Biomaterials Advanced — Next Generation

First-generation biomaterials prioritized bio-inertness — keep the immune response quiet, do not corrode, do not leach. Examples: titanium hip stems, PMMA bone cement, silicone implants, bare-metal coronary stents.

The second generation introduced bioactivity. Hench’s 45S5 Bioglass (1969) bonded to bone via apatite layer formation; hydroxyapatite coatings appeared on orthopedic stems; first-generation drug-eluting stents reduced restenosis.

The third generation — the focus of this note — is instructive and interactive. Materials engineered to elicit specific cellular responses, to remodel over time, to change shape, to release drugs on cue, and to integrate with native tissue at the molecular and mechanical level.

Key threads since 2010:

• Immunomodulatory biomaterials;
• 4D-printed shape-changing structures;
• Dynamic and stimulus-responsive hydrogels;
• Decellularized ECM scaffolds;
• Peptide-amphiphile self-assembly;
• Organ-on-chip and bioprinted tissues;
• Conductive and stretchable polymers for neural and skin electronics;
• ML-discovered material compositions.

Immunomodulatory biomaterials

The classical foreign body response (FBR) — protein adsorption, monocyte/macrophage adhesion, foreign body giant-cell formation, fibrous encapsulation — was treated as inevitable in first-generation device design. The shift began with recognition that material chemistry and topography can steer macrophage polarization on the M1 (pro-inflammatory, classically activated by IFN-gamma + LPS) versus M2 (pro-healing, alternatively activated by IL-4 + IL-13) axis.

Bryan Brown and Stephen Badylak (University of Pittsburgh McGowan Institute) systematically characterized macrophage response to acellular ECM scaffolds (Biomaterials 2009, 30:1482; Badylak Annu Rev Biomed Eng 2011, 13:27). M2/M1 ratio correlates with constructive remodeling — productive tissue regeneration — versus scar formation. Brown-Sicari-Badylak Tissue Engineering Part C 2014 quantified the macrophage signature as a predictive biomarker for scaffold success.

David Mooney (Harvard SEAS, Wyss Institute) engineered injectable scaffolds that recruit dendritic cells in situ for cancer vaccines. Mooney’s Nat Biotechnol 2015, 33:64 paper described WDVAX, the first FDA-IND in-situ cancer vaccine from a programmable polymer scaffold, which entered first-in-human trial 2013 (NCT01753089 melanoma). The group’s PLGA + GM-CSF + CpG + tumor antigen scaffolds polarize dendritic cell maturation in the implant niche. Spinout Novarx and Novartis collaborations followed.

Cytokine-releasing scaffolds: Jeffrey Hubbell (EPFL/Chicago) engineered IL-4 and TGF-beta fusion proteins with extracellular matrix-binding domains (super-affinity for collagen, fibrinogen, fibronectin). These localize cytokine release to the implant site avoiding systemic toxicity (Hubbell PNAS 2017, 114:E450; Nat Biomed Eng 2018). Hubbell’s spinout Anokion (founded 2012, Anokion-Astellas $200M+ partnership 2022) commercializes immune-tolerance-inducing biomaterial therapeutics.

James Anderson (Case Western, the foundational figure in FBR mechanisms — Semin Immunol 2008, 20:86) characterized M1/M2 polarization on PEG vs polypropylene mesh substrates. His “host response to implants” review remains canonical for graduate biomaterials training.

Hoffman-Stayton’s pH-responsive zwitterionic polycarboxybetaine (pCBMA) coatings — developed by Shaoyi Jiang (University of Washington; Nat Biotechnol 2013, 31:553) — demonstrated >3 months in-vivo without fibrous capsule formation. A radical departure from PEG, which loses its anti-fouling capability after weeks due to oxidative degradation.

Daniel Anderson and Robert Langer (MIT) screened 700+ alginate analogs and identified triazole-modified alginates that resist FBR for >6 months in primates around encapsulated islet cell grafts (Nat Biotechnol 2016, 34:345; Nat Mater 2017, 16:671). Basis for Sigilon Therapeutics (founded 2016, acquired by Eli Lilly 2023). The technology underpins ongoing clinical work on encapsulated cell therapy for type 1 diabetes and hemophilia.

4D printing and shape-memory polymers

“4D printing” — coined by Skylar Tibbits (MIT Self-Assembly Lab) in his February 2013 TED talk and TEDx Boston demonstration — refers to 3D-printed structures programmed to change shape, properties, or function over time in response to a stimulus (water, heat, light, magnetic field, pH). Tibbits et al Sci Rep 2014, 4:7422 demonstrated wet-folding 3D-printed multimaterial structures using hydrogel swelling against rigid struts. The conceptual leap: time becomes the fourth design dimension, with stimulus-driven actuation programmed into material composition and geometric anisotropy.

Jennifer Lewis (Harvard SEAS) added an active material vocabulary with direct ink writing of shape-morphing hydrogel composites bio-inspired by plant tropisms. Sydney Gladman, Lewis et al Nat Mater 2016, 15:413 demonstrated programmed orchid mimics using anisotropic cellulose nanofibril ink alignment. The “biomimetic 4D printing” approach encodes anisotropic cellulose fibril alignment in hydrogel inks to control swelling directionality. Lewis’s lab also developed embedded 3D printing of soft strain sensors and vascularized tissue constructs.

Shape-memory polymers (SMPs) — single-molecule structures with a programmable temporary shape that recovers to a permanent shape on stimulus (heat, light, water, magnetic). Lendlein and Langer (Andreas Lendlein, Robert Langer) developed biodegradable SMPs in Science 2002, 296:1673. The architecture: multiblock copolymers with hard (polyester glass-transition) and switching (crystallizing) segments. Langer’s 2009 Adv Mater 21:3410 review remains foundational. Lendlein continued SMP development at HZG/HHI Berlin and University of Potsdam. Applications include self-tying sutures (the original 2002 demo), self-expanding stents, self-deployable nerve guides, and percutaneously deliverable orthopedic implants.

Stimulus-responsive polymers exploited in 4D printing:

• PNIPAM (poly N-isopropylacrylamide) — LCST (lower critical solution temperature) at 32 °C; swells below, shrinks above body temperature. Used in thermoresponsive cell sheets (Teruo Okano, Tokyo Women’s Medical University — corneal epithelial cell sheets for keratoconjunctival reconstruction). CellSeed Inc Japan commercial product CEEC (cultured epithelial cell sheets) since 2017.

• Azobenzene-modified polymers — cis/trans isomerization on UV/visible light triggers macroscopic strain. Ikeda et al Nature 2003, 425:145 photodriven motion in liquid-crystal elastomers. Priimagi et al Adv Mater 2014, 26:2233 light-driven oscillators.

• pH-responsive PMAA, PDMAEMA — swell with pH change for controlled drug release in GI tract (release in alkaline intestine after acidic stomach).

• Magnetic-responsive elastomers with embedded Fe3O4 nanoparticles (Lewis Nat Mater 2017, 16:889 ferromagnetic soft materials). Used in remotely controlled soft robots and capsule endoscopy steering.

• Liquid-crystal elastomers (LCEs) — Mark Warner-Ed Terentjev Cambridge classic theory; Tim White Air Force Research Laboratory programmable LCE deformations Nature 2015 514:455.

Boyuan Liu et al Sci Adv 2021 demonstrated 4D printing of voxel-resolution actuating hydrogel composites with programmable bending kinematics.

Injectable and dynamic hydrogels

Kristi Anseth (CU Boulder, AIChE Bioengineer of the Year 2018, NAE 2018) developed photoinitiated thiol-ene click chemistry for in-situ-formed PEG hydrogels. Fairbanks-Anseth Macromolecules 2009, 42:211 introduced the norbornene-thiol photo-click — fast, biocompatible, cytocompatible covalent crosslinking for cell encapsulation. PEG-thiol-ene chemistry is now standard for 3D cell culture and stem-cell expansion. Commercial reagent products from Stemcell Technologies, Mimetas (OrganoPlate), and Cell Guidance Systems serve this market.

Dynamic covalent chemistry (DCC) — reversible bonds (boronate esters, hydrazones, disulfides, Diels-Alder adducts, imines) — gives hydrogels stress-relaxation matching native tissue. David Mooney’s lab demonstrated that hydrogel viscoelasticity controls stem-cell fate decisions more strongly than substrate stiffness in many contexts:

• Chaudhuri-Mooney Nat Mater 2016, 15:326 — viscoelastic alginate hydrogels with tunable stress relaxation;
• Chaudhuri Cell Stem Cell 2017, 20:198 — MSC differentiation under viscoelastic matrix conditions.

Sarah Heilshorn (Stanford) engineered MITCH (mixing-induced two-component hydrogels) using engineered protein crosslinkers (Wong-Heilshorn Biomacromolecules 2009, 10:2540) — injectable, shear-thinning, recovering — for cell delivery.

Adam Engler-Discher’s substrate-stiffness paradigm (Engler-Discher Cell 2006, 126:677 — MSC fate guided by elastic modulus matching tissue) drove a decade of “mechanotransduction” research. Spatial stiffness gradients are now engineered into hydrogel scaffolds for:

• Neural regeneration (graded soft → stiff to match white-to-gray matter);
• Cardiac patches (sub-kPa for fetal-like to ~10 kPa adult ventricle);
• Gradient bone-to-cartilage interfaces (Spiller-Doloff scaffolds);
• Tendon-bone insertion mimics.

Self-healing hydrogels exploit dynamic non-covalent or reversible-covalent crosslinks:

• Cucurbit[8]uril host-guest chemistry (Oren Scherman, Cambridge);
• Hydrogen-bonded ureidopyrimidinone (UPy) supramolecular networks (E W “Bert” Meijer, TU Eindhoven);
• Metal-coordinated catechol chemistry (Niels Holten-Andersen MIT, Phil Messersmith Northwestern; mussel-inspired DOPA polymers);
• Boronate ester crosslinks (Sumerlin, Florida; Brendan Mahon UT Austin).

These underpin Gecko-style reversible adhesives and self-repairing soft tissue analogs. Tissium (Paris spinout from Robert Langer + Paris Descartes Université) developed photoactivated polymer adhesives for sutureless tissue repair, with CE Mark for nerve repair 2022 and ongoing FDA trials.

Peptide-amphiphile self-assembly

Sam Stupp (Northwestern, founder Simpson Querrey Institute for BioNanotechnology) developed peptide amphiphiles (PAs) that self-assemble into high-aspect-ratio nanofibers in aqueous solution (Hartgerink-Beniash-Stupp Science 2001, 294:1684). PAs comprise four design elements:

• A hydrophobic alkyl tail (typically C16 palmitoyl);
• A beta-sheet-forming peptide region (often VVAA or LLLL);
• A charged peptide region (acidic or basic);
• A bioactive epitope at the solvent-exposed end.

Assembly into 5-10 nm-diameter nanofibers with bioactive ligand density tunable from sub-nanomolar to molar effective concentrations.

Therapeutic applications:

• IKVAV-PA nanofibers (laminin-derived) for neural progenitor differentiation (Silva-Stupp Science 2004, 303:1352) — promoted neurite outgrowth and reduced astrogliosis in spinal cord injury models.
• RGDS-PA nanofibers for bone regeneration with synergistic mineralization.
• VEGF-mimetic PAs for vascularization (Webber-Stupp PNAS 2011, 108:13438 — supramolecular angiogenic scaffolds).
• “Dancing molecules” — Stupp Science 2021, 374:848 — PAs with mechanically dynamic supramolecular motion that drive partial recovery of locomotion in mouse spinal cord injury. Spinout Amphix Bio (founded 2022) for Phase 1 SCI trial anticipated 2025-2026.
• Anti-PD-L1 PAs for cancer immunotherapy (Stupp 2024).

Other PA practitioners and extensions:

• Matthew Tirrell (Chicago, formerly UCSF and Berkeley) — coiled-coil peptide assembly;
• Honggang Cui (Johns Hopkins) — drug-conjugated PA prodrugs;
• Joel Schneider (NCI) — beta-hairpin self-assembling peptides;
• Jeffrey Hartgerink (Rice) — multi-domain peptides and collagen mimetic assemblies.

The collective PA toolkit extends to anti-microbial peptides, vaccine adjuvants (peptide nanofibers as antigen scaffolds), and injectable hydrogels via charge complementarity.

Decellularized ECM scaffolds

Stripping a tissue or organ of cellular content while preserving the extracellular matrix architecture creates a scaffold that retains tissue-specific signals. Decellularization reagents and protocols:

• Ionic detergents: SDS (most aggressive, strips DNA but can damage GAGs);
• Non-ionic detergents: Triton X-100 (gentler, often combined with SDS);
• Sodium deoxycholate (intermediate aggressiveness);
• Enzymatic: trypsin, DNase, RNase removal of residual nucleic acids;
• Physical: freeze-thaw, hypertonic-hypotonic cycling.

Preserved matrix components: collagen and elastin three-dimensional structure, glycosaminoglycans (GAGs), vascular tree, basement-membrane laminins.

Doris Taylor (then Univ Minnesota, now Texas Heart Institute, currently with Organamet Bio Inc) demonstrated whole-organ decellularization of rat hearts followed by recellularization with rat neonatal cardiomyocytes producing beating constructs (Ott-Taylor Nat Med 2008, 14:213) — the field-defining paper of perfusion-decellularization. Harald Ott (MGH/Harvard, postdoctoral fellow with Taylor) extended the technique to:

• Lung (Nat Med 2010, 16:927);
• Kidney (Nat Med 2013, 19:646);
• Human-scale lungs and limbs.

Anthony Atala (Wake Forest Institute for Regenerative Medicine) had earlier reported tissue-engineered bladders implanted in seven young patients with myelomeningocele (Atala et al Lancet 2006, 367:1241), using patient cells on PGA-collagen composite scaffolds — the first FDA-IND tissue-engineered organ in humans. Atala’s group continues with bioprinted skin, liver, and kidney constructs.

Paolo Macchiarini’s decellularized trachea transplants (2008 Bristol Lancet 372:2023; subsequent cases at Karolinska 2011-2013) became the field’s biggest scandal. Multiple patients died. Papers retracted (Lancet retraction 2018). Karolinska investigations led to criminal proceedings. Macchiarini criminally convicted in Sweden June 2022 (reduced to suspended sentence on appeal 2023). The episode chilled clinical translation of decellularized organs and led to stricter ethical oversight in regenerative medicine, especially around the boundary between research and clinical care.

Modern progress:

• Recellularized rat liver lobes maintain function for hours-days in vitro (Uygun-Yarmush Nat Med 2010, 16:814 — MGH/Harvard);
• Miromatrix Medical (founded 2010 by Doris Taylor, acquired by United Therapeutics 2023 for $91M) pursues clinical-scale recellularized livers and kidneys;
• Organamet Bio pursues recellularized cardiac patches;
• FibroBiologics (Nasdaq: FBLG, 2023 IPO) develops fibroblast-based therapeutic candidates including ECM scaffold + fibroblast constructs.

Commercial decellularized acellular matrix products in clinical use:

• AlloDerm (LifeCell, acquired Allergan 2017 then AbbVie 2020) — human dermal matrix;
• SurgiMend (Integra LifeSciences) — fetal bovine dermal matrix;
• XenMatrix (Bard) — porcine dermal matrix;
• CorMatrix ECM (acquired Aziyo Biologics) — porcine SIS for cardiac and vascular use;
• Strattice (Allergan) — porcine non-crosslinked dermal matrix;
• AlloMend, FlexHD, Permacol — competing dermal matrix products in breast reconstruction.

3D-bioprinted tissues and organs

Bioprinting deposits cell-laden bioinks layer-by-layer using extrusion, inkjet, or laser-assisted methods. Common bioinks:

• Alginate (Ca2+ crosslinked, widely used, biocompatible);
• GelMA (gelatin methacryloyl, photocrosslinked);
• Fibrin (biological, supports cell adhesion);
• Decellularized-ECM-derived inks (dECM bioinks, tissue-specific);
• Sacrificial Pluronic F-127 (for vascular templating);
• PEG-based synthetic bioinks (Anseth thiol-ene chemistry).

Commercial and clinical bioprinting players:

• Organovo (NYSE:ONVO, peaked 2013 at ~$13/share) printed liver and kidney tissue constructs marketed for drug toxicity testing (exVive3D Liver, 2014). Pivoted away from bioprinting 2020 to focus on therapeutics (FXR341 inflammatory bowel disease).

• Cellink (Stockholm, now BICO Group, founded 2016 by Erik Gatenholm and Hector Martinez) supplied bioprinters globally. Acquired Visikol, MatTek, Discover Echo, Allegro 3D, and several adjacencies; reverse-merged into bigger life-sciences group.

• Aspect Biosystems (Vancouver) Lab-on-a-Printer microfluidic bioprinting platform produced insulin-producing pancreatic islet bioinks. Aspect-Novo Nordisk partnership 2023 ($75Mupfront,upto$650M milestones) on bioprinted islets for type 1 diabetes; Phase 1 anticipated mid-2026.

• 3D Systems Bioprinting — acquired Volumetric 2021 for vat-photopolymerization bioprinting at high resolution; acquired Allevi 2021 for extrusion bioprinting.

• Inventia Life Science (Sydney) — RASTRUM digital bioprinter for 3D cell culture, partnership with Pfizer for drug discovery.

• Prellis Biologics (San Francisco) — 2-photon polymerization for vascular tissue scaffolds at sub-micron resolution.

• BioLife4D — cardiac tissue bioprinting (NASDAQ:BLFE planned IPO).

• T&R Biofab (Korea) — large-scale bioprinted skin and bone constructs.

Vascularization remains the binding constraint for thick tissue construction. Jennifer Lewis SWIFT (sacrificial writing in functional tissue, Skylar-Scott-Lewis Sci Adv 2019, 5:eaaw2459) embeds sacrificial vascular networks in dense organ-building-block matrices. Enables perfused thick tissue constructs (>1 cm) with embedded vasculature.

Mark Skylar-Scott (Stanford spinout from Lewis lab) founded Trestle Biotherapeutics for pediatric kidney constructs and Curi Bio (separate venture) for cardiac and skeletal-muscle constructs.

United Therapeutics 3D Bioprinting Organ Manufacturing — Lung Biotechnology subsidiary, Manchester NH and Bothell WA facilities. The “3D Bio-Lab” for lung-scaffold xenotransplantation engineering complementing United Therapeutics’ Revivicor pig xenotransplant program.

Xenotransplantation regulatory traction milestones:

• First genetically modified pig kidney transplanted into a brain-dead human (Robert Montgomery NYU September 2021);
• First pig kidney into living patient (Richard Slayman MGH March 16, 2024, died May 11, 2024 of unrelated causes);
• Pig heart transplants by Bartley P Griffith at University of Maryland (David Bennett Sr January 2022, died 2 months later; Lawrence Faucette September 2023, died 6 weeks later);
• Towana Looney pig kidney transplant NYU November 2024 (FDA-cleared compassionate-use, longest pig-organ survival in living patient).

These cases underpin regulatory traction for xeno-derived tissue engineering and parallel the bioprinted-organ pipeline.

Microneedle drug delivery

Mark Prausnitz (Georgia Tech, Regents Professor and director of the Center for Drug Design Development and Delivery) pioneered solid, dissolving, and hollow microneedle arrays for transdermal vaccine and drug delivery. Foundational papers: Prausnitz-Mitragotri Nat Rev Drug Discov 2004, 3:115; Prausnitz Annu Rev Chem Biomol Eng 2017, 8:177.

Dissolving polymer microneedles (PVA, PVP, dextran, hyaluronic acid) loaded with vaccine antigen dissolve in the skin within minutes, eliminating sharps disposal and cold-chain dependence. The patient-self-administration pathway makes pandemic-vaccine distribution dramatically simpler.

Clinical translation:

• Vaxxas (Brisbane Australia, founded 2011 from UQ Mark Kendall lab) — Nanopatch HD-MAP (high-density microarray patch). COVID-19 vaccine HD-MAP Phase 1 results 2022 with Merck COVID-19 candidate. Pediatric measles-rubella WHO-funded program 2024.

• Micron Biomedical (Atlanta GA, Prausnitz spinout 2016) — dissolving microarray patches. Measles-rubella Phase 1/2 trial in The Gambia 2022-2023 reported May 2024 — non-inferior immunogenicity vs subcutaneous injection (Lancet Infect Dis 2024).

• Verndari (Sacramento CA) — VaxiPatch for flu vaccine, COVID boosters; Phase 1 2022-2023.

• Kindeva Drug Delivery — microarray patches for biologics; Eli Lilly partnership for GLP-1 microneedle programs.

• Sorrento Therapeutics RAPID — COVID-19 saliva test, transdermal patch portfolio.

• Zosano Pharma (defunct 2022) — M207 zolmitriptan microneedle migraine therapy FDA rejection 2020 over manufacturing, company wound down.

Cardiac patches and engineered heart tissue

Engineered heart tissue (EHT) — collagen/fibrin scaffolds seeded with cardiomyocytes (typically iPSC-derived) — has progressed from rodent proof-of-concept to human pilot trials. Foundational rodent work: Eschenhagen et al, Hamburg, 1997-2000s; later extensions by Bursac (Duke), Tulloch, and Murry (University of Washington).

The German Heart Center BHF-HepaT1 trial (Hamburg Eschenhagen group, Nat Med 2024, 30:2257) implanted iPSC-derived heart patches in dilated cardiomyopathy patients with reported partial functional recovery — the first publication of clinical iPSC cardiac patch outcomes.

Clinical-stage cardiac regenerative pipeline:

• Heartworks (UCSF Deepak Srivastava lab) — iPSC-cardiomyocyte cell therapy;
• Tenaya Therapeutics (Nasdaq:TNYA) — gene therapy for hypertrophic cardiomyopathy MYBPC3;
• BioCardia (CardiAMP autologous mesenchymal precursor cells, Phase 3 ongoing);
• Renovacor (acquired by Rocket Pharmaceuticals 2023 — BAG3 gene therapy);
• Cellprothera (France) — ProtheraCytes autologous CD34+ cells for post-MI;
• Help Therapeutics (China) — allogeneic iPSC cardiomyocyte injection.

Bioprinted vascularized cardiac patches remain pre-clinical but advancing — major academic programs at TAU (Tal Dvir), University of Minnesota (Doris Taylor before Texas Heart Institute move), and BioLife4D commercial development.

Engineered living materials

Synthetic-biology-derived living materials use engineered microbes as the active component. Examples:

• BioMASON (Raleigh NC, founded 2012 by Ginger Krieg Dosier) — Sporosarcina pasteurii bacteria precipitate calcium carbonate cementing aggregate into biocement bricks. CO2 footprint ~10-30% vs Portland cement; commercial paver products since 2020.

• MycoWorks (San Francisco, founded 2013) — Mycelium-leather alternative (“Reishi”) used by Hermès for the Sylvania bag launched 2021. SF facility plus South Carolina production scale-up.

• Ecovative Design (Green Island NY, founded 2007 by Eben Bayer and Gavin McIntyre) — Mycelium-based packaging (replaces EPS foam), insulation, leather analogs. Customers include IKEA and Dell. Recent Forager FineEarth fashion-leather pivot.

• Cambrium (Berlin, founded 2020) — engineered animal-free collagen for skincare; partnered with L’Oréal 2024.

• Modern Meadow (NJ, founded 2011, pivoted 2019 from leather to BioAlloyed biomaterials).

• LanzaTech (NASDAQ:LNZA) — engineered bacteria converting industrial CO emissions to ethanol and chemicals.

• Bolt Threads (defunct in textiles 2023, continues skincare) — engineered spider silk (Microsilk) and Mylo mycelium leather.

• AMSilk (Munich) — biotech spider-silk biopolymer for medical sutures and adidas Futurecraft.Biofabric shoes.

Drug-eluting stents and DLC coatings

Coronary stent evolution illustrates iterative biomaterial sophistication:

• Bare metal stents (BMS) — 1986 first (Palmaz-Schatz, JJIS Cordis); subacute thrombosis 5-15%, restenosis 20-40%.
• First-generation DES — Cypher (Cordis JJ, sirolimus-eluting, polylactic-acid-co-glycolic-acid coating; FDA 2003), Taxus (Boston Scientific, paclitaxel-eluting; FDA 2004). Restenosis dropped to ~5-10% but late stent thrombosis emerged from delayed endothelialization on persistent polymer.
• Second-generation DES — Endeavor zotarolimus (Medtronic 2008), Xience everolimus (Abbott 2008, Cobalt-chromium thin-strut platform), Resolute zotarolimus (Medtronic 2010). Thin struts + biocompatible fluoropolymer or PVDF-HFP coating.
• Bioabsorbable polymer DES — Synergy (Boston Scientific, FDA October 2015) with PLGA abluminal coating that fully absorbs in ~4 months leaving BMS underneath.
• Polymer-free DES — BioFreedom (Biosensors International) — drug embedded in microporous abluminal surface, no polymer; LEADERS FREE trial 2015 NEJM 373:2038.
• Fully bioabsorbable scaffold (BVS) — Absorb (Abbott PLLA-based, FDA July 2016) — withdrawn September 2017 after ABSORB III trial showed elevated MACE at 3 yr. The fully resorbable concept survives in Magmaris (Biotronik, magnesium-alloy), Iberis FANTOM (Reva Medical), Fortitude (Amaranth).

Diamond-like carbon (DLC) — amorphous sp2/sp3 carbon coatings deposited by PECVD or sputtering — provide ultra-low thrombogenicity, wear resistance, and chemical inertness on titanium and CoCr orthopedic implants and oxygenator components. Sulzer, B Braun, Stryker employ DLC coatings on bearings; Maquet ECMO oxygenators use heparin-coated polymethylpentene fibers complemented by surface modifications.

Bioactive ceramics and bone scaffolds

Bioglass evolution past Hench’s 45S5 (1969):

• 45S5 Bioglass (Novabone, Vivoxid, putties) — bonds to bone via apatite layer formation.
• Strontium-doped bioglasses (StronBone, Stupp’s QQQ scaffolds) — strontium promotes osteoblast activity and inhibits osteoclast resorption; clinical strontium ranelate (Servier Protelos) for osteoporosis withdrawn 2017 over cardiovascular safety but Sr-bioactive implant coatings continue.
• Mesoporous bioglasses (MBG) — Maria Vallet-Regí (Complutense Madrid) Acta Biomaterialia 2006 onward; ordered nanopore architecture for drug loading.
• 3D-printed Sr/Cu/Zn-doped scaffolds for vascularization and antimicrobial activity (Lewis lab et al).

Hydroxyapatite, beta-tricalcium phosphate (Vitoss, ChronOS), biphasic calcium phosphate (MasterGraft, Ossano) remain the bone-graft-substitute workhorses.

Piezoelectric biomaterials

Piezoelectric polymers PVDF (polyvinylidene fluoride) and its copolymer P(VDF-TrFE) convert mechanical strain to electrical charge, mimicking bone’s natural piezoelectricity (Fukada-Yasuda Jpn J Appl Phys 1964). Applications:

• PLLA (poly-L-lactic acid) piezoelectric scaffolds for bone regeneration — Cees Otto-Ben Feringa direction; Yadav et al Adv Mater 2017 PLLA membranes for bone defect healing.
• BaTiO3 (barium titanate) nanoparticle-loaded scaffolds (Tang-Gao Biomaterials 2017).
• Self-powered implants — Dagdeviren-Rogers (Univ Illinois, MIT) PVDF energy harvesters on lung and diaphragm for pacemakers (PNAS 2014, 111:1927).
• Marine ZnO nanowires for biological-piezo sensing (Wang Georgia Tech).

Conductive polymers for neural and retinal electrodes

Conductive polymers solve the impedance and biocompatibility mismatch between metal electrodes and neural tissue. PEDOT:PSS (poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate) is the workhorse — orders-of-magnitude lower impedance than Pt/Ir at neural-recording frequencies, gentle on cortex.

George Malliaras (Cambridge UK, formerly École des Mines) developed PEDOT:PSS organic electrochemical transistors (OECTs) and conformal cortical electrode arrays (NeuroGrid Khodagholy-Buzsáki Nat Neurosci 2015, 18:310). Polypyrrole (PPy) and polyaniline (PANI) provide additional conductive-polymer chemistries.

Argus II retinal prosthesis (Second Sight Medical Products) — first FDA-approved retinal prosthesis 2013 for retinitis pigmentosa, 60-electrode array; Second Sight discontinued support 2019 leaving implant recipients without firmware updates (ethical case study). PRIMA (Pixium Vision Paris, Daniel Palanker Stanford collaboration) — photovoltaic subretinal implant, 378 photodiode pixels, CE Mark 2024 for late-stage geographic atrophy AMD; Phase 3 in EU 2024-2025.

Neuralink N1 device (rolled out in clinic January 2024 with first patient Noland Arbaugh) employs flexible polymer probe threads with 1024 electrodes inserted by R1 surgical robot — design lineage traces to Polina Anikeeva (MIT), Charles Lieber (Harvard, his syringe-injectable mesh electronics), and Rogers stretchable bioelectronics work.

Wearable bioelectronics

John Rogers (Northwestern, formerly Univ Illinois) developed epidermal electronics — ultrathin (~5 µm), flexible, stretchable sensor arrays that conform to skin (Kim-Rogers Science 2011, 333:838; Webb-Rogers Nat Mater 2013, 12:938). Spinouts: MC10 (acquired by Medidata Solutions 2020) developed the BioStamp Research Connect platform. Rogers Soft Bioelectronics consortium with Stanford and UPenn.

Zhenan Bao (Stanford) developed intrinsically stretchable transistors and self-healing electronic skin (Bao Nature 2016, 539:411). C3 Nano, Cardea Bio, PsiQuantum trace back to her group.

Empatica (Boston, MIT Media Lab spinout 2011 by Rosalind Picard) — wrist-worn Embrace and Embrace2 (FDA cleared 2018 for seizure detection in epilepsy), E4 Wristband for research, EmbracePlus (2022). Acquired Mindstrong 2022 for digital biomarkers.

Whoop, Oura Ring, Apple Watch, Fitbit/Google extend consumer-grade biosensing; medical-grade equivalents are the Eko Core stethoscope (FDA cleared), iRhythm Zio patch (ECG, FDA cleared 2009 with continued upgrades), Bardy Diagnostics Carnation Ambulatory Monitor (acquired Hill-Rom 2021).

ML-driven materials discovery

Markus Buehler (MIT) applies deep learning, transformers, and generative AI to predict and design biomaterial sequences from natural protein motifs (spider silk peptide design, mycelium composites; Buehler Nat Comput Sci 2022, 2:75; ProteinGPT 2023). Material-LLMs (such as Buehler’s MateriaLLM 2024) for inverse design of mechanical-property-targeted biopolymers.

DeepMind AlphaFold2 (Jumper et al Nature 2021, 596:583) and AlphaFold3 (May 8, 2024) transformed structural biology, enabling rapid prediction of folded structures for designed peptide amphiphiles and engineered scaffold proteins. Baker lab’s RoseTTAFold All-Atom (2023) and ProteinMPNN (2022 Science 378:49) make de novo protein-based biomaterials practical.

Aspuru-Guzik (Toronto) and Schoenholz (Google) demonstrate closed-loop autonomous experimentation in soft-matter formulation discovery (mob-lab style).

3D-printed lattices for orthopedic and dental implants

Selective laser melting (SLM) and electron-beam melting (EBM) of Ti6Al4V or CoCrMo produce trabecular-mimetic porous structures matching bone modulus and promoting osseointegration. Major platforms:

• EOS (Krailling Germany) — EOS M 290, M 300-4, M 400 — workhorse SLM systems used by Stryker, Zimmer Biomet, Smith+Nephew.
• 3D Systems ProX DMP 320, DMP Flex 350 — used by ConforMIS for custom knee implants.
• GE Additive (formerly Arcam EBM, acquired 2016) Q-series — titanium acetabular cups and dental abutments.
• VELO3D Sapphire — large-format laser powder-bed for aerospace + medical.
• nTopology (now nTop) — implicit-geometry generative software for lattice-structure design; widely adopted in orthopedic design (Restor3d, Lima Corporate, ConforMIS, Stryker Tritanium cervical cage commercial since 2014).
• 3D Systems titanium acetabular cup, Stryker Tritanium PL posterior lumbar spine cage (FDA cleared 2014).

ConforMIS (NASDAQ:CFMS, later acquired by Restor3d 2024) pioneered patient-specific 3D-printed knee implants using preoperative CT. Lima Corporate Trabecular Titanium (TT) — commercial since 2007 — hip and shoulder porous implants.

Glass and ceramic 3D printing (Glassomer GmbH, Lithoz CeraFab) extend the technology toward bone-bonding bioceramic implants.

Adjacent

• biomaterials
• soft-matter-and-self-assembly
• structural-biology
• prosthetics-rehabilitation
• synthetic-biology
• additive-manufacturing