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Biomedical subjects

Joel H Collier

Publications and source records attributed to Joel H Collier.

3 recordsLinked to original sources

Engineering a biospecific communication pathway between cells and electrodes.

Methods for transducing the cellular activities of mammalian cells into measurable electronic signals are important in many biotechnical applications, including biosensors, cell arrays, and other cell-based devices. This manuscript describes an approach for functionally integrating cellular activities and electrical processes in an underlying substrate. The cells are engineered with a cell-surface chimeric receptor that presents the nonmammalian enzyme cutinase. Action of this cell-surface cutinase on enzyme substrate self-assembled monolayers switches a nonelectroactive hydroxyphenyl ester to an electroactive hydroquinone, providing an electrical activity that can be identified with cyclic voltammetry. In this way, cell-surface enzymatic activity is transduced into electronic signals. The development of strategies to directly interface the activities of cells with materials will be important to enabling a broad class of hybrid microsystems that combine living and nonliving components.

Amino Acid Sequence↗

Engineering gene expression and protein synthesis by modulation of nuclear shape.

The current understanding of the relationships between cell shape, intracellular forces and signaling, nuclear shape and organization, and gene expression is in its infancy. Here we introduce a method for investigating gene-specific responses in individual cells with controlled nuclear shape and projected area. The shape of the nuclei of primary osteogenic cells were controlled on microfabricated substrata with regiospecific chemistry by confining attachment and spreading of isolated cells on adhesive islands. Gene expression and protein synthesis were altered by changing nuclear shape. Collagen I synthesis correlated directly with cell shape and nuclear shape index (NSI), where intermediate values of nuclear distension (6 < NSI < 8) promoted maximum synthesis. Osteocalcin mRNA, a bone-specific differentiation marker, was observed intracellularly by using reverse transcription in situ PCR at 4 days in cells constrained by the pattern and not detected in unconstrained cells of similar projected area, but different NSI. Our data supports the concept of gene expression and protein synthesis based on optimal distortion of the nucleus, possibly altering transcription factor affinity for DNA, transport to the nucleus, or nuclear matrix organization. The combination of microfabricated surfaces, reverse transcription in situ PCR, and NSI measurement is an excellent system to study how transcription factors, the nuclear matrix, and the cytoskeleton interact to control gene expression and may be useful for studying a wide variety of other cell shape/gene expression relationships.

Active Transport, Cell Nucleus↗

Enzymatic modification of self-assembled peptide structures with tissue transglutaminase.

A de novo peptide that self-assembles into fibrillar structures and serves as a substrate for the cross-linking enzyme tissue transglutaminase was developed (Ac-QQKFQFQFEQQ-Am). Congo red staining, circular dichroism, and FTIR spectroscopy showed that this 11-amino acid peptide produced predominantly beta-sheet structures. TEM with negative staining and quick-freeze deep etch (QFDE) TEM showed that the peptide structures were composed of a highly entangled fibrillar network. These beta-sheet fibrillar nanostructures were then covalently coupled to pendant amine-containing biomolecules via tissue transglutaminase. MALDI-TOF mass spectrometry and HPLC were utilized to monitor the extent of the transglutaminase modification of the peptide, showing that as many as five glutamines in the peptide were reactive via transglutaminase for covalent conjugation. This strategy, based on the post-assembly modification of a self-assembling peptide, has potential applications for tailoring supramolecular structures for drug delivery, tissue engineering, or other biomedical applications.

Amino Acid Sequence↗