Nanobiomaterials in Tissue Engineering Notes

Introduction to Tissue Engineering

  • Definition:

    • An interdisciplinary field that combines engineering and life sciences.

    • Aims to understand and develop biological substitutes to restore and improve tissue functions (Langer and Vacanti, 1993).

    • Also known as "regenerative medicine" and "reparative medicine".

Key Components of Tissue Engineering

  • Scaffold Biomaterials:

    • Serve as templates for tissue growth.

    • Facilitate the organization, growth, differentiation, and functional formation of tissues.

  • Types of Cells:

    • Autologous Cells: Patient's own cells; immunologically acceptable but may have limited availability.

    • Allogeneic Cells: Cells from other humans; more readily available but may pose immunological issues.

    • Xenogeneic Cells: Cells from different species; challenging due to immunological tolerance and viral transmission risks.

    • Stem Cells: Hold the potential to differentiate into various cell types.

  • Signals:

    • Biological Signals: Growth factors, differentiation factors, angiogenic factors, and enzymes.

    • Mechanical Signals: Compressive forces and cyclic stretching.

The Central Paradigm of Tissue Engineering

  • Key stages include:

    • Cell sourcing

    • Cell expansion and manipulation

    • Cell seeding and extracellular matrix expression

    • Mechanical and molecular signaling

    • Implantation of constructs

    • Full incorporation into the host.

Characteristics of an Ideal Scaffold

  • Acts as a 3D template for tissue growth.

  • Interconnected macroporous network to support tissue ingrowth, vascularization, and nutrient delivery.

  • Bonds with host tissue with minimal scar formation.

  • Influences gene expression for effective cell differentiation and maintenance of phenotype.

  • Resorbs at the same rate tissue forms.

  • Strong enough to bear loading.

  • Cost-effective production adhering to ISO9001/FDA standards.

Scaffold Fabrication Techniques

  • Salt/Particulate Leaching:

    • Utilizes porosity and surface area to enhance scaffold effectiveness.

  • Thermal Induced Phase Separation:

    • Phase separation induced by cooling results in porous structures; various parameters affect the morphology.

  • Gas Foaming:

    • CO₂ saturation of polymers leads to bubble nucleation and scaffold porosity.

  • 3D Printing:

    • Various methods including Stereolithography, Digital Light Processing, and extrusion techniques provide customization and precision in scaffold design.

Bioreactors for Tissue Engineering

  • Purpose: To create an in vitro environment mimicking in vivo conditions for tissue formation.

  • Functions:

    • Facilitate spatially uniform cell distribution.

    • Maintain gas and nutrient concentrations.

    • Deliver physical stimuli to tissues.

Types of Bioreactors

  1. Flask (Static or Mixed)

  2. Slow Turning Lateral Vessel (STLV)

  3. High Aspect Ratio Vessel (HARV)

  4. Rotating Wall Perfused Vessel (RWPV)

  5. Perfused Column

  6. Perfused Chamber

  • Each type varies in mass transfer mechanisms, impacting efficiency.

Mechanical Stimulation in Bioreactor Systems

  • Systems can incorporate compressive and shear loading to observe mechanical properties and cell behavior in culture.

Risks Associated with Tissue Engineering

  • Contamination: Related to source materials and production processes.

  • Disease Transmission: Risks of infectious disease from cells.

  • Cell Modification Risks: Unwanted genetic alterations during cell amplification/differentiation.

  • Scaffold Interaction Risks: Unknown interactions between cells and scaffolds.

  • Toxicity Risks: From cryopreservatives and other residues; also include patient-specific responses (e.g., allergies).

Overall, understanding these aspects of tissue engineering is crucial for developing effective therapeutic strategies and mitigating associated risks in clinical applications.