Lecture_2-4 Natural Polymers and Applications_2024_MM

Natural Biopolymers, Functions and Applications

Overview

• Presented by Prof. MAK Wing Cheung Martin, CUHKBME BMEG3430.

Content Breakdown

• Types of Natural Polymers and Their Biological Functions

• Biopolymers within Extracellular Matrix (ECM)

• Proteins and Glycoproteins

• Proteoglycans and Glycosaminoglycans

• Polysaccharides

• How to Obtain Natural Biopolymers

• Applications of Natural Biopolymers

Types of Biopolymers

Proteins and Glycoproteins

• Glycoproteins: proteins with oligosaccharide chains

  • Examples:

    • Collagen

    • Elastin

    • Fibronectin

    • Albumin

    • Globulin

    • Fibrinogen

    • Silk

    • Proteoglycans

    • Additional proteins

Polysaccharides

• Glycosaminoglycans (GAGs)

  • Hyaluronic Acid (HA), Heparin, Alginate, Chitosan, Cellulose

  • Various biological roles and applications.

Advantages and Limitations of Natural Biopolymers

Advantages

• Sourced from natural resources and biosynthetic processes

• Possess active biological functions (Bioactive biomaterials)

• Exhibits biocompatibility and biodegradability.

Limitations

• Batch-to-batch variability from natural extraction

• Potential for easy degradation and loss of active functions

• Ethical concerns regarding extraction from human sources

Biopolymers in Extracellular Matrix (ECM)

ECM Characteristics

• Comprised of secreted products from resident cells in tissues and organs

• Contains a mixture of structural and functional biopolymers organized in a tissue-specific three-dimensional structure.

Functions of ECM

• Provides mechanical support to cells and tissues

• Influences vital cell activities: adhesion, migration, development, differentiation

• Coordinates cellular functions through signaling with adhesion receptors

• Serves as a reservoir for extracellular signaling molecules.

ECM Composition

Key Components

• Proteins

  • Primarily structural proteins like Collagen and Elastin

• Glycoproteins

  • Specialized proteins like Fibronectin and Laminin

• Proteoglycans

  • Composed of complex proteins with long chains of polysaccharides (e.g., GAGs)

Proteins and Glycoproteins

Collagen

• Main structural protein with a triple helix structure

• Abundant, comprising 25-35% of total body protein

• Major part (over 90%) of ECs dry weight, over 20 types, with prominent types being:

  • Type I: Skin, tendon, bone

  • Type II: Cartilage

  • Type III: Blood vessels

• Collagen I is the major component

Elastin

• Forms an interconnected diffuse fiber network

• Provides elasticity to connective tissue through hydrophobic regions that form coiled structures, enabling recoil after stretching.

Fibronectin

• Multi-binding domain adhesive glycoprotein

• Important for connections between the intra- and extracellular environments

• Critical for cell adhesion, spreading, and migration.

Albumin

• Most abundant plasma protein in blood

• Synthesized by hepatocytes; maintains osmotic pressure and transports hormones, ions, and medications.

Globulins and Immunoglobulins

• Synthesized by hepatocytes

• Immunoglobulins produced by lymphocytes; key role in immune response.

Fibrinogen

• Plasma glycoprotein involved in clot formation

• Converted to fibrin by thrombin during injury.

Silk Fibroin

• Derived from silkworm larvae and spider webs

• Exhibits antibacterial properties useful in wound healing and tissue engineering.

Proteoglycans and Glycosaminoglycans

Proteoglycans

• Complexes of glycosaminoglycan (GAG) and proteins

• Formed by hyaluronic acid backbone + core protein + GAG

• Important for tissue hydration and cushioning.

Glycosaminoglycans (GAGs)

• Negatively charged polysaccharides that influence various cellular processes and are integral to proteoglycans.

Types of GAGs and Locations

Key GAGs

• Hyaluronic Acid: Joints, cartilage

• Chondroitin Sulfate: Cartilage, tendon

• Heparin: Mast cells

• Dermatan Sulfate: Skin, blood vessels

• Keratan Sulfate: Cartilage, cornea

Applications of Natural Biopolymers

Biopolymer Extraction Techniques

• Extracted from non-mammalian sources, purification, decellularization, and recombination

  • Advantages and limitations of each method vary.

• Heparin used for blood-contacting surfaces and applications in tissue engineering.

• Essential for cell attachment and growth in regenerative applications.

Summary

• Discussed the advantages and limitations of natural biopolymers, gave examples of proteins/glycoproteins, proteoglycans, GAGs, polysaccharides, and methods for obtaining biopolymers, especially in tissue engineering applications.

Q&A

• Contact: Prof. Martin Wing Cheng Mak, Email: wing.cheung.mak@cuhk.edu.hk