What Are Biological Materials?

Biological materials are the molecular and supramolecular substances produced by living organisms that provide structural support, chemical function, or energy storage. They include proteins, nucleic acids, polysaccharides, lipids, and the composite materials formed when these molecules are assembled into larger structures such as cell walls, extracellular matrix, bone, and cartilage. The study of biological materials draws from biochemistry, materials science, and biomedical engineering, with the goal of understanding the relationships between molecular composition, hierarchical structure, and macroscopic mechanical or chemical properties.

Biological materials are distinguished from synthetic materials by their formation through self-assembly and enzymatic synthesis under mild aqueous conditions, their capacity for self-repair, and their degradability by biological enzymes. These properties make them attractive models for the design of engineered materials and direct substrates for biomedical applications.

Biological Cells and Structural Biomolecules

Cells are the primary producers of biological materials, secreting proteins and polysaccharides that form the extracellular matrix surrounding them. Collagen, the most abundant protein in the human body, self-assembles into fibrils with tensile strengths comparable to steel wire for their cross-sectional area. Elastin provides recoil in arterial walls and lung tissue. Chitin, a polysaccharide, forms the structural exoskeleton of arthropods and the cell walls of fungi. Lipids, including phospholipids and neutral fats (triglycerides), constitute the bilayer membranes of cells and serve as energy depots; research on biomimetic lipid membranes documents the physical properties and engineering applications of these amphiphilic assemblies. The mechanical behavior of biological materials at the cellular and tissue level is shaped by how these molecular components are organized and cross-linked.

Biomedical Materials

Biomedical materials are natural or engineered materials designed for contact with biological tissue, whether for implantation, drug delivery, or diagnostic purposes. Naturally derived biomedical materials include collagen gels, hyaluronic acid scaffolds, fibrin matrices, and decellularized extracellular matrix, all of which offer biocompatibility and cell-instructive properties that fully synthetic materials struggle to replicate. Research on biomimetic materials for tissue engineering published in PMC demonstrates that mimicking the composition and nanoscale architecture of native extracellular matrix significantly improves cell attachment, proliferation, and differentiation in engineered constructs. Key performance criteria for biomedical materials include mechanical matching with surrounding tissue, controlled degradation rates, and minimal inflammatory response.

Tissue Engineering Applications

Tissue engineering combines living cells with biological or synthetic scaffold materials to construct functional tissue substitutes for repair or replacement of damaged organs. The scaffold provides a three-dimensional template that cells can colonize and remodel, and its material properties, including stiffness, porosity, and surface chemistry, guide cell behavior. PMC research on biomaterials for tissue engineering surveys the spectrum of natural and synthetic polymers used in tissue engineering, comparing their degradation kinetics, mechanical properties, and integration with host tissue. Bioreactors apply mechanical stimulation to maturing constructs to drive the alignment and organization of collagen fibers, reproducing the anisotropic structure of tendons and cardiac muscle.

Applications

Biological materials have applications in a wide range of fields, including:

• Orthopedic and dental implants, using bone-mineral-mimicking hydroxyapatite composites
• Cardiovascular repair, including bioprosthetic heart valves and vascular grafts
• Wound healing and skin substitutes using collagen-based dressings
• Drug delivery systems based on lipid nanoparticles and protein carriers
• Soft robotics and biohybrid actuators drawing on muscle tissue mechanics