The Products Your EtO Facility Can't Sterilize — And How VHP Opens the Door

Ethylene oxide works. That is not the question. The question is which products it works for — and the answer is becoming increasingly bounded as the medical device pipeline evolves toward materials and product architectures that EtO handles poorly or not at all.

EtO is optimized for a particular set of circumstances: heat-sensitive devices with relatively tolerant material profiles, standard packaging configurations, and no requirement for zero residue at the point of use. That set of circumstances describes a substantial share of the existing installed base. It does not describe the fastest-growing segments of the current development pipeline.

For EtO facilities evaluating where the next decade of growth comes from, four product categories represent concentrated opportunity — and a specific set of technical reasons why VHP is the better answer for each.

Why Product Categories Matter More Than Process Preferences

The conversation about EtO and VHP is often framed as a technology comparison: efficacy, cycle time, material compatibility, regulatory status. That framing is accurate but incomplete. The more consequential frame is market access.

An EtO-only facility cannot take on a cell therapy component. Not because EtO fails to sterilize it — but because the residue profile makes the product clinically unacceptable. The facility cannot bid on the contract. The revenue goes elsewhere. The customer relationship belongs to a competitor for the life of that product, and every next-generation product that follows from the same manufacturer.

Understanding why each of these product categories requires VHP is, at its core, understanding where EtO facilities are turning away business — and where the market will grow.

3D-Printed Porous Implants: The Geometry Problem

Additive manufacturing has transformed implant design. The ability to fabricate patient-matched implants with complex porous structures — lattices engineered for bone ingrowth, patient-specific spinal cages, customized acetabular cups — is driving a market valued at approximately $1.4 billion in 2026 and projected to reach nearly $4.8 billion by 2033, at a CAGR of over 19%. That growth is not slowing.

The same geometric complexity that makes these implants clinically valuable creates a sterilization problem that is specific to EtO. EtO sterilizes through gas penetration — the alkylating agent must reach and react with microbial DNA throughout the product. For porous implants, this is accomplished readily. The problem is what comes next: the gas must then be removed.

EtO residue clearance from porous structures requires extended aeration to allow the absorbed ethylene oxide and its primary breakdown products — ethylene chlorohydrin (ECH) and ethylene glycol — to desorb from the implant material. Research on 3D-printed medical devices confirms that porous and complex geometries create extended desorption timelines because the internal surface area available to absorb EtO scales with the porosity that defines the implant's clinical function.

The implications are operational and economic: extended aeration requirements lengthen product release timelines, consume floor space, and add cycle time that drives up per-unit cost. For high-value patient-specific implants with short manufacturing runs, this cost structure is difficult to absorb.

Recent peer-reviewed studies confirm an additional dimension. A 2026 study published in the Journal of Functional Biomaterials examining the effects of EtO and hydrogen peroxide vapor on 3D-printed carbon fiber-reinforced polycarbonate found that EtO sterilization resulted in approximately 20% reduced elongation at break and a lower glass transition temperature — indicating measurable loss of ductility and thermal stability in the base material. EtO's interaction with the polymer matrix is not inert. It induces chemical changes that can compromise the structural properties of the implant.

VHP addresses both problems. Hydrogen peroxide vapor penetrates complex geometries, achieves SAL 10⁻⁶ sterilization, and then decomposes completely to water and oxygen during the aeration phase. There are no residues that require extended clearance. There are no post-sterilization aeration periods measured in days. And comparative studies on 3D-printed polymer sterilization methods consistently identify hydrogen peroxide vapor as the preferred method for dimensional accuracy and material property preservation across the polymers most commonly used in additive manufacturing.

For EtO facilities, this represents a direct market access gap: every 3D-printed porous implant manufacturer evaluating contract sterilization has a specific technical reason to favor a VHP-capable partner over one that is EtO-only.

Bioabsorbable Implants: The Residue Equation

Bioabsorbable implants — fixation devices, scaffolds, sutures, and drug delivery substrates manufactured from polymers like polylactic acid (PLA), polyglycolic acid (PGA), and poly-L-lactide-co-glycolide (PLGA) — are designed to degrade in the body over time, replaced by native tissue or releasing a therapeutic payload as they dissolve. Their clinical value is precisely the material instability that makes conventional sterilization challenging.

Steam sterilization is disqualifying: the heat and moisture of autoclave conditions cause hydrolytic chain scission in aliphatic polyesters, compromising both mechanical properties and degradation kinetics before the product reaches the patient. Gamma irradiation induces polymer chain scission and crosslinking reactions that alter the degradation profile in ways that can change drug release behavior or mechanical performance. EtO operates at lower temperatures and avoids radiation-induced polymer damage — but it generates residues that require controlled clearance, and those residues persist in materials that are specifically designed to interact with biological tissues over extended periods.

The 2026 Pharmaceutical Research study on deep-vacuum VHP sterilization of PLGA, PLC, and TPU electrospun scaffolds provides the most current evidence: VHP sterilization preserved molecular weight and chemical integrity across all tested polymers, with FTIR confirming no chemical changes attributable to the sterilization process. The study concluded that VHP "emerges as a gentle, green, and residue-free approach that preserves scaffold morphology and performance" — language that reflects the clinical requirement precisely.

For bioabsorbable implants with direct tissue contact applications, the residue-free profile of VHP is not a preference. It is a product requirement. VHP decomposes to water and oxygen — leaving nothing behind in materials designed to be absorbed by the body.

The corollary for EtO facilities is direct: bioabsorbable orthopedic fixation devices, resorbable scaffolds for regenerative medicine applications, and PLGA-based drug delivery substrates represent product categories that must be sterilized with a method that leaves no residue. VHP is that method. EtO is not.

Cell Therapy Components: The Zero-Tolerance Standard

Cell therapy represents the most unambiguous case. CAR-T cell therapy, stem cell applications, tissue-engineered constructs, and other cell-based products are among the most complex and highest-value products currently entering the medical product pipeline. They are also among the most sensitive to chemical contamination.

ISO 10993-7 establishes residue limits for ethylene oxide and its metabolites in finished medical devices — and those limits are calibrated for conventional devices, not for products where cells will be in direct, sustained contact with device components. For cell-seeded scaffolds and cell therapy delivery devices, the tolerance for chemical residues that could affect cell viability is effectively zero.

EtO requires prolonged aeration to remove toxic residues before product release, and even following validated aeration protocols, trace residues and EtO reaction products remain measurable. Published research has documented EtO adduct formation with amino acid residues — specifically cysteine and methionine — in protein-containing biologics at residue levels within ISO limits. For cell therapy components, where cytotoxicity testing is a design control requirement, this is not a process variable to manage. It is a disqualifying characteristic.

VHP's decomposition chemistry resolves this constraint entirely. Hydrogen peroxide vapor breaks down to water and oxygen — leaving no residue capable of interacting with cells, growth factors, or biological coatings. For cell therapy delivery systems, scaffold matrices, and any device component that will be in direct sustained contact with viable cells, this is the only terminal sterilization method that satisfies the zero-tolerance residue standard without requiring aseptic manufacturing as the sole sterility assurance mechanism.

For EtO facilities, cell therapy components represent an entire product category that cannot be accommodated — not because EtO fails as a sterilization method, but because its residue profile is incompatible with the product's biological requirements. Every cell therapy manufacturer seeking terminal sterilization for a device component is looking for a VHP-capable partner. An EtO-only facility is not in the conversation.

Combination Products: The Compatibility Problem

Drug-device combination products occupy a regulatory and technical space that creates specific sterilization challenges — and EtO's compatibility profile is one of the more consequential constraints manufacturers face during development.

The FDA's own guidance on combination product development explicitly identifies terminal sterilization as a variable that can "alter certain drug or biological product critical quality attributes and, therefore, the active dose amount being delivered." That language is not incidental. It reflects the technical reality that combination products with drug coatings, drug-eluting polymer matrices, or biological constituent parts may be degraded, denatured, or chemically altered by the temperature, humidity, and chemical exposure conditions of EtO sterilization.

Drug-eluting stents illustrate the problem precisely: published research has documented measurable drug content loss attributable to EtO sterilization conditions — the heat and humidity required for cycle efficacy interact with the drug-polymer matrix in ways that can shift the device's elution kinetics and delivered dose. For a product whose therapeutic claim depends on controlled drug delivery, this is not an acceptable manufacturing variable.

Biologics-device combination products add a second layer of constraint. An EtO aeration cycle that is acceptable for a conventional device may leave residue levels that interact with the biologic constituent in ways that are difficult to characterize and harder to predict. The FDA's June 2024 draft guidance on essential drug delivery outputs for combination products reflects the increasing regulatory attention on constituent part interactions — including sterilization-induced changes — across the combination product submission pathway.

VHP operates at low temperatures — typically 25°C to 50°C — without the humidity conditions that EtO sterilization requires. It provides terminal sterilization without the chemical exposure profile that degrades drug coatings or interacts with biological constituent parts. For combination product developers, this means a shorter path through material compatibility assessment and a cleaner regulatory narrative on sterilization method selection.

For EtO facilities, combination products represent one of the fastest-growing product categories in the medical device pipeline — driven by the convergence of pharmaceutical innovation and device engineering in areas including targeted drug delivery, regenerative medicine, and implantable therapeutics. An EtO facility that cannot demonstrate VHP capability is not positioned to serve this market.

The Market Signal in the Development Pipeline

The through-line across these four categories is not difficult to read: the product categories that require VHP are the ones growing fastest. 3D-printed implants, bioabsorbables, cell therapies, and combination products are not niche or emerging markets. They are the current generation of medical device development — and the manufacturers behind them are making sterilization decisions now that will determine their contract sterilization relationships for the next decade.

EtO is not going away. It sterilizes half of all medical devices produced in the United States — approximately 20 billion units annually — and it will continue to do so. The case for VHP is not EtO's decline. The case is that a growing share of new products entering the market cannot be optimally sterilized by EtO, and every such product is a contract that goes somewhere else.

The facilities that recognize this are not replacing EtO capacity. They are adding VHP capacity alongside it — the "AND" model that allows a single facility to serve the full breadth of what the market now requires. The EtO chamber runs the product categories it handles best. The VHP system handles the categories EtO cannot serve.

SteriFlex: Designed for Product Complexity

PuroGen's SteriFlex platform is the operational implementation of this principle. Its programmable parametric architecture — independent control of VHP concentration, temperature, humidity, and cycle timing — was designed for exactly the product diversity that characterizes modern medical device manufacturing.

A 3D-printed porous implant requires different cycle parameters than a PLGA scaffold. A cell therapy delivery device requires validation criteria that are distinct from a drug-eluting stent. SteriFlex runs a validated cycle for each product type against its own parameter set and documentation trail. A fixed-cycle system cannot do this; the product diversity across these four categories demands programmable control as a prerequisite.

SteriFlex achieves SAL 10⁻⁶ in cycles as short as 20 minutes, operates with no toxic residue, and leaves no chemical footprint on processed materials. FDA Category A recognition and ISO 22441:2022 alignment provide the regulatory framework for submission across all four product categories. For EtO facilities evaluating VHP addition, SteriFlex is designed to operate alongside existing infrastructure — complement, not replace.

Frequently Asked Questions

**Why can't extended aeration solve EtO's residue problem for cell therapy components?**

Extended aeration removes absorbed EtO and reduces measurable residues, but the clearance requirement for cell therapy components is not defined by ISO 10993-7 limits alone. For products where cells will be in direct sustained contact with device components, the tolerance for any chemical residue capable of affecting cell viability is effectively zero. EtO aeration protocols are designed to meet established device safety limits — they are not designed to satisfy the zero-residue standard that cell-sensitive applications require. VHP's decomposition to water and oxygen addresses this at the process level rather than through post-sterilization clearance.

**Do 3D-printed porous implants always require VHP, or is it case by case?**

The sterilization method must be selected based on material properties, geometry, and the residue requirements of the specific application. For porous implants with complex internal geometries, EtO residue clearance challenges and extended aeration requirements create operational and economic constraints that make VHP the preferred choice in most cases. For dense-geometry 3D-printed devices without porosity concerns, EtO may remain a viable option — but the evaluation must account for the material interaction data that has emerged from recent sterilization studies on printed polymers.

**Are combination products automatically disqualified from EtO sterilization?**

No — EtO remains viable for certain combination products where drug-device compatibility has been demonstrated and residue levels do not affect therapeutic efficacy. The disqualification applies when the drug or biologic constituent is sensitive to the temperature, humidity, or chemical conditions of EtO, or when the residue profile affects drug quality attributes in ways that cannot be controlled to acceptable limits. The FDA's guidance on combination product development requires that sterilization be evaluated as a potential source of drug constituent degradation — the answer to that evaluation determines the appropriate method.

**How does VHP compare to gamma irradiation for bioabsorbable implants?**

Gamma irradiation induces polymer chain scission and crosslinking in aliphatic polyesters — the polymer class that includes PLA, PGA, and PLGA — which can alter degradation kinetics, mechanical properties, and drug release behavior. For bioabsorbable implants where the degradation profile is a design specification, radiation-induced polymer modification is a manufacturing risk that must be quantified and controlled. VHP sterilizes without ionizing radiation, leaving the polymer chemistry unaffected. The 2026 Pharmaceutical Research data on VHP sterilization of PLGA scaffolds confirms preserved molecular weight and chemical integrity — the baseline requirement for bioabsorbable applications.

**How does an EtO facility add VHP capability without disrupting existing operations?**

VHP sterilization systems are modular and can be commissioned within existing facility footprints without interfering with EtO operations. The two processes operate independently — validated and documented separately, running in parallel. There is no cross-contamination risk, no shared infrastructure requirement, and no operational dependency between the two modalities. PuroGen's implementation support model covers process development, IQ/OQ/PQ execution, and regulatory documentation preparation — allowing the facility to bring VHP capability online while existing EtO operations continue unchanged. For a more detailed look at the implementation pathway, see our guide on adding VHP capability to an existing sterilization facility.