# WIA-BIO-006 — Phase 2: API Interface > Tissue-engineering canonical Phase 2: API surface (scaffold-record + bioink + construct + bioreactor telemetry). # 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) --- ## 6. Cell Culture and Seeding ### 6.1 Cell Sources #### 6.1.1 Primary Cells **Advantages**: - Native phenotype - Tissue-specific function **Limitations**: - Limited expansion - Donor variability - Ethical considerations #### 6.1.2 Stem Cells **Types**: - **Embryonic stem cells (ESCs)**: Pluripotent, ethical concerns - **Mesenchymal stem cells (MSCs)**: Multipotent, bone marrow/adipose - **Induced pluripotent stem cells (iPSCs)**: Patient-specific, reprogrammed **Differentiation protocols**: Tissue-specific growth factors, mechanical cues #### 6.1.3 Cell Lines **Examples**: - NIH 3T3 (fibroblasts) - HepG2 (hepatocytes) - MC3T3 (osteoblasts) **Advantages**: - Unlimited supply - Reproducibility - Cost-effective ### 6.2 Cell Seeding Methods #### 6.2.1 Static Seeding **Protocol**: 1. Prepare cell suspension (10⁶-10⁷ cells/mL) 2. Pipette onto scaffold 3. Incubate 2-4 hours (attachment) 4. Add culture medium 5. Flip scaffold (optional, for uniform seeding) **Efficiency**: 20-50% #### 6.2.2 Dynamic Seeding **Spinner flask method**: 1. Place scaffold in spinner flask 2. Add cell suspension 3. Rotate at 50 rpm for 4-8 hours 4. Transfer to static culture **Efficiency**: 40-70% #### 6.2.3 Vacuum Seeding **Protocol**: 1. Place scaffold in vacuum chamber 2. Add cell suspension 3. Apply vacuum (50-100 kPa, 5-10 min) 4. Release vacuum (cells drawn into pores) **Efficiency**: 60-90% #### 6.2.4 Centrifugal Seeding **Parameters**: ``` RCF = 1.12 × r × (RPM/1000)² ``` Where: - `RCF` = Relative centrifugal force (×g) - `r` = Radius (mm) - `RPM` = Revolutions per minute **Protocol**: - Centrifuge at 100-500 ×g for 5-10 min - Efficiency: 70-95% ### 6.3 Cell Density Optimization ``` D_optimal = f(tissue type, scaffold porosity, culture duration) ``` **Guidelines**: - **Bone**: 5 × 10⁶ - 2 × 10⁷ cells/cm³ - **Cartilage**: 2 × 10⁷ - 6 × 10⁷ cells/cm³ - **Skin**: 1 × 10⁶ - 5 × 10⁶ cells/cm² - **Liver**: 5 × 10⁷ - 2 × 10⁸ cells/cm³ --- ## 9. Implementation Guidelines ### 9.1 Required Components Any WIA-BIO-006 compliant system must include: 1. **Scaffold Designer**: CAD integration, material selection 2. **Bioreactor Controller**: Parameter monitoring and control 3. **Quality Validator**: Automated testing protocols 4. **Bioprinting Module**: Toolpath generation, cell handling 5. **Documentation System**: GMP-compliant record keeping ### 9.2 API Interface #### 9.2.1 Design Scaffold ```typescript interface ScaffoldRequest { tissueType: string; material: BiomaterialType; porosity: number; // percentage poreSize: number; // micrometers dimensions: { length: number; // mm width: number; // mm height: number; // mm }; } interface ScaffoldResponse { id: string; volume: number; // mm³ surfaceArea: number; // mm² cellCapacity: number; // cells mechanicalProperties: MechanicalProperties; fabricationMethod: string; } ``` #### 9.2.2 Optimize Culture ```typescript interface CultureRequest { tissueConstruct: TissueConstruct; cellType: string; duration: number; // days bioreactorType: string; } interface CultureResponse { flowRate: number; // mL/min oxygenLevel: number; // percentage temperature: number; // celsius shearStress: number; // dyne/cm² predictedMaturation: number; // days qualityScore: number; // 0-1 } ``` ### 9.3 Data Formats #### 9.3.1 Scaffold Configuration ```json { "scaffold_id": "SCF-2025-001", "material": { "type": "pcl-collagen", "ratio": "70:30", "crosslinking": "EDC" }, "architecture": { "porosity": 75, "pore_size": 200, "interconnectivity": 95 }, "dimensions": { "length": 10, "width": 10, "height": 3, "unit": "mm" }, "mechanical": { "youngs_modulus": 50, "ultimate_strength": 5, "unit": "MPa" } } ``` ### 9.4 Error Handling Standard error codes: | Code | Meaning | Action | |------|---------|--------| | B001 | Insufficient porosity | Increase pore size | | B002 | Cell viability too low | Check seeding protocol | | B003 | Mechanical failure | Strengthen scaffold | | B004 | Contamination detected | Re-sterilize | | B005 | Poor vascularization | Add growth factors | | B006 | Biocompatibility issue | Change material | --- --- ## A.1 Endpoint reference ```http POST /tissue-engineering/v1/scaffolds # register scaffold record GET /tissue-engineering/v1/scaffolds/{id} # fetch scaffold record POST /tissue-engineering/v1/bioinks # register bioink formulation POST /tissue-engineering/v1/constructs # tissue construct lifecycle GET /tissue-engineering/v1/constructs/{id}/quality # latest QC results WS /tissue-engineering/v1/bioreactor/stream # bioreactor telemetry POST /tissue-engineering/v1/qc-results # contribute QC measurement ``` Every endpoint follows the discovery convention at `/.well-known/wia-tissue-engineering`. ## A.2 Scaffold-record API `POST /scaffolds` accepts the Phase 1 §A.1 envelope and returns a stable `scaffoldId`. Subsequent characterisation reports reference the `scaffoldId`. Updates to the canonical record produce a new version with the prior version preserved in the version history. Read endpoints expose the Bayesian posterior over Young's modulus and ultimate strength so downstream simulators can propagate measurement uncertainty into structural predictions. ## A.3 Bioink and construct API `POST /bioinks` registers a bioink formulation with the parameters listed in Phase 1 §A.2. Constructs intended for clinical use MUST cross-reference both the scaffold record and the bioink record. The `POST /constructs` endpoint creates a tissue-construct lifecycle record, tracking print parameters (G-code reference, layer height, print speed, pressure), cross-linking schedule, bioreactor culture history, and the QC milestone log. Read endpoints expose the live `viability/maturity` history at the construct level so SDKs can plot drift over fabrication batches. ## A.4 Quality-control and biocompatibility API `POST /qc-results` registers a quality-control measurement against a construct, scaffold, or bioink record. The endpoint accepts the Phase 1 §A.5 envelope plus the binary measurement payload (microscopy image, mechanical test stress-strain curve, qPCR plate, flow-cytometry FCS file). Read endpoints support filtering by test category, pass/fail status, and date range so QA teams can pull conformance reports for regulatory submissions. ## A.5 Bioreactor telemetry WebSocket The telemetry WebSocket multiplexes per-channel temperature, dissolved-oxygen tension, pH, glucose, lactate, perfusion flow rate, shear-stress estimate, and the camera image stream (compressed to 240p for bandwidth). Subscribers can filter by channel and by alarm threshold; the broker emits alarm-grade events on out-of-band readings (pH excursion, dissolved-oxygen drop) within the safety-loop's hard time budget. Reconnect uses the Phase 3 §A.6 nonce/skew protocol with monotonic counters per stream so brief network partitions do not collapse the audit trail. ## A.6 Rate-limit envelope 1000 req/h unauthenticated, 5000 req/h authenticated, 10000 req/h premium tier. Telemetry WebSocket subscriptions count separately and are bounded at 50 simultaneous subscriptions per credential. Bulk-export endpoints use cursor-based pagination via `?after=cursor&limit=N` (max 200) and emit `Retry-After` headers under load. --- ## 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.