Tissue Engineering and 3D Bioprinting Lecture Notes

Flashcards based on lecture notes about tissue engineering and 3D bioprinting.

What is the definition of tissue engineering?

Understanding the principles of tissue growth and applying this to produce functional replacement tissue for clinical use.

What are the current limitations of tissue engineering?

Need more complex functionality, functional and biomechanical stability, and vascularization in laboratory-grown tissues for transplantation.

What are scaffolds used for in tissue engineering?

Structure, biodegradability, differentiate and form new tissue.

What are the challenges of scaffold-based tissue engineering approaches?

Material processability, mechanical strength, degradation rate and byproduct, scaffold morphology, and surface topography.

What is the definition of 3D bioprinting?

A layered cell printing technology using material transfer processes for patterning and assembling biologically relevant materials with a prescribed organization to accomplish biological functions.

What are the advantages of 3D bioprinting as compared to scaffold-based tissue engineering approaches?

Scalable, reproducible, mass production of engineered tissue constructs; accurate 3D positioning of different cell types; high cell density; thick tissue vascularization; and in situ printing.

List at least 4 popular bioprinting methods.

Extrusion, inkjet, solenoid valve-based, laser-based.

What are the printing principles of solenoid valve-based processes?

Bioink preparation, layer-by-layer deposition and tissue maturation.

What are the major steps for extrusion-based bioprinting process, from cell preparation to final product?

Cell preparation, bioink formulation, bioprinting, crosslinking or solidification, post-printing maturation, and evaluation.

Compare Organovo’s NovoGen MMX with Digilabs CellJet. What are the advantages and disadvantages for each of the systems?

Extrusion vs Inkjet printing pros and cons.

What are the principles of laser induced forward transfer (LIFT)?

Laser Induced Forward Transfer (LIFT) is a direct laser writing, one step process. It is a technique that uses a laser to print a small fraction of material from a thin donor layer onto a receiving substrate.

What are the key requirements of biomaterials in 3D bioprinting?

Material formability, water content, biocompatibility, suitable mechanical properties, biodegradability, biodegradation byproduct, bioactivity, and sterilization.

What is the definition of hydrogel and what hydrogel is necessary in 3D bioprinting?

Hydrogels are highly absorbent natural or synthetic polymers that are capable of cell encapsulation.

Give 3 examples of natural hydrogels and explain their basic properties.

Collagen, Gelatin, Matrigel

Give 3 examples of polysaccharide-based hydrogels

Chitosan, Alginate, Hyaluronic Acid

Give 3 examples of synthetic hydrogels and explain their basic properties

Poly(ethylene glycol), poly(vinyl alcohol), poly(2-hydroxethyl methacrylate)

Explain two key properties of hydrogel for 3D bioprinting.

Rheology and Crosslinking Mechanism.

Explain the properties of hydrogel gelation mechanics: physical and chemical crosslinking.

Physical: reversible interactions, reversible gelation, mild conditions, injectability and self-healing. Chemical: irreversible interactions, permanent gel, tunable properties, customizable functionality.

Describe biosafety levels of materials

Level 1: basic level, Level 2: moderate risk, Level 3: exotic agents with aerosol transmission, Level 4: exotic agents with life-threatening risk.

What are the major differences between immortalized cell lines and primary cells?

Immortalized cells are established, stable, and can be frozen; primary cells are cultured directly from tissue or organ.

What is the purpose of using CO2 for mammalian cell cultures?

Maintain correct pH.

Why do you need to use phosphate-buffered saline (PBS) without calcium and magnesium for rising adherent cells prior to trypsinization?

To use phosphate-buffered saline (PBS) without calcium and magnesium when rinsing adherent cells before trypsinization to help effectively detach them

Why EDTA is added in trypsin solutions?

EDTA (ethylenediaminetetraacetic acid) is added to trypsin solutions to enhance the detachment of adherent cells by chelating divalent cations like calcium (Ca²⁺) and magnesium (Mg²⁺). These ions are crucial for cell adhesion.

What is the main purpose of using DMSO for cell cryopreservation?

DMSO reduces freezing point for slower cooling rate.

What are the advantages of using 3D culture?

3D cell cultures offers: cell-cell and cell-matrix interactions, nutrient and oxygen gradients, gene expression, and drug response.

What are the two approaches in 3D cell culture models and describe their culturing processes?

Scaffold-based and Scaffold-free.

Why 3D cells cultures are important and what kinds of 3D cell cultures methods are available?

3D cell cultures offers: cell-cell and cell-matrix interactions, nutrient and oxygen gradients, gene expression, and drug response. Additive manufacturing techniques, freeze drying, micro-fabrication and electrospinning

What are the 3 imaging modalities that have been widely used in tissue modeling?

Magnetic resonance imaging (MRI), Computed tomography (CT), Optical microscopy

Describe the major steps in the manufacturing of a patient model by using additive manufacturing.

1. Image acquisition, 2. segmentation and characterization process, 3. CAD model generation

What are the major challenges of 3D bioprinting?

Regulatory issues, technical challenges, and operational challenges.

What are the four technical challenges for 3D bioprinting?

Design of 3D bioprinted constructs, bioink development, bioprinting technology, and integration with host tissue (vascularization).

What are the two operational challenges for 3D bioprinting?

Cost and development of enabling technologies.

What are the application areas that 3D bioprinting can potentially be applied to in the future?

Bone tissue engineering, vascular graft, heart tissue engineering, cartilage tissue engineering, and bioprinted tissue model for drug discovery.

What is high content screening (HCS) or high content imaging (HCI)?

HCS/ HCA (high content analysis) refers the throughput automated microscope-based assays that measures biological activity in cells after treatment with agents in multi-well plates

What is the difference between apoptosis and necrosis?

Apoptosis is a programmed cell death with caspase activation, while necrosis is rapid, uncontrolled cell death by external factors.

Name biomarkers available measuring cell viability and cytotoxicity

Cellular metabolic activity and Cell membrane integrity

What is the basic principle of ATP assays

Marker for cell viability that declines rapidly with cell necrosis or apoptosis

What is the basic principle of calcein AM and ethidium homodimer assays

Measures intracellular esterase activity or cell viability

What is the basic principle of LDH assays

Determine the cell membrane integrity.

What is the basic of determining compound incubation time with cells?

To find a duration that allows the compound to achieve its intended biological effect without causing unintended stress or degradation.