MSE 536- SP2025_Cell and Protein Interactions with Biomaterials

MSE 536: Advanced Biomaterials

• Course Focus: Cell and Protein Interactions with Biomaterials

Page 1: Overview

• Introduction to the intersection of biomaterials and cell/protein interactions.

Page 2: Receptors and Ligands

• Receptors: Protein molecules embedded in plasma membranes that bind to signaling molecules (ligands).

  • Binding leads to cellular/tissue responses.

  • Receptors are specific to ligands.

• Types of Receptors:

  1. Intracellular receptors: Located in cytoplasm or nucleus.

  2. Cell-Surface receptors: Found in plasma membrane, including:

     • Ion channel-linked receptors

     • Enzyme-linked receptors

     • G-protein-coupled receptors (GPCRs)

Page 3: Ion Channel-Linked Receptors

• Function: Open channels upon ligand binding to allow ion passage.

• Example: Neurons possess ligand-gated channels sensitive to neurotransmitters.

Page 4: Enzyme-Linked Receptors

• Structure: Receptors with intracellular domains linked to enzymes.

• Function: Some receptors act as enzymes, while others interact with enzymes.

Page 5: G-Protein-Coupled Receptors (GPCRs)

• Diverse receptors that bind various ligands.

• Example: Olfactory receptors comprise around 800 types in humans for different scent molecules.

Page 6: Cell–Environment Interactions

• Key interactions affecting cellular functions:

  • Focal adhesions: Formed by ECM molecules binding to integrins, impacting cytoskeleton and gene expression.

  • Secondary messengers: Influence gene expression in response to soluble mediators (e.g., growth factors).

• Cellular Functions Affected:

  1. Cell Viability

  2. Proliferation

  3. Differentiation

  4. Protein Synthesis

Page 7: Cell Viability

• Survival Factors: Extracellular environment changes (e.g., pH) can induce cell death.

• Cell Death Mechanisms:

  1. Necrosis: Caused by membrane permeability, leading to leakage and cellular swelling.

  2. Apoptosis: Programmed cell death with cell shrinkage and consumption of fragments.

Page 8: Cell Proliferation

• Proper environment (e.g., space) is vital for cell proliferation.

• Cell Types by Proliferation Ability:

  1. Labile cells: Continually replicate (e.g., skin cells).

  2. Permanent cells: Terminally differentiated and do not divide (e.g., neurons).

  3. Stable cells: Specific functions but can proliferate (e.g., liver cells).

Page 9: Cell Cycle Overview

• Mitosis (M phase): Cell division process.

• Interphase: Preparation phase including:

  1. G1 phase: Cell growth.

  2. S phase: DNA replication.

  3. G2 phase: Protein synthesis.

• Non-proliferating cells are in the G0 phase (quiescent).

Page 10: Mitosis Steps

1. Prophase: Nucleolus dissipates; mitotic spindles form.

2. Metaphase: Chromosomes align at spindle equator.

3. Anaphase: Chromosomes are separated.

4. Telophase: Nuclear envelope re-forms; cytokinesis begins.

Page 11: Cell Differentiation

• Stem Cells Categories:

  1. Unipotent: One differentiated cell type.

  2. Multipotent: Several cell types.

  3. Totipotent/Pluripotent: Many cell types, including embryonic stem cells.

  • Induced pluripotent stem cells (iPSCs): Genetically reprogrammed.

Page 12: Hematopoietic Stem Cell Differentiation

• Focus on blood cell production from hematopoietic stem cells.

Page 13: Mesenchymal Stem Cell (MSC) Proliferation

• Differentiation Lineages:

  • Osteogenesis, chondrogenesis, myogenesis, and more from MSCs.

Page 14: Protein Synthesis

• Key Roles: Cell communication, ECM creation/remodeling.

Page 15: Collagen Synthesis Process

• Steps: Begins with transcription (mRNA formation), followed by translation in the ER, leading to collagen triple helix formation and secretion into ECM.

Page 16: Cell Adhesion and Migration

• Impact: ECM interactions affect adhesion and migration across surfaces.

• Cellular mechanisms include membrane receptors and cytoskeleton activities.

Page 17: Cell Adhesion Models

• DLVO Theory: Interaction model for cells and surfaces based on thermodynamics and potential energy changes.

Page 18: Limitations of DLVO Model

• Considerations include steric repulsion and surface topography.

• Other models incorporate receptor-ligand interactions as chemical reactions.

Page 19: Cell Spreading and Migration Models

• Cell Spreading: Involves integrin interactions and cytoskeletal rearrangements.

• Cell Migration Steps:

  1. Membrane extension.

  2. Membrane attachment.

  3. Force generation and movement.

Page 20: Cytotoxicity

• Definition: Substances affecting cellular metabolism or protein synthesis negatively.

• Cytotoxicity testing is essential for biocompatibility assessments.

Page 21: Direct Contact Assay

• Procedure: Test material placed over cultured cells to assess cell viability near the material after exposure.

Page 22: Agar Diffusion Assay

• Cells are covered with agar to assess the effects of leachable molecules from biomaterials on viability.

Page 23: Elution (Extract) Assay

• Tests cytotoxicity of biomaterials by assessing the effects of soluble leachables on adhered cells over time.

Page 24: Cell Adhesion and Spreading Assays

• Quantitative and qualitative methods assess cell adhesion and spreading on biomaterial surfaces.

Page 25: Protein Adsorption on Biomaterial Surface

• Biological responses are influenced by the protein layer adsorbed to the biomaterial surface.

Page 26: Gibbs Free Energy (G)

• In the context of protein adsorption, considers enthalpy and entropy changes.

Page 27: System Properties Governing Protein Adsorption

• Factors affect protein adsorption such as hydrophobicity, charge redistribution, and structural rearrangements.

Page 28: Charge Impact on Protein Adsorption

• Similar charges between protein and surface lead to repulsion; opposite charges promote adsorption.

Page 29: Protein Properties Affecting Interactions

• Size, charge, hydrophobicity, and stability impact protein adsorption behavior on surfaces.

• Isoelectric point: pH equilibrium influencing protein charge for adsorption.

Page 30: Surface Properties Affecting Interactions with Proteins

• Includes surface topography, composition, hydrophobicity, and potential, each influencing protein interaction.

Page 31: Amino Acids

• Basic protein units with a central carbon, R group variation distinguishes them.

Page 32: pK Value of Amino Acids

• Higher pK values indicate more acidic characteristics; related to amino acid behavior in solutions.

Page 33: Functional Role of Amino Acids in Protein Structure

• Proline and cysteine play critical roles in determining protein folding structures via their unique properties.

Page 34: Multiple Levels of Protein Structure

• Descriptions of primary, secondary, tertiary, and quaternary structures that dictate protein function.

Page 35: Primary Structure of Proteins

• Linear order of amino acids via condensation reactions directed by DNA coding.

Page 36: Secondary Structure of Proteins

• Localized folding due to hydrogen bonding; includes helices and pleated sheets as common forms.

Page 37: Secondary Structure Variants

• Distinguished between ?-pleated sheet conformations, involving hydrogen bonding for stability.

Page 38: Tertiary Structure

• 3D arrangement driven by side chain interactions; key for protein functionality.

Page 39: Quaternary Structure

• Protein complexes formed by multiple polypeptide chains; stability can be affected by environmental conditions.

Page 40: Protein Transport to the Surface

• Hydrophobicity, charge interactions, and transport mechanisms influence protein adsorption kinetics.

Page 41: Protein Transport Dynamics

• Explains how flow and diffusion dynamics affect the transport of proteins to surfaces in biomaterials.

Page 42: Adsorption Kinetics

• High initial rates yield monolayer coverage; subsequent rearrangements and desorption dynamics.

Page 43: Reversibility of Protein Adsorption

• Initial reversible binding can precede eventual irreversible adsorption, impacting protein behavior post-adsorption.

Page 44: Desorption and Exchange

• Describes dynamic protein exchanges influenced by concentration and surface affinities.

Page 45: Vroman Effect

• Highlights how proteins of varying concentrations interact over time based on their adsorption affinities.

Page 46: Assessment Techniques

• Techniques for protein identification and quantification relate to surface interactions and adsorbate chemistry.

Page 47: Affinity Chromatography

• Utilizes hydrophobic and polar interactions for protein separation and quantification based on adsorption principles.

Page 48: Colorimetric Assay

• Quantifies specific proteins based on detectable color changes resulting from enzymatic reactions.

Page 49: Fluorescent Assay

• Measures protein presence via fluorescence changes, requiring specific instrumentation for analysis.

Page 50: Fluorescence Microscopy

• Example illustrating cell adhesion and spreading on titanium surfaces using fluorescence techniques.

Page 51: Enzyme-Linked Immunosorbent Assay (ELISA)

• Technique for identifying specific proteins using antibodies and quantifying via colorimetric changes.

Page 52: Western Blotting

• Method for protein separation and identification using gel electrophoresis and specific antibodies.