Terminal Sterilization Research Articles

Acellular Dermal Matrix Sterility: Does It Affect Microbial and Clinical Outcomes Following Implantation?

Introduction:The use of acellular dermal matrices (ADMs) in breast reconstruction is a controversial topic. Recent literature has investigated the effects of ADM sterilization on infectious complications, although with varying conclusions. Previous work by our group showed no difference between aseptic and sterilized products immediately out of the package. In this study, we investigate the microbiologic profiles of these agents after implantation.Methods:In this prospective study, we cultured samples of ADM previously implanted during the first stage of tissue expander-based immediate breast reconstruction. A 1 cm2 sample was excised during the stage II expander–implant exchange procedure, and samples were incubated for 48 hours in tryptic soy broth. Samples with growth were further cultured on tryptic soy broth and blood agar plates. Patient records were also analyzed, to determine if ADM sterilization and microbial growth were correlated with infectious complications.Results:In total, 51 samples of ADM were collected from 32 patients. Six samples were from aseptic ADM (AlloDerm), 27 samples were from ADM sterilized to 10–3 (AlloDerm Ready-to-Use), and 18 samples were from products sterilized to 10–6 (AlloMax). No samples demonstrated bacterial growth. Only 5 patients experienced postoperative complications, of whom only 1 patient was infectious in nature. We failed to demonstrate a statistically significant correlation between sterility and postoperative complications.Conclusions:Our findings showed no difference in microbial presence and clinical outcomes when comparing ADM sterility. Furthermore, no samples demonstrated growth in culture. Our study brings into question the necessity for terminal sterilization in these products.

Effect of different sterilization methods on the properties of commercial biodegradable polyesters for single-use, disposable medical devices.

The increasing employment of non-degradable polymers based single-use, disposable medical devices have led to huge environmental pressure. Replacement of non-degradable polymers with biodegradable alternatives could be one solution. Since terminal sterilization is a necessary procedure for medical devices to eliminate infections, in this paper, the modifications of sterilization on the transparency, yellow index, dimensional stability and mechanical properties of commercial biodegradable poly(lactic acid) (PLA), poly(butylenes adipate-co-terephthalate) (PBAT) and their blends were investigated. The samples were prepared by compression molding and exposed to four sterilization treatments including ethylene oxide gas (EtO), saturated steam (SS), electron beam (EB), and hydrogen peroxide gas plasma (HPGP). It is concluded that EB can be applied for the sterilization of all the materials investigated, while SS and EtO are not recommended for PLA, and HPGP is not for PBAT and PLA/PBAT blends. This study demonstrates that, when a suitable sterilization process is chosen, PLA has potential to be used for transparent medical devices such as the barrel of syringes or microfluidic chips, while PBAT and PLA/PBAT blends for other non-transparent medical packaging applications.

Autoclavable and Injectable Cryogels for Biomedical Applications.

Prior to any clinical application, terminal sterilization of biomaterials is a critical process imposed by the Food and Drug Administration. Of all the methods available for sterilization, high-pressure steam sterilization such as autoclaving is the most widely used. While autoclave sterilization minimizes pathogen contamination, it can dramatically impact both structural and biological properties of biomaterials. It has recently been reported that injectable cryogels with shape memory properties hold great promises as 3D macroporous biomimetic scaffolds for biomedical applications including tissue engineering. In this study, the impact of autoclave sterilization on properties of a series of cryogels is measured. Unlike conventional hydrogels, cryogels made of natural polymers demonstrate a strong resilience to autoclave sterilization. This process does not alter either their macrostructural or unique physical properties including syringe injectability. The scaffolds' bioactive sites are preserved and autoclaved cryogels retain their excellent cytological compatibility post-autoclaving. Furthermore, autoclaved cryogels do not trigger a notable activation of primary murine bone marrow-derived dendritic cells suggesting a minimal risk for biomaterial-induced inflammation, which is further confirmed by an in vivo histologic analysis. In summary, these results further demonstrate the huge potential of cryogels in the biomedical field and their capacity to be translated into clinical applications.

Irradiation sterilization used for allogenetic tendon: a literature review of current concept.

Tendon injury is a very common type of sports trauma, and its incidence has increased over the past decades. Surgical reconstruction with tendon allograft has been increasingly used to restore the motor function and stability of the injured site. However, the risk of disease transmission caused by allogeneic tendon transplantation has been a major problem for tissue bank researchers and clinicians. In order to eliminate the risk of disease transmission, a process of terminal sterilization is necessary. Ionizing irradiation, including gamma irradiation and electron beam irradiation is the most commonly used method for the terminal sterilization, which has been widely proved to be able to effectively inactivate the contained pathogens. Nevertheless, some accompanying damage to the mechanical and histological properties of collagen fibers in tendons will be caused. Therefore, more and more studies have begun to pay attention to the protective effect of radiation protection agents, including the radical scavengers and cross-linking agents, in the irradiation sterilization of allogeneic tendons.

DETECTION OF IONIZING RADIATION TREATMENT IN GLASS USED FOR HEALTHCARE PRODUCTS.

The treatment with high doses of ionizing radiation is prescribed for the terminal sterilization of many healthcare products. In order to check the product irradiation, it may be useful to develop suitable detection methods. The aim of this work was to verify the suitability of the thermoluminescence (TL) and electron paramagnetic resonance (EPR) techniques to reveal illegal omission of radiation sterilization in glass used for blood test tubes. In particular, this work reports the results of the analysis performed on two batches of glass tubes provided by the same manufacturer. The results indicated that both TL and EPR techniques could reveal the damage induced by high doses of ionizing radiation in the glass allowing the identification of the tubes which were irradiated at the manufacture stage. The study provided also some information about the chemical composition of the two-batch glass.

Stabilization and Sterilization of Pericardial Scaffolds by Ultraviolet and Low-Energy Electron Irradiation.

Pericardial scaffolds have a wide spectrum of clinical applications ranging from patches for vascular reconstruction and abdominal wall defects to bioprosthetic heart valves. The current gold standard of tissue preparation involves disinfection and cross-linking using glutaraldehyde. However, glutaraldehyde-associated toxicity as well as rapid calcification and premature graft failure represent the major modes of failure.1 Therefore, a variety of alternative strategies for tissue conservation have been pursued. However, none of those strategies has substituted glutaraldehyde as the method of choice yet. Furthermore, safe sterilization procedures that are nondetrimental to the tissue's functionality are scarce. We have developed a novel procedure to stabilize and sterilize (S) acellular pericardial scaffolds combining photo-initiated ultraviolet cross-linking (U) with low-energy electron irradiation (LEEI). This SULEEI procedure avoids the use of glutaraldehyde and utilizes LEEI as effective sterilization method. A bioburden of 5.1 × 105 ± 4.6 × 105 viable bacteria could be successfully inactivated by SULEEI treatment applying a surface dose of 30.6 ± 2.8 kGy. By challenging high-density polyethylene foil stacks with >106 Bacillus pumilus spores in different depths and modeling the dose distribution within the scaffolds, a maximum sample thickness of 175 μm was determined for successful sterilization. Moreover, SULEEI treatment appeared nondetrimental to the ultimate tensile strength (17.6 ± 8.6 MPa vs. 17.4 ± 9.6 MPa) of the scaffolds compared with glutaraldehyde-treated pericardia. Cell number and overall metabolic activity of human endothelial cells were significantly higher on SULEEI-treated pericardia compared with control samples. In contrast, no cell proliferation could be detected on glutaraldehyde-treated pericardia. Thus, the SULEEI procedure may be a promising novel procedure for glutaraldehyde-free tissue preparation for pericardium-based tissue transplants and tissue engineering.Impact StatementPericardium-based tissue transplantation is a lifesaving treatment. Commercial glutaraldehyde-treated pericardial tissue exhibits cytotoxicity, which is associated with the accelerated graft failure. Replacement of glutaraldehyde has been suggested to overcome those drawbacks. In this study, we report a toxin-free method that combines tissue stabilization with a terminal sterilization. Our data indicate that the SULEEI procedure, which is part of an issued patent, may be a promising first step toward glutaraldehyde-free pericardium-based tissue transplants. Thus, our results may contribute to improving cardiovascular treatment strategies.

Elevating the standard of endoscope processing: Terminal sterilization of duodenoscopes using a hydrogen peroxide–ozone sterilizer

The health care community is increasingly aware of the processing challenges and infection risks associated with duodenoscopes owing to published reports of outbreaks and regulatory recalls. Studies have demonstrated that the current practices are inadequate for consistently producing patient-ready endoscopes. Alternatively, terminal sterilization would offer a greater margin of safety and potentially reduce the risk of patient infection. The purpose of this study was to evaluate the efficacy of a hydrogen peroxide-ozone sterilizer with regulatory clearance for terminal sterilization of duodenoscopes. Validation studies were performed under laboratory simulated-use and clinical in-use conditions. The overkill method study demonstrated a reduction of at least 6-log of Geobacillus stearothermophilus spores at half-cycle, providing a sterility assurance level of 10-6. In addition, the sterilizer achieved a 6-log reduction of G stearothermophilus in the presence of inorganic and organic soils in a simulated-use study. The clinical in-use study confirmed that the sterilizer achieved sterilization of patient-soiled duodenoscopes under actual use conditions. Simulated-use and clinical in-use studies demonstrated the efficacy of a hydrogen peroxide-ozone sterilizer for terminal sterilization of duodenoscopes. This offers health care facilities a viable alternative for duodenoscope processing to enhance patient safety as part of a comprehensive infection control strategy.

Effect of Electron Beam Sterilization on Three-Dimensional-Printed Polycaprolactone/Beta-Tricalcium Phosphate Scaffolds for Bone Tissue Engineering.

Providing customized geometries and improved control in physical and biological properties, 3D-printed polycaprolactone/beta-tricalcium phosphate (PCL/β-TCP) composite constructs are of high interest for bone tissue engineering applications. A critical step toward the translation and clinical applications of these types of scaffolds is terminal sterilization, and E-beam irradiation might be the most relevant method because of PCL properties. Through in vitro experimental testing of both physical and biological properties, it is proven in this article that E-beam irradiation is relevant for sterilization of 3D-printed PCL/β-TCP scaffolds for bone tissue engineering applications.

Corneal targeted Sertaconazole nitrate loaded cubosomes: Preparation, statistical optimization, in vitro characterization, ex vivo permeation and in vivo studies

Sertaconazole nitrate (STZ) is a poorly soluble antifungal drug commonly used for treating fungal skin infections. Introducing it as a new treatment option for the management of fungal keratitis, requires the development of a delivery system capable of targeting the infected cornea with an adequate STZ concentration. Hence, Sertaconazole nitrate loaded cubosomes (STZ-CUBs) were prepared, characterized and optimized based on a 33 central composite face-centred design. Optimized formulation (CUB-opt) showed maximum desirability (0.905), with solubilization efficiency (SE%) of 94.50 ± 0.51%, particle size (PS) of 216.55 ± 2.33 nm, polydispersity index (PDI) of 0.229 ± 0.11 and zeta potential (ZP) of 34.00 ± 6.93 mV. Under the transmission electron microscope, it showed discrete cubic shaped structures. Moreover, it exhibited a promising mucoadhesive behavior, terminal sterilization stability, and storage stability. Ex vivo corneal permeation study revealed its ability to enhance the steady state flux (Jss) and the permeability coefficient (KP) of STZ, compared to STZ-suspension. Finally, CUB-opt formulation was found to be safe on the corneal tissues in the in vivo corneal tolerance study, and demonstrated a superior corneal penetration power in the in vivo corneal uptake study.

A Proof of Principle Study of the Terminal Sterilization of Prefilled Syringes Using A Water Cascade Process

Abstract Background A new development in drug compounding is the production of ready-to-administer sterilized prefilled syringes. A challenge with these syringes is the method of terminal sterilization. There is no information available whether water cascade sterilization is a suitable method. We investigated the effect of this sterilization method on cyclic olefin (co)polymer (CCP/COC) syringes. Methods For two brands ten prefilled syringes were sterilized using water cascade sterilization. The closure integrity, stopper movement, weight, diameter and physical appearance were determined before and after sterilization. As sterility test, additional syringes were filled with tryptic soy broth (TSB) and sterilized. After fourteen days microbiological growth was determined. Results Closure integrity testing showed no dye penetration inside the syringe. Together with the results for weight this showed that closure integrity is guaranteed. No significant stopper movement, deviation in diameter or visual anomalies were observed. No microbiological growth in TSB was visible. Conclusions The results of this proof of principle study show that the physical and microbiological stability of the cyclic olefin (co)polymer syringes is guaranteed during sterilization using a water cascade sterilizer. These results do not rule out the necessity for further stability experiments (e. g. interaction with drug product) to further proof the concept.

A Paradigm Shift Toward Terminally Sterilized Devices.

Given the complexity of the sterilization process, and the risk involved in absence of strict adherence to the protocol described by the medical device manufacturers, terminally sterilized devices are emerging and being promoted in the field of medical practices. The characteristics associated with conventional reprocessing are demanding logistics, costs of delay, operations and adverse events, and unacceptable liability. Demanding logistics were a result of decoupled staff between the operating room and sterilize processing department, understaffed and high-volume processing with an additional burden due to inventory management and inefficient training. Other costs arose from upkeep, delay in operating room, and surgical-site infections. Liability arose from the repeatedly use of an unquantifiable process thus adding uncertainties, limited shelf life of the reprocessed implants, contingency of flash sterilization and introduction of newer technology with higher demand on cleaning performances. In contrast, terminally sterilized single-use devices do not carry any of the aforementioned-characteristics, deeming it to be the simplest solution to the current conundrum. This review serves to provide an evaluation of logistics, costs, and potential adverse effects, both directly and indirectly, associated with current practices in the sterile processing department, and also describes as to how the use of terminally sterilized devices can help circumvent those.

A Methodologic Approach for the Selection of Bio-Resorbable Polymers in the Development of Medical Devices: The Case of Poly(l-lactide-co-ε-caprolactone).

In the last decades bioresorbable and biodegradable polymers have gained a very good reputation both in research and in industry thanks to their unique characteristics. They are able to ensure high performance and biocompatibility, at the same time avoiding post-healing surgical interventions for device removal. In the medical device industry, it is widely known that product formulation and manufacturing need to follow specific procedures in order to ensure both the proper mechanical properties and desired degradation profile. Moreover, the sterilization method is crucial and its impact on physical properties is generally underestimated. In this work we focused our attention on the effect of different terminal sterilization methods on two commercially available poly(l-lactide-co-ε-caprolactone) with equivalent chemical composition (70% PLA and 30% PCL) and relatively similar initial molecular weights, but different chain arrangements and crystallinity. Results obtained show that crystallinity plays a key role in helping preserve the narrow distribution of chains and, as a consequence, defined physical properties. These statements can be used as guidelines for a better choice of the most adequate biodegradable polymers in the production of resorbable medical devices.

In-house cyclotron production of high-purity Tc-99m and Tc-99m radiopharmaceuticals

In the last years, the technology for producing the important medical radionuclide technetium-99m by cyclotrons has become sufficiently mature to justify its introduction as an alternative source of the starting precursor [99mTc][TcO4]- ubiquitously employed for the production of 99mTc-radiopharmaceuticals in hospitals. These technologies make use almost exclusively of the nuclear reaction 100Mo(p,2n)99mTc that allows direct production of Tc-99m.In this study, it is conjectured that this alternative production route will not replace the current supply chain based on the distribution of 99Mo/99mTc generators, but could become a convenient emergency source of Tc-99m only for in-house hospitals equipped with a conventional, low-energy, medical cyclotron. On this ground, an outline of the essential steps that should be implemented for setting up a hospital radiopharmacy aimed at the occasional production of Tc-99m by a small cyclotron is discussed. These include (1) target production, (2) irradiation conditions, (3) separation/purification procedures, (4) terminal sterilization, (5) quality control, and (6) Mo-100 recovery. To address these issues, a comprehensive technology for cyclotron-production of Tc-99m, developed at the Legnaro National Laboratories of the Italian National Institute of Nuclear Physics (LNL-INFN), will be used as a reference example.

Carbodiimide cross-linking counteracts the detrimental effects of gamma irradiation on the physical properties of collagen-hyaluronan sponges.

Collagen-based scaffolds are extensively used in biomaterials and tissue engineering applications. These scaffolds have shown great biocompatibility and versatility, but their relatively low mechanical properties may limit use in orthopaedic load-bearing applications. Moreover, terminal sterilization with gamma irradiation, as is commonly performed with commercial devices, presents concerns over structural integrity and enzymatic stability. Therefore, the goal of this study was to test the hypothesis that EDC/NHS cross-linking (10 mM/5 mM) can protect collagen-hyaluronan sponges from the damaging effects of gamma irradiation. Specifically, we evaluated compressive and tensile mechanical properties, enzymatic stability, porosity and pore size, and swelling ratio. Ultimate tensile strength and elastic modulus exhibited increases (168.5 and 245.8%, respectively) following irradiation, and exhibited over tenfold increases (1049.2 and 1270.6%, respectively) following cross-linking. Irradiation affected pore size (38.4% decrease), but cross-linking prior to irradiation resulted in only a 17.8% decrease. Cross-linking also showed an offsetting effect on the equilibrium modulus, enzymatic stability, and swelling ratio of sponges. These results suggest that carbodiimide cross-linking of collagen-hyaluronan sponges can mitigate the structural damage typically experienced during gamma irradiation, warranting their use in tissue engineering applications.

Development of stable liquid formulations for oligonucleotides

Oligonucleotide-based therapeutics have been implemented as a new therapeutic modality in biotech industry, which offers the opportunity to develop formulation platforms for robust parenteral formulations. The aim of this study was to gain a better understanding of stabilizing/de-stabilizing effects of different formulation parameters on unconjugated and N-acetylgalactosamine (GalNAc) conjugated single stranded oligonucleotides with locked nucleic acid modifications (LNA SSO), as model oligonucleotides. Various buffer systems, pH levels and different excipients were evaluated to optimize conditions for LNA SSO in liquid formulations. LNA SSO were exposed to different temperature conditions, mechanical stress as well as oxidative conditions, and the maximum feasible LNA SSO concentrations regarding handling and processing were determined. Finally, options for terminal sterilization of LNA SSO were evaluated. Results show that the tested LNA SSO were most stable under slightly alkaline conditions. A decrease in viscosity was best accomplished in the presence of spermine and lysine. Heat treatment and gamma irradiation caused high levels of degradation of the LNA SSO. Crucial formulation parameters, as identified in this study, should contribute to a significant increase in future productivity in drug product development for single-stranded oligonucleotides.

Effects of gamma irradiation and periodate oxidation on the structure of dextrin assessed by mass spectrometry

Sterilization of biomaterials by gamma irradiation should not change its structure, since this may affect also its bioactivity. In this work, dextrin and periodate-oxidized dextrin (ODEX), both irradiated and non-irradiated, were hydrolysed by α-amylase and the obtained oligosaccharides were fractionated by ligand-exchange/size exclusion chromatography and analyzed by matrix-assisted laser desorption/ionization (MALDI-MS) and electrospray ionization (ESI-MSn) mass spectrometry. This allowed the identification of structures formed during partial periodate oxidation, which displayed aldehyde groups in different positions of dextrin backbone, according to the type of residue which was oxidized. Importantly, gamma irradiation did not structurally change either dextrin or ODEX, showing that it can be used as suitable terminal sterilization method of these materials for biomedical applications. To our best knowledge, this is the first report using MS-based techniques to evaluate the effects of partial periodate oxidation and of gamma irradiation on polysaccharides and, in particular, on dextrin and its oxidized form.

The Effect of Different Sterilization Methods on Polypropylene Syringes

This presents the influence of gamma irradiation on Pharmacopeia specifications, mechanical and flow parameters of polypropylene (PP) syringes. There has been significant progress in the terminal sterilization of single-use, disposable medical devices with gamma radiation sterilization due to the growing awareness of toxic residues during the ethylene oxide (EtO) sterilization. PP is a widely used polymer for the production of syringes because of its excellent mechanical and thermal properties and has expanded continuously over the last decade. Although 25 kGy was generally recommended for the gamma radiation sterilization of medical products, this radiation dose is high enough to produce substantial damage. Electron spin resonance (ESR) characteristics of irradiated syringes were also studied at normal (25 °C, 60% relative humidity) and accelerated (40 °C, 75% relative humidity) stability test conditions. It was found that the chemical and radiolytic changes and sterility assurance levels (SAL) after gamma radiation sterilization were different in PP syringes. It was shown that for two commercial syringes, E1 and E3, a SAL of 10−4 could be attained with only 10 kGy, with there being less detrimental radiation effects on E1. The differences in the radiosensitivity of the propylene syringes could be due to the different formulations and manufacturing processes. The results indicated that a commercial syringe, identified as E1 could be safely sterilized with gamma irradiation as the radicals decay over a period of days under normal conditions and quenched much faster under stability conditions. Furthermore, ESR technique could be used successfully in monitoring the radiosterilization of this material. Additionally, the confirmation and validation of the SAL doses which are below 25 kGy, will decrease the time and cost of the sterilization with less damaging effects of ionizing irradiation.

Bioburden in transport solutions of human cardiovascular tissues: a comparative evaluation of direct inoculation and membrane filter technique.

All cardiac allograft tissues are under potential contamination, requiring a validated terminal sterilization process or a minimal bioburden. The bioburden calculation is important to determine the bacterial burden and further decontamination and disinfection strategies for the valve processing. The aim of this study was to determine the bioburden from transport solution (TS) of heart valves obtained from non-heart-beating and heart-beating donors in different culture methods. The bioburden from TS was determined in 20 hearts donated for valve allograft tissue using membrane filter (MF) and direct inoculation. Tryptic soy agar and Sabouraud plates were incubated and colonies were counted. Ninety-five percent of samples from this study were obtained from heart-beating donors. The warm ischemic time period for heart was 1.06 ± 0.74h and the cold ischemic time period was 25.66 ± 11.16h. The mean TS volume was 232.68 ± 96.67mL (48.5-550mL). From 20 samples directly inoculated on TSA agar plates, 2 (10%) were positive. However, when MF was used, from 20 samples in TSA, 13 (65%) were positive with a mean count of 1.36 ± 4.04CFU/mL. In Sabouraud plates, the direct inoculation was positive in 5 samples (25%) with a mean count of 0.24 ± 0.56CFU/mL. The use of MF increased the positivity to 50% (10 samples from a total of 20) with a mean of 0.28 ± 0.68CFU/mL. The positivity was superior using MF in comparison with direct inoculation (p < 0.05). The bioburden of TS is low and MF is the technique of choice due to higher positivity.

The Boil Test-Strategies for Resistance Determination of Microorganisms.

The terminal sterilization of drugs and devices is the most appropriate means of assuring patient safety in terms of infection prevention. Adoption of terminal sterilization processes requires a supporting and thorough program for control and monitoring of bioburden, especially if a parametric release program of sterilization is desired. Such a control program should necessarily assess and evaluate the associated bioburden (primarily spores), which may resist inactivation and challenge the sterilization cycle. The bioburden resistance can be evaluated by several means and procedures (e.g., the boil test); however, these procedures should be designed and implemented taking into consideration the nature of the spore and spore recovery. This short review describes the application of moist heat resistance for the terminal sterilization of drugs.LAY ABSTRACT: The terminal sterilization of drugs and devices is the most appropriate means of assuring patient safety in terms of infection prevention. Adoption of terminal sterilization processes requires a supporting and thorough program for control and monitoring of bioburden, especially if a parametric release program of sterilization is desired. This short review describes the application of moist heat resistance for the terminal sterilization of drugs.

Sterilization of Silastic Capsules Containing 17β-Estradiol for Effective Hormone Delivery in Mus musculus.

Silastic capsules are frequently used to study the physiologic effects of estrogen exposure in animal models. The Office of Laboratory Animal Welfare requires the sterilization of nonpharmaceutical-grade compounds before use. We compared 2 commonly used terminal sterilization methods-ionizing radiation (IR) and ethylene oxide (EO)-for their utility in sterilizing silastic capsules containing 0.05 or 0.1 mg 17β-estradiol (E2). E2-specific ELISA demonstrated that serum estrogen levels did not differ between mice implanted with 0.05-mg E2 capsules that were sterilized with IR or EO and those implanted with nonsterilized capsules. Likewise, mammary gland morphology and progesterone receptor expression and proliferation in mammary epithelium were similar among mice treated with E2 capsules, regardless of sterilization method, and pregnant day 15 mice. In addition, IR-sterilized 0.1-mg E2 pellets provided high serum E2. We conclude that neither ionizing radiation nor ethylene oxide degraded E2 or the cellulose matrix, suggesting that these methods of sterilization are appropriate to provide effective sterile hormone capsules for animal research.