# WIA-BIO-006 — Phase 1: Data Format > Tissue-engineering canonical Phase 1: scaffold + bioink + architecture + cell-source + QC envelopes. # WIA-BIO-006: Tissue Engineering Specification v1.0 > **Standard ID:** WIA-BIO-006 > **Version:** 1.0.0 > **Published:** 2025-12-26 > **Status:** Active > **Authors:** WIA Biomedical Engineering Research Group --- ## Table of Contents 1. [Introduction](#1-introduction) 2. [Scaffold Materials and Design](#2-scaffold-materials-and-design) 3. [3D Bioprinting Protocols](#3-3d-bioprinting-protocols) 4. [Bioreactor Systems](#4-bioreactor-systems) 5. [Vascularization Strategies](#5-vascularization-strategies) 6. [Cell Culture and Seeding](#6-cell-culture-and-seeding) 7. [Quality Testing Standards](#7-quality-testing-standards) 8. [Regulatory Requirements](#8-regulatory-requirements) 9. [Implementation Guidelines](#9-implementation-guidelines) 10. [References](#10-references) --- ## 1. Introduction ### 1.1 Purpose This specification defines the comprehensive framework for tissue engineering, covering scaffold design, biofabrication, cell culture, and quality assurance for regenerative medicine applications. ### 1.2 Scope The standard covers: - Natural, synthetic, and hybrid biomaterial scaffolds - 3D bioprinting techniques and protocols - Bioreactor design and operation - Vascularization and perfusion strategies - Quality control and regulatory compliance ### 1.3 Philosophy **弘益人間 (Benefit All Humanity)** - This standard aims to advance tissue engineering to restore health, save lives, and improve quality of life through regenerative medicine accessible to all. ### 1.4 Terminology - **Scaffold**: Three-dimensional structure that supports cell attachment and tissue formation - **Bioprinting**: Additive manufacturing process using living cells - **Bioreactor**: Device that provides controlled environment for tissue culture - **ECM**: Extracellular matrix - natural scaffold produced by cells - **Decellularization**: Process of removing cells while preserving ECM structure --- ## 2. Scaffold Materials and Design ### 2.1 Natural Biomaterials #### 2.1.1 Collagen **Properties**: ``` Young's Modulus: 1-10 MPa Degradation: 2-8 weeks Porosity: 70-95% Cell Adhesion: Excellent (RGD domains) ``` **Applications**: Skin, bone, cartilage, vascular grafts **Preparation**: 1. Extract from animal sources (bovine, porcine) 2. Purify via salt precipitation 3. Neutralize to pH 7.4 4. Cross-link if needed (EDC, genipin) #### 2.1.2 Gelatin **Properties**: ``` Young's Modulus: 0.1-1 MPa Degradation: 1-4 weeks Gelation Temperature: 20-30°C Biocompatibility: Excellent ``` **Advantages**: - Low immunogenicity - Thermoresponsive gelation - Cost-effective - Easy to process #### 2.1.3 Chitosan **Properties**: ``` Young's Modulus: 1-2 GPa Degradation: 4-12 weeks pH-responsive: Yes Antimicrobial: Yes ``` **Processing**: - Dissolve in acidic solution (pH 5-6) - Freeze-dry for porous structures - Can be blended with other polymers #### 2.1.4 Alginate **Properties**: ``` Ionic cross-linking: Ca²⁺, Ba²⁺ Gelation: Instantaneous Young's Modulus: 10-100 kPa Biocompatibility: Good ``` ### 2.2 Synthetic Biomaterials #### 2.2.1 Polycaprolactone (PCL) **Properties**: ``` Young's Modulus: 200-400 MPa Degradation: 6-24 months Melting Point: 60°C Hydrophobicity: High ``` **Advantages**: - FDA approved - Excellent mechanical properties - Slow degradation (matches bone healing) - Easy to process (electrospinning, 3D printing) #### 2.2.2 Polylactic Acid (PLA) **Properties**: ``` Young's Modulus: 2-4 GPa Degradation: 6-12 months Glass Transition: 60-65°C Crystallinity: 37% ``` **Applications**: Bone, cartilage, temporary implants #### 2.2.3 Polyglycolic Acid (PGA) **Properties**: ``` Young's Modulus: 7 GPa Degradation: 2-4 weeks Highly crystalline: 45-55% Water soluble: Yes ``` **Uses**: Fast-degrading applications, sutures ### 2.3 Hybrid Scaffolds #### 2.3.1 PCL-Collagen Composite ``` Composition: 70% PCL + 30% Collagen Young's Modulus: 50-150 MPa Porosity: 65-80% Degradation: 3-6 months ``` **Benefits**: - Combines mechanical strength (PCL) with bioactivity (collagen) - Tunable degradation rate - Enhanced cell adhesion #### 2.3.2 Gelatin-Alginate Blend ``` Ratio: 1:1 to 3:1 (gelatin:alginate) Gelation: Dual (thermal + ionic) Mechanical Strength: 10-50 kPa Injectable: Yes ``` ### 2.4 Scaffold Architecture #### 2.4.1 Porosity Design ``` P = (1 - ρ_apparent / ρ_material) × 100% ``` Where: - `P` = Porosity (%) - `ρ_apparent` = Apparent density (g/cm³) - `ρ_material` = Material density (g/cm³) **Recommended ranges**: - Bone: 60-80% - Cartilage: 70-85% - Skin: 80-95% - Liver: 85-90% #### 2.4.2 Pore Size ``` d_pore = (6 × V_void / S_pore) ``` Where: - `d_pore` = Average pore diameter (μm) - `V_void` = Void volume (mm³) - `S_pore` = Pore surface area (mm²) **Optimal pore sizes**: - Osteoblasts: 100-400 μm - Fibroblasts: 50-150 μm - Endothelial cells: 30-100 μm - Hepatocytes: 20-50 μm #### 2.4.3 Interconnectivity Minimum interconnectivity: **90%** ``` I = (N_connected / N_total) × 100% ``` Where: - `I` = Interconnectivity (%) - `N_connected` = Connected pores - `N_total` = Total pores ### 2.5 Mechanical Properties #### 2.5.1 Compression Testing ``` σ = F / A₀ ε = ΔL / L₀ E = σ / ε ``` Where: - `σ` = Compressive stress (Pa) - `F` = Applied force (N) - `A₀` = Initial cross-sectional area (m²) - `ε` = Strain (dimensionless) - `ΔL` = Change in length (m) - `L₀` = Initial length (m) - `E` = Young's modulus (Pa) #### 2.5.2 Tissue-Specific Requirements | Tissue | Young's Modulus | Ultimate Strength | Strain at Failure | |--------|----------------|-------------------|-------------------| | Bone | 10-20 GPa | 100-200 MPa | 1-3% | | Cartilage | 0.5-2 MPa | 5-25 MPa | 10-20% | | Skin | 0.1-2 MPa | 1-20 MPa | 30-70% | | Liver | 0.5-1 kPa | 1-5 kPa | 20-40% | | Cardiac | 10-50 kPa | 10-100 kPa | 15-30% | --- --- ## A.1 Scaffold-record envelope The Phase 1 envelope groups scaffold records by material family (natural — collagen, gelatin, chitosan, alginate, fibrin, hyaluronic acid, silk fibroin; synthetic — PCL, PLA, PGA, PLGA, PEG, polyurethane; hybrid composites; decellularized extracellular matrix) with the canonical fields: chemical formula or polymer ratio, mean Young's modulus in Pa, ultimate strength, strain at failure, porosity in %, mean pore diameter in micrometres, interconnectivity in %, degradation half-life, and the cross-link chemistry (EDC, genipin, UV-initiated photocrosslinking, ionic, thermal). Material data follows the reporting conventions of ASTM F2150 (characterisation of biomaterial scaffolds) and ISO 13314 (compression test for porous metals — applied analogously for polymeric scaffolds). ## A.2 Bioink-formulation envelope A bioink record MUST list polymer base, polymer concentration in % (w/v), cross-linker (Ca2+, light at 365/405 nm, temperature, enzymatic), cell type, cell density in cells/mL, growth-factor cocktail (VEGF, BMP, FGF, TGF-beta, IGF-1) in ng/mL, viscosity at the print shear rate in mPa·s, storage modulus G' in Pa, loss modulus G'' in Pa, and the rheological profile (shear-thinning index n, yield stress). Bioinks intended for FDA submission MUST cross-reference the Phase 4 §A.3 regulatory envelope so downstream consumers can see the regulatory pathway from one record. ## A.3 Architecture descriptor The architecture descriptor enumerates pore-network topology (gyroid, Schwarz P, Schoen IWP, octet truss, stochastic foam, hierarchical micro/macro), pore-size distribution (mean, standard deviation, D10/D50/D90 percentiles), surface-area-to-volume ratio, fibre diameter for electrospun scaffolds, fibre alignment (anisotropy index), and the mechanical anisotropy axes. Tissue-specific architectures cross-reference the target-tissue envelope at Phase 3 §A.5 so downstream consumers can verify the architecture-to-tissue match. ## A.4 Cell-source descriptor Every cell-source envelope carries: source category (primary, established cell line, stem cell — ESC/MSC/iPSC/HSC), donor metadata (ID, age, sex, ethnicity where consented, lot number), passage number, viability at thaw in %, sterility status (mycoplasma-free per USP <63>; endotoxin per USP <85> at < 0.5 EU/mL), karyotype (for stem cells), differentiation marker panel, and the chain-of-custody hash that ties the cells to the contributing institution's signing key. ## A.5 Quality-test descriptor Quality-test descriptors carry test category (sterility per USP <71>, endotoxin per USP <85>, cytotoxicity per ISO 10993-5, mechanical per ASTM F2150, biocompatibility per ISO 10993-6 implantation, immunogenicity), measurement method, instrument identifier, calibration record reference, raw measurement payload (or link to the data store), processed result, pass/fail flag against the standard's acceptance criteria, and the analyst signature. Reports MUST cite the controlling ISO/ASTM/USP document and MUST include a measurement-uncertainty budget per ISO/IEC Guide 98-3 (GUM). --- ## Z.1 Glossary, conformance, governance A companion glossary at `https://wiastandards.com/tissue-engineering/glossary/` expands every term used throughout this Phase. The conformance test suite at `https://github.com/WIA-Official/wia-tissue-engineering-conformance` walks every endpoint and protocol exchange. The reference container at `wia/tissue-engineering-host:1.0.0` ships every tissue-engineering envelope and endpoint with mock data so integrators can exercise the contract before wiring real backends. The companion CLI at `cli/tissue-engineering.sh` ships sample envelope generators with no dependencies beyond `jq` and POSIX shell. ## Z.2 Cross-standard composition (recap) This Phase composes with WIA-OMNI-API for credential storage, WIA-AIR-SHIELD for runtime trust list, WIA-SOCIAL Phase 3 §5 for federation handshake, WIA-INTENT for workload intent declaration, and (where personal data is processed) WIA Secure Enclave for sealed-data envelopes. The composition lets one host running multiple WIA family standards reuse one identity, one signing key chain, and one audit transport rather than maintaining N parallel implementations. ## Z.3 Implementation runbook A first implementation typically follows: stand up the reference container; run the conformance suite against it end-to-end; replace the mock backend with a real backend one endpoint at a time; wire audit-log replication out to the operations sink; onboard a single trusted peer for federation; expand to multiple peers; promote to production with the warning-envelope subscription enabled and the runbook in §Z.5 followed. ## Z.4 Backwards-compatibility promise Within the 1.x line, every Phase 1 envelope shape, every Phase 2 endpoint, and every Phase 3 protocol exchange MUST remain reachable and MUST continue to honour the documented status codes and content shapes. Hosts MAY add optional fields and new envelopes; hosts MUST NOT remove existing ones. Breaking changes ride a major version bump with a 12-month deprecation window per IETF RFC 8594 and 9745 and require a two-thirds Committee vote. ## Z.5 Closing implementer note This Phase fits inside the WIA Standards four-Phase architecture: Phase 1 envelopes are the wire-format contract; Phase 2 surfaces them through HTTPS; Phase 3 wraps them in protocol exchanges that cross trust boundaries; Phase 4 integrates with the broader ecosystem. Tissue-engineering deployments that follow this layering inherit the per-Phase conformance gates and the cross-standard composition behaviour described in Z.2. 弘益人間 — Benefit All Humanity.