production was shown after utilizing zeolites as vehicles to introduce the inhibitor into the cells. A targeting of the intra-cellular enzymes that was at least 10 times more efficient was obtained by the use of zeolites as a carrier of the inhibitor, as opposed to addition of the inhibitor to the culture medium.

Bioartificial organs in the twenty-first century: nanobiological devices

Bioartificial organs involve the design, modification, growth and maintenance of living tissues embedded in natural or synthetic scaffolds to enable them to perform complex biochemical functions, including adaptive control and the replacement of normal living tissues. Future directions in this area will lead to an abandonment of the trial-and-error implant optimization approach and a switch to the rational production of precisely formulated nanobiological devices. This will be accomplished with the help of three major thrusts: (1) use of molecularly manipulated nanostructured biomimetic materials; (2) application of microelectronic and nanoelectronic interfacing for sensing and control; and (3) application of drug delivery and medical nanosystems to induce, maintain, and replace a missing function that cannot be readily substituted with a living cell and to accelerate tissue regeneration. Biomimetics involves employment of microstructures and functional domains of organismal tissue function, correlation of processes and structures with physical and chemical processes, and use of this knowledge base to design and synthesize new materials for health applications. Nanostructured materials should involve biological materials (rather then synthetic ones) because their prefabricated structure is suitable for modular control of devices from existing materials. Nanostructured tools should encompass surface patterned molecular arrays, nanoscale synthetic scaffolding mimicking the cell-extracellular matrix microenvironment, precise positioning of molecules with specific signals to provide microheterogeneity, composites of bioinorganic and organic molecules, molecular layering (coating), and molecular and supramolecular self-assembly and self-organization (template-directed) assembly. The nanoelectronic interface includes electronic or optoelectronic biointerfaced devices based on individual cells, their aggregates and tissues, organelles, and molecules, such as enzyme-based devices, transport and ion-channel membrane proteins, and receptor-ligand structures, including nanostructured semiconductor chips and microfluidic components. Delivery nanosystems encompass both water and lipid core vehicles (for hydrophilic and lipophilic components) of various geometries: liposomes, micelles, nanoparticles, lipid shells (as imaging and contrasting agents), solid nanosuspensions, lipid nanospheres, and coated film surfaces (molecular layering), all for use in delivering drugs, proteins, cell modifiers, and genes. Nanoelectronic interface and delivery nanosystems will be used for sensing, feedback, control, and analysis of function of bioartificial organs.

Rho Chi lecture. Pharmaceutical sciences in the next millennium

Even a cursory survey of this article suggests that the pharmaceutical sciences are being rapidly transformed under the influence of both the new technologies and sciences and the economic imperatives. Of particular importance are scientific and technological advances that may greatly accelerate the critical process of discovery. The possibility of a drug discovery process built around the principles of directed diversity, self-reproduction, evolution, and self-targeting suggests a new paradigm of lead discovery, one based quite directly on the paradigms of molecular biology. Coupled with the principles of nanotechnology, we may contemplate miniature molecular machines containing directed drug factories, circulating the body and capable of self-targeting against defective cells and pathways -- the ultimate "drug delivery machine." However, science and technology are not the only factors that will transform the pharmaceutical sciences in the next century. The necessary reductions in the costs of drug discovery brought about by the rapidly increasing costs of the current drug discovery paradigms means that efforts to decrease the discovery phase and to make drug development part of drug discovery will become increasingly important. This is likely to involve increasing numbers of "alliances," as well as the creation of pharmaceutical research cells -- highly mobile and entrepreneurial groups within or outside of a pharmaceutical company that are formed to carry out specific discovery processes. Some of these will be in the biotechnology industry, but an increasing number will be in universities. The linear process from basic science to applied technology that has been the Western model since Vannevar Bush's Science: The Endless Frontier has probably never been particularly linear and, in any event, is likely to be rapidly supplanted by models where science, scientific development, and technology are more intimately linked. The pharmaceutical sciences have always been an example of use-directed basic research, but the relationships between the pharmaceutical industry, small and large, and the universities seems likely to become increasingly developed in the next century. This may serve as a significant catalyst for the continued transformation of universities into the "knowledge factories" of the 21st century. Regardless, we may expect to see major changes in the research organizational structure in the pharmaceutical sciences even as pharmaceutical companies enjoy record prosperity. And this is in anticipation of tough times to come.

Strategies for protein-based nanofabrication: Ni2+-NTA as a chemical mask to control biologically imposed symmetry

BACKGROUND

Technologies that improve control of protein orientation on surfaces or in solution, through designed molecular recognition, will expand the range of proteins that are useful for biosensors, molecular devices and biomaterials. A limitation of some proteins is their biologically imposed symmetry, which results in indistinguishable recognition surfaces. Here, we have explored methods for modifying the symmetry of an oligomeric protein that exhibits useful self-assembly properties.

RESULTS

Escherichia coli glutamine synthetase (GS) contains 24 solvent-exposed histidines on two symmetry-related surfaces. These histidines drive a metal-dependent self-assembly of GS tubes. Immobilization of GS on the affinity resin Ni2+-NTA followed by on-column modification with diethyl pyrocarbonate affords asymmetrically modified GS that self-assembles only to the extent of 'short' dimeric GS tubes, as demonstrated by electron microscopy, dynamic light scattering and atomic force microscopy. The utility of Ni2+-NTA as a chemical mask was also demonstrated for asymmetric modification of engineered cysteines adjacent to the natural histidines.

CONCLUSIONS

Current genetic methods do not provide distinguishable recognition elements on symmetry-related surfaces of biologically assembled proteins. Ni2+-NTA serves as a mask to control chemical modification in vitro of residues within symmetry-related pairs, on proteins containing functional His-tags. This strategy may be extended to modification of a wide range of amino acids with a myriad of reagents.