Sterilization of gentamicin containing collagen/PLGA microparticle composites

Local administration of irinotecan using an implantable drug delivery device stops high-grade glioma tumor recurrence in a glioblastoma tumor model

The treatment for Glioblastoma is limited due to the presence of the blood brain barrier, which restricts the entry of chemotherapeutic drugs into the brain. Local delivery into the tumor resection margin has the potential to improve efficacy of chemotherapy. We developed a safe and clinically translatable irinotecan implant for local delivery to increase its efficacy while minimizing systemic side effects. Irinotecan-loaded implants were manufactured using hot melt extrusion, gamma sterilized at 25 kGy, and characterized for their irinotecan content, release, and drug diffusion. Their therapeutic efficacy was evaluated in a patient-derived xenograft mouse resection model of glioblastoma. Their safety and translatability were evaluated using histological analysis of brain tissue and serum chemistry analysis. Implants containing 30% and 40% w/w irinotecan were manufactured without plasticizer. The 30% and 40% implants showed moderate local toxicity up to 2- and 6-day post-implantation. Histopathology of the implantation site showed signs of necrosis at days 45 and 14 for the 30% and 40% implants. Hematological analysis and clinical chemistry showed no signs of serious systemic toxicity for either implant. The 30% implants had an 80% survival at day 148, with no sign of tumor recurrence. Gamma sterilization and 12-month storage had no impact on the integrity of the 30% implants. This study demonstrates that the 30% implants are a promising novel treatment for glioblastoma that could be quickly translated into the clinic.

Large-Scale Development of Antibacterial Scaffolds: Gentamicin Sulfate-Loaded Biodegradable Nanofibers for Gastrointestinal Applications

The ever-increasing demands of modern medicine drive the development of novel drug delivery materials. In particular, nanofibers are promising for such materials due to their favorable properties. However, most development is still carried out through laboratory techniques that do not allow extensive and reproducible characterization of materials, which slows medical research. In this work, we focus on the large-scale fabrication and testing of specific antibacterial nanofibrous materials to prevent the postoperative complications associated with the occurrence of bacterial infection. Poly-ε-caprolactone with gentamicin sulfate (antibiotic) in different concentrations was electrospun via a needleless device. The amount of antibiotics was proven by elemental analysis, UV spectrophotometry, and HPLC. The cytocompatibility of the materials was verified in vitro according to ISO 10993-5. The cell adhesion and proliferation were assessed after 2, 7, 14, and 21 days using the CCK-8 metabolic assay, fluorescence, and scanning electron microscopy. The tested nanofiber materials supported cell growth. Antibacterial tests were performed to confirm the release of gentamicin sulfate, and its antibacterial properties were proven toward Staphylococcus gallinarum and Escherichia coli bacteria. The effect of ethylene oxide sterilization was also studied. The sterilized nanofibrous layers are cytocompatible while antibacterial and therefore suitable for medical applications.

Influence of PLGA End Groups on the Release Profile of Dexamethasone from Ocular Implants

The present study deals with the development of dexamethasone (DM)-loaded implants using ester end-capped Resomer RG 502 poly(lactic acid-co-glycolic acid) (PLGA) (502), acid end-capped Resomer RG 502H PLGA (502H), and a 502H:502 mixture (3:1) via hot melt extrusion (HME). The prepared intravitreal implants (20 and 40% DM loaded in each PLGA) were thoroughly investigated to determine the effect of different end-capped PLGA and drug loading on the long-term release profile of DM. The implants were characterized for solid-state active pharmaceutical ingredient (APIs) using DSC and SWAXS, water uptake during stability study, the crystal size of API in the implant matrix using hot-stage polarized light microscopy, and in vitro release profile. The kinetics of PLGA release was thoroughly investigated using quantitative ¹H NMR spectroscopy. The polymorph of DM crystal was found to remain unchanged after the extrusion and stability study. However, around 3 times reduction in API particle size was observed after the HME process. The morphology and content uniformity of the RT-stored samples were found to be comparable to the initial implant samples. Interestingly, the samples (mainly 502H) stored at 40 °C and 75% RH for 30 d demonstrated marked deformation and a change in content uniformity. The rate of DM release was higher in the case of 502H samples with a higher drug loading (40% w/w). Furthermore, a simple digital in vitro DM release profile derived for the formulation containing a 3:1 ratio of 502H and 502 was comparable with the experimental release profile of the respective polymer mixture formulation. The temporal development of pores and/or voids in the course of drug dissolution, evaluated using μCT, was found to be a precursor for the PLGA release. Overall, the release profile of DM was found to be dependent on the PLGA type (independent of subtle changes in the formulation mass and diameter). However, the extent of release was found to be dependent on DM loading. Thus, the present investigation led to a thorough understanding of the physicochemical properties of different end-capped PLGAs and the underlying formulation microstructure on the release profile of a crystalline water-insoluble drug, DM, from the PLGA-based implant.

The Role of the Mechanical, Structural, and Thermal Properties of Poly(l-lactide-co-glycolide-co-trimethylene carbonate) in the Development of Rods with Aripiprazole

In this work, we aimed to determine the role of the mechanical, structural, and thermal properties of poly(l-lactide-co-glycolide-co-trimethylene carbonate) (P(l-LA:GA:TMC)) with shape memory in the formulation of implantable and biodegradable rods with aripiprazole (ARP). Hot melt extrusion (HME) and electron beam (EB) irradiation were applied in the formulation process of blank rods and rods with ARP. Rod degradation was carried out in a PBS solution. HPLC; NMR; DSC; compression and tensile tests; molecular weight (M_n); water uptake (WU); and weight loss (WL) analyses; and SEM were used in this study. HME and EB irradiation did not influence the structure of ARP. The mechanical tests indicated that the rods may be safely implanted using a pre-filled syringe. During degradation, no unfavorable changes in terpolymer content were observed. A decrease in the glass transition temperature and the M_n, and an increase in the WU and the WL were revealed. The loading of ARP and EB irradiation induced earlier pore formation and more intense WU and WL changes. ARP was released in a tri-phasic model with the lag phase; therefore, the proposed formulation may be administered as a delayed-release system. EB irradiation was found to accelerate ARP release.

Influence of electron beam irradiation on extracellular matrix of the human allogeneic skin grafts

The nonviable allogeneic human skin grafts might be considered as the most suitable skin substitutes in the treatment of extensive and deep burns. However, in accordance to biological security such grafts require the final sterilization prior to clinical application. The aim of the study was to verify the influence of electron beam irradiation of three selected doses: 18, 25, and 35 kGy on the extracellular matrix of human skin. Prior to sterilization, the microbiological tests were conducted and revealed contamination in all examined cases. Individual groups were subjected to single electron beam radiation sterilization at proposed doses and then subjected to microbiological tests again. The results of microbiological testing performed for all irradiation doses used were negative. Only in the control group was a growth of microorganisms observed. The FTIR spectrometry tests were conducted followed by the histological evaluation and mechanical tests. In addition, cost analysis of radiation sterilization of individual doses was performed. The results of spectroscopic analysis, mechanical tests, and histological staining showed no significant changes in composition and characteristics of tested tissues after their irradiation, in comparison to control samples. The cost analysis has shown that irradiation with 18 kGy is the most cost-effective and 35 kGy is the least favorable. However, according to biological risk reduction, the recommended sterilization dose is 35 kGy, despite the higher price compared to the other doses tested.

In vitro and in vivo evaluation of gentamicin sulphate-loaded PLGA nanoparticle-based film for the treatment of surgical site infection

The study focuses on the in vitro and in vivo evaluation of the developed gentamicin sulphate (GS)-loaded poly lactic-co-glycolic acid (PLGA) nanoparticle (PNP)-based pullulan film (PNP-F). Sterilization being an essential pre-requisite for the dosage form was carried out using ethylene oxide. Post-sterilization, PNP-F was evaluated for mechanical properties, percentage drug loading, antimicrobial effectiveness study, test for sterility and in vitro dissolution study using Strat-M® membrane. In vitro dissolution study revealed that GS gradually released from PNP-F and the highest cumulative percentage drug release was found to be 86.76 ± 0.03% at 192 h. Wound healing assay was performed to study the effect of PNP-F over migratory potential of dermal fibroblast cells (NIH-3T3) in the presence of micro-organisms, Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA). PNP-F inhibited the growth of PA and SA, allowing the growth of fibroblast cells indicating its suitability for application. In vivo study of surgical site was performed by superficial incision model in Wistar rats. Measurement of in vivo incision healing confirmed faster wound healing in the incision which received PNP-F compared to marketed cream containing GS. Graphical abstract.

Dexamethasone PLGA Microspheres for Sub-Tenon Administration: Influence of Sterilization and Tolerance Studies

Many diseases affecting the posterior segment of the eye require repeated intravitreal injections with corticosteroids in chronic treatments. The periocular administration is a less invasive route attracting considerable attention for long-term therapies. In the present work, dexamethasone-loaded poly(lactic-co-glycolic) acid (PLGA) microspheres (Dx-MS) were prepared using the oil-in-water (O/W) emulsion solvent evaporation technique. MS were characterized in terms of mean particle size and particle size distribution, external morphology, polymer integrity, drug content, and in vitro release profiles. MS were sterilized by gamma irradiation (25 kGy), and dexamethasone release profiles from sterilized and non-sterilized microspheres were compared by means of the similarity factor (f₂). The mechanism of drug release before and after irradiation exposure of Dx-MS was identified using appropriate mathematical models. Dexamethasone release was sustained in vitro for 9 weeks. The evaluation of the in vivo tolerance was carried out in rabbit eyes, which received a sub-Tenon injection of 5 mg of sterilized Dx-MS (20–53 µm size containing 165.6 ± 3.6 µg Dx/mg MS) equivalent to 828 µg of Dx. No detectable increase in intraocular pressure was reported, and clinical and histological analysis of the ocular tissues showed no adverse events up to 6 weeks after the administration. According to the data presented in this work, the sub-Tenon administration of Dx-MS could be a promising alternative to successive intravitreal injections for the treatment of chronic diseases of the back of the eye.

Potential Roles of the Glass Transition Temperature of PLGA Microparticles in Drug Release Kinetics

Poly(lactic-co-glycolic acid) (PLGA) has been used for long-acting injectable drug delivery systems for more than 30 years. The factors affecting the properties of PLGA formulations are still not clearly understood. The drug release kinetics of PLGA microparticles are influenced by many parameters associated with the formulation composition, manufacturing process, and post-treatments. Since the drug release kinetics have not been explainable using the measurable properties, formulating PLGA microparticles with desired drug release kinetics has been extremely difficult. Of the various properties, the glass transition temperature, T_g, of PLGA formulations is able to explain various aspects of drug release kinetics. This allows examination of parameters that affect the T_g of PLGA formulations, and thus, affecting the drug release kinetics. The impacts of the terminal sterilization on the T_g and drug release kinetics were also examined. The analysis of drug release kinetics in relation to the T_g of PLGA formulations provides a basis for further understanding of the factors controlling drug release.

Novel biodegradable Round Window Disks for inner ear delivery of dexamethasone

Drug delivery to the inner ear is an important and very challenging field. The cochlea is protected by several barriers that need to be overcome in the drug delivery process. Local drug delivery can avoid undesirable side effects arising from systemic drug delivery. We developed a biodegradable dexamethasone-loaded Round Window (RW) Disk based on poly(D,L-lactic-co-glycolic acid) (PLGA) for local drug therapy to the inner ear by RW membrane administration by a film-casting method. The optimal drying time was characterized by thermogravimetric analysis and differential scanning calorimetry. In addition, the mass and polymer degradation over time of drug release was measured in vitro showing a total mass loss of 70% after 3 weeks. Dexamethasone release was determined by a RW model setup using a polyethylene terephthalate membrane. We achieved a controlled release over 52 days. Ex vivo implantation of a RW Disk onto a guinea pig RW membrane indicated well-fitting properties of the drug delivery device leading to a close surface contact with the membrane and the successful proof of concept. The developed RW Disks could be new and promising drug delivery device to achieve effective local drug delivery to the inner ear for an extended time.

Nanopharmaceuticals for Eye Administration: Sterilization, Depyrogenation and Clinical Applications

Simple Summary

Nanopharmaceuticals have revolutionized the way ophthalmic drugs are administered to overcome ocular delivery barriers and improve drug bioavailability. The design and production of an efficient ocular drug delivery system still remain a challenge. In this review, we discuss the sterilization and depyrogenation methods, commonly used for ophthalmic nanopharmaceuticals, and their clinical applications.

Abstract

As an immune-privileged target organ, the eyes have important superficial and internal barriers, protecting them from physical and chemical damage from exogenous and/or endogenous origins that would cause injury to visual acuity or even vision loss. These anatomic, physiological and histologic barriers are thus a challenge for drug access and entry into the eye. Novel therapeutic concepts are highly desirable for eye treatment. The design of an efficient ocular drug delivery system still remains a challenge. Although nanotechnology may offer the ability to detect and treat eye diseases, successful treatment approaches are still in demand. The growing interest in nanopharmaceuticals offers the opportunity to improve ophthalmic treatments. Besides their size, which needs to be critically monitored, nanopharmaceuticals for ophthalmic applications have to be produced under sterilized conditions. In this work, we have revised the different sterilization and depyrogenation methods for ophthalmic nanopharmaceuticals with their merits and drawbacks. The paper also describes clinical sterilization of drugs and the outcomes of inappropriate practices, while recent applications of nanopharmaceuticals for ocular drug delivery are also addressed.

Electrospun Nimodipine-loaded fibers for nerve regeneration: Development and in vitro performance

Nimodipine is a 1,4-Dihydropyridine type calcium antagonist routinely used to control blood pressure and reduce the risk of secondary ischemia after aneurismal subarachnoid hemorrhage. Additionally, Nimodipine has unique neuroprotective properties. With respect to brain related applications, the full potential of the desired local effect can often not be realized after systemic administration due to systemic side effects. Therefore, it was our aim to develop a biodegradable drug delivery system for the local controlled release of the drug inside the brain. As a suitable and biodegradable system we successfully electrospun PLGA fibers containing 1 and 10% drug. The results of DSC and X-Ray diffractometry measurements indicate that Nimodipine was incorporated in the polymer matrix in the amorphous state. No drug recrystallization was detected for up to 6 months. Electron-beam sterilization was tried but reduced the drug content of the fiber mats considerably. A sustained drug release over 4-8 days was observed, highly depended on release conditions. The Nimodipine fiber mats exhibited no cell toxicity. In contrast, the electrospun fibers were able to significantly reduce cell death in in vitro cell models of oxidative, osmotic and heat-induced cell stress in Schwann cells, neuronal cells as well as immortalized and primary astrocytes. Therefore, electrospun Nimodipine loaded PLGA fibers represent a promising drug delivery system to realize the druǵs benefits for its intracranial use.

Nonspherical Nanoparticle Shape Stability Is Affected by Complex Manufacturing Aspects: Its Implications for Drug Delivery and Targeting

The shape of nanoparticles is known recently as an important design parameter influencing considerably the fate of nanoparticles with and in biological systems. Several manufacturing techniques to generate nonspherical nanoparticles as well as studies on in vitro and in vivo effects thereof have been described. However, nonspherical nanoparticle shape stability in physiological-related conditions and the impact of formulation parameters on nonspherical nanoparticle resistance still need to be investigated. To address these issues, different nanoparticle fabrication methods using biodegradable polymers are explored to produce nonspherical nanoparticles via the prevailing film-stretching method. In addition, systematic comparisons to other nanoparticle systems prepared by different manufacturing techniques and less biodegradable materials (but still commonly utilized for drug delivery and targeting) are conducted. The study evinces that the strong interplay from multiple nanoparticle properties (i.e., internal structure, Young's modulus, surface roughness, liquefaction temperature [glass transition (T_g ) or melting (T_m )], porosity, and surface hydrophobicity) is present. It is not possible to predict the nonsphericity longevity by merely one or two factor(s). The most influential features in preserving the nonsphericity of nanoparticles are existence of internal structure and low surface hydrophobicity (i.e., surface-free energy (SFE) > ≈55 mN m^-1 , material-water interfacial tension <6 mN m^-1 ), especially if the nanoparticles are soft (<1 GPa), rough (R_rms > 10 nm), porous (>1 m² g^-1 ), and in possession of low bulk liquefaction temperature (<100 °C). Interestingly, low surface hydrophobicity of nanoparticles can be obtained indirectly by the significant presence of residual stabilizers. Therefore, it is strongly suggested that nonsphericity of particle systems is highly dependent on surface chemistry but cannot be appraised separately from other factors. These results and reviews allot valuable guidelines for the design and manufacturing of nonspherical nanoparticles having adequate shape stability, thereby appropriate with their usage purposes. Furthermore, they can assist in understanding and explaining the possible mechanisms of nonspherical nanoparticles effectivity loss and distinctive material behavior at the nanoscale.

Sterilization of hydrogels for biomedical applications: A review

Despite the beneficial properties and outstanding potential of hydrogels for biomedical applications, several unmet challenges must be overcome, especially regarding to their known sensitivity to conventional sterilization methods. It is crucial for any biomaterial to withstand an efficient sterilization to obtain approval from regulatory organizations and to safely proceed to clinical trials. Sterility assurance minimizes the incidence of medical device-related infections, which still constitute a major concern in health care. In this review, we provide a detailed and comprehensive description of the published work from the past decade regarding the effects of sterilization on different types of hydrogels for biomedical applications. Advances in hydrogel production methods with simultaneous sterilization are also reported. Terminal sterilization methods can induce negative or positive effects on several material properties (e.g., aspect, size, color, chemical structure, mechanical integrity, and biocompatibility). Due to the complexity of factors involved (e.g., material properties, drug stability, sterilization conditions, and parameters), it is important to note the virtual impossibility of predicting the outcome of sterilization methods to determine a set of universal rules. Each system requires case-by-case testing to select the most suitable, effective method that allows for the main properties to remain unaltered. The impact of sterilization methods on the intrinsic properties of these systems is understudied, and further research is needed. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2472-2492, 2018.

Microdevice Platform for In Vitro Nervous System and Its Disease Model

The development of precise microdevices can be applied to the reconstruction of in vitro human microenvironmental systems with biomimetic physiological conditions that have highly tunable spatial and temporal features. Organ-on-a-chip can emulate human physiological functions, particularly at the organ level, as well as its specific roles in the body. Due to the complexity of the structure of the central nervous system and its intercellular interaction, there remains an urgent need for the development of human brain or nervous system models. Thus, various microdevice models have been proposed to mimic actual human brain physiology, which can be categorized as nervous system-on-a-chip. Nervous system-on-a-chip platforms can prove to be promising technologies, through the application of their biomimetic features to the etiology of neurodegenerative diseases. This article reviews the microdevices for nervous system-on-a-chip platform incorporated with neurobiology and microtechnology, including microfluidic designs that are biomimetic to the entire nervous system. The emulation of both neurodegenerative disorders and neural stem cell behavior patterns in micro-platforms is also provided, which can be used as a basis to construct nervous system-on-a-chip.

The impact of storage conditions upon gentamicin coated antimicrobial implants

A systematic approach was developed to investigate the stability of gentamicin sulfate (GS) and GS/poly (lactic-co-glycolic acid) (PLGA) coatings on hydroxyapatite surfaces. The influence of environmental factors (light, humidity, oxidation and heat) upon degradation of the drug in the coatings was investigated using liquid chromatography with evaporative light scattering detection and mass spectrometry. GS coated rods were found to be stable across the range of environments assessed, with only an oxidizing atmosphere resulting in significant changes to the gentamicin composition. In contrast, rods coated with GS/PLGA were more sensitive to storage conditions with compositional changes being detected after storage at 60 °C, 75% relative humidity or exposure to light. The effect of γ-irradiation on the coated rods was also investigated and found to have no significant effect. Finally, liquid chromatography-mass spectrometry analysis revealed that known gentamines C1, C1a and C2 were the major degradants formed. Forced degradation of gentamicin coatings did not produce any unexpected degradants or impurities.

The effect of steam sterilization on recombinant spider silk particles

In this work, the recombinant spider silk protein eADF4(C16) was used to fabricate particles in the submicron range using a micromixing method. Furthermore, particles in the micrometer range were produced using an ultrasonic atomizer system. Both particle species were manufactured by an all-aqueous process. The submicroparticles were 332 nm in average diameter, whereas 6.70 μm was the median size of the microparticles. Both particle groups showed a spherical shape and exhibited high β-sheet content in secondary structure. Submicro- and microparticles were subsequently steam sterilized and investigated with respect to particle size, secondary structure and thermal stability. Sterilization temperature and time were increased to assess the thermal stability of eADF4(C16) particles. Actually, particles remained stable and their properties did not change even after autoclaving at 134°C. Both, the untreated and the autoclaved submicroparticles showed no overt cytotoxicity on human dermal fibroblasts after incubation for 72 h. The eADF4(C16) particles were already loaded with proteins and small molecules in previous studies. With that, we can provide a highly promising parenteral drug delivery system based on a defined polypeptide carrier, manufactured with an all-aqueous process and being fully sterilizable.

Thymopentin nanoparticles engineered with high loading efficiency, improved pharmacokinetic properties, and enhanced immunostimulating effect using soybean phospholipid and PHBHHx polymer

Formulation of protein and peptide drugs with sustained release properties is crucial to enhance their therapeutic effect and minimize administration frequency. In this study, immunomodulating polymeric systems were designed by manufacturing PHBHHx nanoparticles (NPs) containing thymopentin (TP5). The release profile of the drug was studied over a period of 7 days. The PHBHHx NPs containing TP5-phospholipid (PLC) complex (TP5-PLC) displayed a spherical shape with a mean size, zeta potential, and encapsulation efficiency of 238.9 nm, -32.0 mV, and 72.81%, respectively. The cytotoxicity results showed the PHBHHx NPs had a relatively low toxicity in vitro. TP5 entrapped in the NPs could hardly release in vitro, while the NPs had longer than 7 days release duration after a single subcutaneous injection in Wistar rats. The immunodepression rat model was built to evaluate the immunomodulating effects of TP5-PLC-NPs in vivo. The results of T-lymphocyte subsets (CD3(+), CD4(+), CD8(+), and CD4(+)/CD8(+) ratio) analysis and superoxide dismutase (SOD) values suggested that TP5-PLC-NPs had stronger immunoregulation effects than TP5 solution. In conclusion, an applicable approach to markedly enhancing the loading of a water-soluble peptide into a hydrophobic polymer matrix has been introduced. Thus, TP5-PLC-NPs are promising nanomedicine systems for sustained release effects of TP5.

Radiation sterilization of new drug delivery systems

Radiation sterilization has now become a commonly used method for sterilization of several active ingredients in drugs or drug delivery systems containing these substances. In this context, many applications have been performed on the human products that are required to be sterile, as well as on pharmaceutical products prepared to be developed. The new drug delivery systems designed to deliver the medication to the target tissue or organ, such as microspheres, nanospheres, microemulsion, and liposomal systems, have been sterilized by gamma (γ) and beta (β) rays, and more recently, by e-beam sterilization. In this review, the sterilization of new drug delivery systems was discussed other than conventional drug delivery systems by γ irradiation.

Challenges facing sterilization and depyrogenation of nanoparticles: effects on structural stability and biomedical applications

This review outlines and compares techniques that are currently available for the sterilization of nanoparticles and addresses the topic of endotoxin contamination. Several techniques are available for the removal of microbial contamination from nanoparticles developed for use in nanomedicine applications. These techniques include filtration, autoclaving and irradiation, as well as formaldehyde, ethylene oxide and gas plasma treatments. Of these sterilization methodologies, filtration may potentially remove microbial contamination without altering the physicochemical properties of the carrier nanoparticles, nor affecting their toxicity and functionality. However, no single process may be applied to all nanoparticle preparations and, therefore, it is recommended that each nanoparticle-drug system be validated on a case-by-case basis. From the clinical editor: This comprehensive review covers the currently available methods for removal of microbial contaminations from nanoparticles for nanomedicine applications. The review highlights the pros and cons of each available method. Authors conclude that there is no single best method and recommend a customized approach for each nanoparticle system.

Preservation of biological activity of glial cell line-derived neurotrophic factor (GDNF) after microencapsulation and sterilization by gamma irradiation

A main issue in controlled delivery of biotechnological products from injectable biodegradable microspheres is to preserve their integrity and functional activity after the microencapsulation process and final sterilization. The present experimental work tested different technological approaches to maintain the biological activity of an encapsulated biotechnological product within PLGA [poly (lactic-co-glycolic acid)] microspheres (MS) after their sterilization by gamma irradiation. GDNF (glial cell line-derived neurotrophic factor), useful in the treatment of several neurodegenerative diseases, was chosen as a labile model protein. In the particular case of optic nerve degeneration, GDNF has been demonstrated to improve the damaged retinal ganglion cells (RGC) survival. GDNF was encapsulated in its molecular state by the water-in-oil-in-water (W/O/W) technique or as solid according to the solid-in-oil-in-water (S/O/W) method. Based on the S/O/W technique, GDNF was included in the PLGA microspheres alone (S/O/W 1) or in combination with an antioxidant (vitamin E, Vit E) (S/O/W 2). Microspheres were sterilized by gamma-irradiation (dose of 25 kGy) at room and low (-78 °C) temperatures. Functional activity of GDNF released from the different microspheres was evaluated both before and after sterilization in their potential target cells (retinal cells). Although none of the systems proposed achieved with the goal of totally retain the structural stability of the GDNF-dimer, the protein released from the S/O/W 2 microspheres was clearly the most biologically active, showing significantly less retinal cell death than that released from either W/O/W or S/O/W 1 particles, even in low amounts of the neurotrophic factor. According to the results presented in this work, the biological activity of biotechnological products after microencapsulation and sterilization can be further preserved by the inclusion of the active molecule in its solid state in combination with antioxidants and using low temperature (-78 °C) during gamma irradiation exposure.

Inactivation of microorganisms within collagen gel biomatrices using pulsed electric field treatment

Pulsed electric field (PEF) treatment was examined as a potential decontamination method for tissue engineering biomatrices by determining the susceptibility of a range of microorganisms whilst within a collagen gel. High intensity pulsed electric fields were applied to collagen gel biomatrices containing either Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, Candida albicans, Saccharomyces cerevisiae or the spores of Aspergillus niger. The results established varying degrees of microbial PEF susceptibility. When high initial cell densities (10(6)-10(7) CFU ml(-1)) were PEF treated with 100 pulses at 45 kV cm(-1), the greatest log reduction was achieved with S. cerevisiae (~6.5 log(10) CFU ml(-1)) and the lowest reduction achieved with S. epidermidis (~0.5 log(10) CFU ml(-1)). The results demonstrate that inactivation is influenced by the intrinsic properties of the microorganism treated. Further investigations are required to optimise the microbial inactivation kinetics associated with PEF treatment of collagen gel biomatrices.

Developing biodegradable scaffolds for tissue engineering of the urethra

OBJECTIVE

To develop a synthetic biodegradable alternative to using human allodermis for the production of tissue-engineered buccal mucosa for substitution urethroplasty, looking specifically at issues of sterilization and cell-seeding protocols and, comparing the results to native buccal mucosa.

MATERIAL AND METHODS

Three methods of sterilization, peracetic acid (PAA), γ-irradiation and ethanol, were evaluated for their effects on a biodegradable electrospun scaffold of polylactide-co-glycolide (PLGA, 85:15), to identify a sterilization method with minimal adverse effects on the scaffolds. Two protocols for seeding oral cells on the scaffold were compared, co-culture of fibroblasts and keratinocytes on the scaffolds for 14 days, and seeding fibroblasts for 5 days then adding keratinocytes for a further 10 days. Cell viability and proliferation on the scaffolds, scaffold contraction and mechanical properties of the scaffolds with and without cells were examined.

RESULTS

γ-irradiation and PAA sterilized scaffolds remained sterile for >3 months when incubated in antibiotic-free culture medium, while ethanol sterilized and unsterilized samples became infected within 2-14 days. All scaffolds showed extensive contraction (up to 50% over 14 days) irrespective of the method of sterilization or the presence of cells. All methods of sterilization, particularly ethanol, reduced the tensile strength of the scaffolds. The addition of cells tended to further reduce mechanical properties but increased elasticity. The cell-seeding protocol of adding fibroblasts for 5 days followed by keratinocytes for 10 days was the most promising, achieving a mean (sem) ultimate tensile stress of 1.20 (0.24) × 10⁵ N/m² compared to 3.77 (1.05) × 10⁵ N/m² for native buccal mucosa, and a Young's modulus of 2.40 (0.25) MPa, compared to 0.73 (0.09) MPa for the native buccal mucosa.

CONCLUSION

This study adds to our understanding of how sterilization and cell seeding affect the physical properties of scaffolds. Both PAA and γ-irradiation appear to be suitable methods for sterilizing PLGA scaffolds, although both reduce the tensile properties of the scaffolds. Cells grow well on the sterilized scaffolds, and with our current protocol produce constructs which have ≈ 30% of the mechanical strength and elasticity of the native buccal mucosa. We conclude that sterilized PLGA 85:15 is a promising material for producing tissue-engineered buccal mucosa.

Design of methylprednisolone biodegradable microspheres intended for intra-articular administration

This study aimed to design methyprednisolone (MP)-loaded poly(D,L lactide-co-glycolide) (PLGA) microspheres (MS) intended for intra-articular administration. MP was encapsulated in four different types of PLGA by using an S/O/W technique. The effects of beta-irradiation at the dose of 25 kGy were evaluated on the chemical and physicochemical properties of MS and the drug release profiles. The S/O/W technique with hydroxypropylmethylcellulose (HPMC) as surfactant allowed obtaining MS in the tolerability size (7-50 microm) for intra-articular administration. The MP encapsulation efficiency ranged 56-60%. HPMC traces were evidenced in the loaded and placebo MS by attenuated total reflectance Fourier transform infrared spectroscopy. MS made of the capped PLGA DL5050 2M (MS 2M) and uncapped PLGA DL5050 3A (MS 3A) prolonged the release of MP over a 2- to 3-month period with a triphasic (burst release-dormant period-second release pulse) and biphasic release pattern, respectively. The beta-irradiation did not significantly alter the morphology, chemical, and physicochemical properties of MS. The only variation was evidenced in the drug release for MS 2M in term of shorting of the dormant period. The minimal variations in the properties of irradiated PLGA MS, which are in disagreement with literature data, may be attributed to a radioprotecting effect exerted by HPMC.