Indirect Contact Tests Research Articles

Incorporating an artificially synthesized fluoride complex into urethane-acrylate-based 3D printing resin: Effects on mechanical properties, cytotoxicity, antimicrobial actions, and its long-term fluoride-releasing properties

ObjectivesTo synthesize a 3D printing resin with antibacterial and long-term fluoride-releasing properties. Methods(4,4-Bis-4-[2‑hydroxy-3-(2-methacryloyloxy)propoxy]-phenyl-pentanol-amine)-N,N-diacetic acid zirconium (IV) fluoride complex was synthesized from 4,4-bis-(4-hydroxyphenyl)-pentanoic acid and monitored using proton nuclear magnetic resonance spectroscopy. The synthesized complex was incorporated into a urethane-acrylate-based (UA) resin at 5 wt% and 10 wt% (5F-UA and 10F-UA groups, respectively). The UA resin without the synthesized complex was considered as the control group. All groups were 3D printed using a DLP printer, followed by 10 min of washing and 20 min of curing. Surface characteristics were observed using scanning electron microscopy. The mechanical properties were assessed by measuring its flexural strength and Vickers hardness. The antibacterial property was investigated with direct and indirect contact tests and a WST-8 metabolic activity assay. The suspension was fully mixed and diluted for counting the number of colony-forming units. The cell viability test was performed using a cell proliferation assay. The amount of fluoride released was measured daily for 28 days using ion chromatography. One-way analysis of variance was performed for statistical analyses using SPSS software. ResultsThe amount of fluoride released increased with the concentration of fluoride complex in the resin. The fluoride ions were constantly released at a low concentration from the 3D printed specimens (5F-UA: around 0.13 ppm daily; 10F-UA: around 0.22 ppm daily). The antibacterial efficacy was acceptable in both the 5F-UA and 10F-UA groups, and higher in the latter. No cytotoxicity of the resin was detected. The mechanical properties were significantly influenced by the addition of the fluoride-releasing complex. ConclusionsThe present 3D printing UA resin incorporating a fluoride complex effectively inhibited the growth of S. mutans and demonstrated the ability to slowly release fluoride over an extended period of time. Clinical significanceThis study provided informative composition of a fluoride-releasing UA-based 3D printing resin, ideal for dental applications such as crowns, bridges, removable partial dentures, and orthodontic appliances, which can benefit from sustained fluoride release and antimicrobial properties. Further modifications to the resin composition can be easily achieved to enhance the resin qualities.

Titanium-doped phosphate glasses containing zinc and strontium applied in bone regeneration

Phosphate bioactive glass has been studied for its advanced biodegradability and active ion release capability. Our previous research found that phosphate glass containing (P2O5)–(Na2O)–(TiO2)–(CaO)–(SrO) or (ZnO) showed good biocompatibility with MG63 and hMSCs. This study further investigated the application of 5 mol% zinc oxide or 17.5 mol% strontium oxide in titanium-doped phosphate glass for bone tissue engineering. Ti-Ca-Na-Phosphate glasses, incorporating 5% zinc oxide or 17.5% strontium oxide, were made with melting quenching technology. The pre-osteoblast cell line MC3T3-E1 was cultured for indirect contact tests with graded diluted phosphate glass extractions and for direct contact tests by seeding cells on glass disks. The cell viability and cytotoxicity were analysed in vitro over 7 days. In vivo studies utilized the tibial defect model with or without glass implants. The micro-CT analysis was performed after surgery and then at 2, 6, and 12 weeks. Extractions from both zinc and strontium phosphate glasses showed no negative impact on MC3T3-E1 cell viability. Notably, non-diluted Zn-Ti-Ca-Na-phosphate glass extracts significantly increased cell viability by 116.8% (P < 0.01). Furthermore, MC3T3-E1 cells cultured with phosphate glass disks exhibited no increase in LDH release compared with the control group. Micro-CT images revealed that, over 12 weeks, both zinc-doped and strontium-doped phosphate glasses demonstrated good bone incorporation and longevity compared to the no-implant control. Titanium-doped phosphate glasses containing 5 mol% zinc oxide, or 17.5 mol% strontium oxide have promising application potential for bone regeneration research.Graphical

Comparative Study on Bioactive Filler/Biopolymer Scaffolds for Potential Application in Supporting Bone Tissue Regeneration

The combination of biopolymers and bioactive inorganic particles for bone tissue regeneration has been investigated in the last decades. However, several studies report discordant results on the specific synergistic effect of the compounds. A comparative study on porous scaffolds obtained by the combination of the most promising biopolymers and bioactive inorganic particles is herein reported. Specifically, porous scaffolds have been fabricated by the Thermally Induced Phase Separation method using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(lactic acid) (PLA), and poly(caprolactone) (PCL) compounded with hydroxyapatite (HAp), calcium silicate (CS), or a Mg- and Sr-rich bioglass (BG) with a nominal composition of 2.3% Na2O, 2.3% K2O, 25.6% CaO, 10.0% MgO, 10.0% SrO, 2.6% P2O5, and 47.2% SiO2. Morphological analyses revealed the formation of highly interconnected and aligned open pores. Both thermal investigations and compressive tests highlight the close similarity between PLA- and PHBV-based scaffolds in terms of the amorphous structure and stiffness when the fillers are added. On the other hand, the addition of amorphous BG in semicrystalline PCL shows a decrease of the crystallinity degree of the polymer and a consequent decrease of the compressive modulus. Preliminary in vitro investigations (direct and indirect contact tests) carried out on the composite systems revealed that all the prepared materials provide an appropriate environment for NIH 3T3 cell adhesion and proliferation, showing a total lack of cytotoxicity. The addition of all the inorganic fillers has an overall positive effect on cell proliferation, viability (Neutral Red uptake), and metabolic activity (MTT test). Interestingly, this effect is particularly evident whenever BG is added. The combination of both amorphous BGs with amorphous polymers, such as PLA and PHBV, seems to be responsible for creating the best microenvironmental cue for NIH 3T3 cell attachment and proliferation.

Cytotoxicity of universal dental adhesive systems: Assessment in vitro assays on human gingival fibroblasts

Universal adhesives are the most important innovation in restorative dentistry. They are composed of different monomers, solvents and fillers. The potential cytotoxic effect of these materials is an important scientific aspect in recent literature. The aim of this study was to determine, using different in vitro techniques, the cytotoxicity evaluation of seven universal enamel-dental adhesives on human gingival fibroblasts. For this purpose, seven universal dental enamel adhesives have been evaluated by in vitro cytotoxicity tests using direct contact tests (an unpolymerized and a polymerized method) and an indirect contact test: preparation of extracts. The polymerized method showed a cytotoxicity range from 36% (G-PremioBond, GPB) to 79% (FuturaBond M+, FB). With the unpolymerized direct methods the range was from 4% (Prime&Bond Active, PBA) to 40% (Ibond Universal, IB) for undiluted adhesives; generally passing to the major dilutions the test showed a strong inhibitory activity by all the adhesives. Whereas with the indirect method by diluting the extracts of all dental adhesives the cell viability increased. The data obtained from the work has shown a lower cytotoxic effect of Optibond Solo Plus (OB) and Adhesive Universal (AU) with more reliable results with the extracts technique. The choice of reliable in vitro cytotoxic technique could represent, in dental practice, an important aid for clinical procedures in the use of adhesive systems.

SBF assays, direct and indirect cell culture tests to evaluate the biological performance of bioglasses and bioglass-based composites: Three paradigmatic cases

A novel bioglass composition (BGMS10), containing strontium and magnesium and characterized by an ultra-high crystallization temperature, is here employed for the first time to produce different composites with the addition of specific amounts of hydroxyapatite. After an investigation of the samples' bioactivity in vitro in a simulated body fluid solution (SBF) – according to a widely used protocol –, the biocompatibility of the new materials was tested with respect to murine fibroblasts both by direct and indirect tests, in order to evaluate possible cytotoxic effects of the materials' eluates. Although none of the samples were cytotoxic and their bioactivity in SBF increased with the increasing amount of the glass in the composite, thus showing the best performance in the case of pure BGMS10 glass, the findings of the biological investigation did not confirm those arising from the SBF assay. Surprisingly, while the composites with the lowest glass amount showed an enhanced biocompatibility in direct tests, on the contrary their biological responsiveness is typically lower in the indirect ones, based on filtered materials' extracts. This fact could be ascribed to the high release of particulate from the composites, which are more porous than the glassy samples: in fact, such pronounced dissolution may affect both the cell viability and the absorbance readings used in the colorimetric assays. The pure BGMS10 glass showed the best biological response only in the cell proliferation test (which is an indirect contact test), being able to stimulate cell proliferation in particular after 24 h. For these reasons, when considering bioactive glasses and bioglass-based composites, the results of direct cell culture assays should be integrated with those obtained by indirect ones, while the findings regarding the in vitro bioactivity in SBF should be interpreted with great care.

Microwave-assisted synthesis and evaluation of type 1 collagen-apatite composites for dental tissue regeneration.

The aim was to develop an economical and biocompatible collagen-based bioactive composite for tooth regeneration. Acid-soluble collagen was extracted and purified from fish scales. The design was innovated to molecularly tailor the surface charge sites of the nano-apatite providing chemical bonds with the collagen matrix via microwave irradiation technique. The obtained collagen was identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis. The composites were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis/differential scanning calorimetry, and scanning electron microscopy. MC3T3-E1 cell lines were used to assess the biological effects of these materials by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetra zolium bromide (MTT) assay. Indirect contact test was performed by extracting representative elutes in cell culture media and sulforhodamine B analysis was performed. Chorioallantoic membrane assay was conducted to define the new vessels formation behavior. The purity of collagen extracts was determined and showed two α-chains, i.e. the characteristic of type I collagen. Fourier transform infrared spectroscopy showed the characteristic peaks for amide I, I, III, and phosphate for collagen and composites. Scanning electron microscopy images showed three-dimensional mesh of collagen/apatite nano-fibers. Nontoxic behavior of composites was observed and there were graded and dose-related effects on experimental compounds. The angiogenesis and vessels formation behavior were observed in bioactive collagen composite. The obtained composites have potential to be used for tooth structure regeneration.

Antimicrobial and biological activity of leachate from light curable pulp capping materials

ObjectivesCharacterization of a number of pulp capping materials and assessment of the leachate for elemental composition, antimicrobial activity and cell proliferation and expression. MethodologyThree experimental light curable pulp-capping materials, Theracal and Biodentine were characterized by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. The elemental composition of the leachate formed after 24h was assessed by inductively coupled plasma (ICP). The antimicrobial activity of the leachate was determined by the minimum inhibitory concentration (MIC) against multispecies suspensions of Streptococcus mutans ATCC 25175, Streptococcus gordonii ATCC 33478 and Streptococcus sobrinus ATCC 33399. Cell proliferation and cell metabolic function over the material leachate was assessed by an indirect contact test using 3-(4,5 dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. ResultsThe hydration behavior of the test materials varied with Biodentine being the most reactive and releasing the highest amount of calcium ions in solution. All materials tested except the unfilled resin exhibited depletion of phosphate ions from the solution indicating interaction of the materials with the media. Regardless the different material characteristics, there was a similar antimicrobial activity and cellular activity. All the materials exhibited no antimicrobial activity and were initially cytotoxic with cell metabolic function improving after 3days. ConclusionsThe development of light curable tricalcium silicate-based pulp capping materials is important to improve the bonding to the final resin restoration. Testing of both antimicrobial activity and biological behavior is critical for material development. The experimental light curable materials exhibited promising biological properties but require further development to enhance the antimicrobial characteristics.

In vitro evaluation of poly(ethylene glycol)-block-poly(ɛ-caprolactone) methyl ether copolymer coating effects on cells adhesion and proliferation

Understanding and controlling natural and synthetic biointerfaces is known to be the key to a wide variety of application within cell culture and tissue engineering field. As both material characteristics and methods are important in tailoring biointerfaces characteristics, in this work we explore the feasibility of using Matrix Assisted Pulsed Laser Evaporation technique for obtaining synthetic copolymeric biocoatings (i.e. poly(ethylene glycol)-block-poly(ɛ-caprolactone) methyl ether) for evaluating in vitro Vero and MC3T3-E1 pre-osteoblasts cell response. Characterization and evaluation of the coated substrates were carried out using different techniques. The Fourier transform infrared spectroscopy data demonstrated that the main functional groups in the MAPLE-deposited films remained intact. Atomic Force Microscopy images showed the coatings to be continuous, with the surface roughness depending on the deposition parameters. Moreover, the behaviour of the coatings in medium mimicking the pH and temperature of the human body was studied and corelated to degradation. Spectro-ellipsometry (SE) and AFM measurements revealed the degradation trend during immersion time by the changes in coating thickness and roughness. In vitro biocompatibility was studied by indirect contact tests on Vero cells in accordance with ISO 10993-5/2009. The results obtained in terms of cell morphology (phase contrast microscopy) and cytotoxicity (LDH and MTT assays) proved biocompatibility. Furthermore, direct contact assays on MC3T3-E1 pre-osteoblasts demonstrated the capacity of all analyzed specimens to support cell adhesion, normal cellular morphology and growth.

A biocompatibility study of injectable poly(caprolactone-trifumarate) for use as a bone substitute material

The need for bone graft alternatives has led to the development of numerous bone graft substitutes. Here, the authors have synthesized a biodegradable poly(caprolactone-trifumarate) (PCLTF) polymer solution that could be injected into any bony defect. This polymer solution was synthesized using polycaprolactone-triol and fumaryl chloride (FCl). PCLTF is a multiple-branching, unsaturated and cross-linkable in situ material. The surface microstructure of PCLTF was investigated using a field emission scanning electron microscope. The incorporation of double bonds originating from FCl into the poly(caprolactone) backbone was confirmed in the Fourier transform infrared spectra. The in vitro cytotoxic effects of PCLTF, its leachable extracts and degradation products were evaluated in direct and indirect contact tests against human oral fibroblasts. Cell viability was evaluated using the microculture tetrazolium assay and cytotoxicity evaluations of PCLTF were tested in accordance with ISO 10993-5 standards. The results showed that there was evidence of reasonable cell growth, good cell viability and intact cell morphology after exposure to PCLTF, its extracts and degradation products. There was no evidence of critical cytotoxic effects.

Study of the in vitro cytotoxicity testing of medical devices.

The cytotoxicity test is one of the biological evaluation and screening tests that use tissue cells in vitro to observe the cell growth, reproduction and morphological effects by medical devices. Cytotoxicity is preferred as a pilot project test and an important indicator for toxicity evaluation of medical devices as it is simple, fast, has a high sensitivity and can save animals from toxicity. Three types of cytotoxicity test are stated in the International Organization for Standardization 109993-5: Extract, direct contact and indirect contact tests. The xCELLigence real-time cell analysis system shows a significant potential in regards to cytotoxicity in recent years. The present review provides a brief insight into the in vitro cytotoxicity testing of medical devices.

Preliminary In Vitro Assessment of Stem Cell Compatibility with Cross-Linked Poly(ε-caprolactone urethane) Scaffolds Designed through High Internal Phase Emulsions.

By using a high internal phase emulsion process, elastomeric poly(ε-caprolactone urethane) (PCLU) scaffolds were designed with pores size ranging from below 150 μm to 1800 μm and a porosity of 86% making them suitable for bone tissue engineering applications. Moreover, the pores appeared to be excellently interconnected, promoting cellularization and future bone ingrowth. This study evaluated the in vitro cytotoxicity of the PCLU scaffolds towards human mesenchymal stem cells (hMSCs) through the evaluation of cell viability and metabolic activity during extract test and indirect contact test at the beginning of the scaffold lifetime. Both tests demonstrated that PCLU scaffolds did not induce any cytotoxic response. Finally, direct interaction of hMSCs and PCLU scaffolds showed that PCLU scaffolds were suitable for supporting the hMSCs adhesion and that the cells were well spread over the pore walls. We conclude that PCLU scaffolds may be a good candidate for bone tissue regeneration applications using hMSCs.

Preparation of core–shell poly(l-lactic) acid-nanocrystalline apatite hollow microspheres for bone repairing applications

In this paper, hybrid inorganic-organic core-shell hollow microspheres, made of poly(L-lactic acid) (PLLA) and biomimetic nano apatites (HA), were prepared from biodegradable and biocompatible substances, suitable for bone tissue applications. Preparation is started from Pickering emulsification, i.e., solid particle-stabilized emulsions in the absence of any molecular surfactant, where solid particles adsorbed to an oil-water interface. Stable oil-in-water emulsions were produced using biomimetic 20 nm sized HA nanocrystals as particulate emulsifier and a dichloromethane (CH(2)Cl(2)) solution of PLLA as oil phase. Hybrid hollow PLLA microspheres at three different HA nanocrystals surface coverage, ranging from 10 to 50 μm, were produced. The resulting materials were completely characterized with spectroscopic, calorimetric and microscopic techniques and the cytocompatibility was established by indirect contact tests with both fibroblasts and osteoblasts and direct contact with these latter. They displayed a high level of cytocompatibility and thus represent promising materials for drug delivery systems, cell carriers and scaffolds for regeneration of bone useful in the treatment of orthopaedic, maxillofacial and dental fields.

Evaluation of cytotoxic effects of six self-etching adhesives with direct and indirect contact tests

This study evaluated the cytotoxicity of self-etching primers/adhesives by direct contact and dentin barrier tests. The three two-step self-etching systems Clearfil SE Bond (CSE), Clearfil Protect Bond (CPB), Prime&Bond NT/NRC (PB) and one-step self-etching systems Reactmer Bond (RB), Clearfil Tri-S Bond (CTS), and Adper Prompt L-Pop (AP) were examined. In direct contact tests, L929 cells were cultured in the presence of diluted solutions (50, 20, 10, and 1%) of primer/conditioner of adhesive systems. For dentin barrier tests, each system was applied onto 0.5 or 1.5 mm thick human dentin assembled in a simple pulp chamber device and incubated for 24 h at 37°C to make the diffusive components contact the L929 cells placed at the bottom of the chamber. The cytotoxic effects were assessed by MTT assay. Cell culture without application of any primers/adhesives served as the control for both tests. One-way ANOVA and Tukey HSD tests were used for statistical analyses. The direct contact tests demonstrated that CSE and CPB were less toxic than the other materials at all dilutions. In the dentin barrier tests, toxic effects of materials were reduced with an increase in thickness of intervening dentin. CSE and CPB showed less cytotoxicity than the other adhesives (p<0.05) when applied to 0.5 mm-thick dentin, and CSE was the least toxic in the 1.5 mm-dentin group (p<0.05). Dentin thickness positively affected biocompatibility of the tested bonding systems. Two-step self-etching systems with HEMA-based primers were more biocompatible than other self-etching adhesives.

Evaluation of in vitro toxic effects of cement dusts: A preliminary study

Cement is widely used for construction and several reports have suggested a potential toxicity of cement dusts although it has never been definitively assessed. To determine the cytotoxic and bioactive effects of cement dusts, cultures of normal rat fibroblasts were exposed to different types of cements and cell growth parameters, apoptosis and the occurrence of DNA damage (both in terms of DNA breaks and oxidative damage) were analyzed. Cells were exposed to cement extracts or cultured in direct contact with cement dusts and the results obtained were compared to cells cultured in fresh medium. A dose-dependent decrease in viable cells was observed with all tested cements. Different results were obtained in the cell-cement direct contact tests compared to the indirect contact tests performed using extracts. Inhibition of cell growth was associated in most cases with an accumulation of cells in the S-phase of the cell-cycle and the appearance of an apoptotic peak. DNA strand breaks, assessed by comet test, and increase in the levels of 8-OHdG, an important marker of DNA oxidative damage, always occurred by incubating cells in the presence of cement extracts or dusts. However, after removal of cement, a rapid damage repair was generally observed with an almost complete recovery within 12 hours. In conclusion, all cements analyzed in this study displayed a limited toxicity in vitro without significant differences amongst them. Overall, the results obtained indicate that cements should be treated as hazardous materials but they do not allow to make accurate predictions regarding the in vivo effects. Further studies are warranted to reach a better understanding of the potential toxic effects of cements, to identify the responsible mechanisms and to evaluate the possibility of modulating and/ or preventing them.

Comparison of different test models for the assessment of cytotoxicity of composite resins

This study compared the use of different test models to assess the cytotoxicity of a dental composite. The cytotoxicity of a composite polymerized using two halogen-based light-curing units (LCUs) (Max LC and Astralis) and two light-emitting diode LCUs (E-light and Freelight) served as the basis of comparison. Disk-shaped specimens (7 mm diameter, 2 mm high) were fabricated using the four different light sources. The specimens were used in several cytotoxicity test models: direct and indirect contact tests as well as an extract test with an established cell line L-929. The cells were stained with neutral red after cell-material contact for 48 h. Neutral red-stained areas (in mm2, for direct and indirect tests) and absorbance readings (for extract tests) were analysed statistically using ANOVA and the Tukey post hoc test, with P < 0.05 considered to be significantly different. Good correlation between direct and indirect contact tests (r = 0.903) was found. The extract test was the least correlated among the three tests. It was found that the E-light + Freelight-cured composite elicited cytotoxicity from the correlated studies. Uncured specimens were most detrimental to the cells in all tests. Our data demonstrated that composite cured with light-emitting diode LCUs were cytotoxic to L-929 cells. Different test models were found to give rise to different findings. Thus, a good cell-material contact method would replicate more closely the physiological situation in vivo. This in turn would give more clinically relevant results.

Tooth slice organ culture and established cell line culture models for cytotoxicity assessment of dental materials

The aim was to compare the use of different cell–material contact test methods with two different biological systems (cell line and tooth slice cultures) for cytotoxicity assessment of dental materials. Cytotoxicity of composites polymerized with two halogen-based and two light-emitting diode (LED) light-curing units (LCUs) served as the basis for comparison. Disk shaped specimens (7×2mm) were fabricated using the four light sources. Composites were tested using L-929 cell line using direct/indirect/extract tests in accordance to standard protocols. Cytotoxicity was assessed using neutral red uptake. Tooth slice organ cultures were also employed to test the dental materials using direct/indirect test methods. Histomorphometric cell counting of intact odontoblasts and pulp fibroblasts and the use of tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays were applied for cytotoxicity evaluation. Discrepancy in result presentation was observed in the different tests used with L-929. Sensitivity levels of the L-929 tests ranked as follows: extract test<direct contact test<indirect contact test. Tooth slice tests confirmed that L-929 direct contact test proved to be the most reliable test among the three. In conclusion, this study highlights the risk involved when relying on a single test method for cytotoxicity assessment. It would be advisable to test different culture models and then proceed using more clinically relevant biological system that stimulate the in vivo situation for confirmation.

Cytotoxicity of resin-based root canal sealer, adseal

The properties of ideal root canal sealers include the ability of sealing the total root canal system and no toxic effects to periradicular tissues. Cytotoxicity test using cell culture is a common screening method for evaluation of the biocompatibility of root canal sealers. The purpose of this study was to investigate the cytotoxic effect of newly developed resin-based sealer (Adseal 1, 2, and 3) comparing with those commercial resin-based sealers (AH26 and AH Plus), ZOE-based sealers (Tubliseal EWT, Pulp Canal Sealer EWT) and calcium hydroxide based sealer (Sealapex). An indirect contact test of cytotoxicity by agar diffusion was performed according to the international standard ISO 10993-5. L929 fibroblast cells were incubated at 37℃ in humidified 5% CO 2-containing air atmosphere. The freshly mixed test materials were inserted into glass rings of internal diameter 5 ㎜ and height 5 ㎜ placed on the agar. After the 24 hrs incubation period, the decolorization zones around the test materials were assessed using an inverted microscope with a calibrated screen. A Decolorization Index was determined for each specimen. Adseal 1, 2, and 3 did not exert any cytotoxic effects, whereas AH26, AH Plus, Tubliseal EWT, Pulp Canal Sealer EWT, and Sealapex

Cytotoxicity study of homopolymers and copolymers of 2-hydroxyethyl methacrylate and some alkyl acrylates for potential use as temporary skin substitutes.

The cytotoxicities of both homopolymers and copolymers of 2-hydroxyethyl methacrylate (HEMA) and various alkyl acrylates (AA) were investigated using cell culture techniques. The particular alkyl acrylates used were methyl acrylate (MA), ethyl acrylate (EA) and butyl acrylate (BA). The AA contents of the polymers studied were in the range of 0-25% by weight. They were synthesized via bulk polymerization in the form of thin sheets of 0.5+/-0.1 mm thickness. After sterilization using ethylene oxide gas, cytotoxicity tests, including both direct and indirect contact tests, were performed using cell lines of L929 and normal human dermal fibroblasts. The results showed that P(HEMA-co-EA) with EA contents of 15-25% and P(HEMA-co-BA) with BA contents of 10-25% appeared to be non-cytotoxic and attractive for more specific cytocompatibility tests and in vivo studies with a view to their use as temporary skin substitutes.

薬剤によるコナダニ類駆除の研究 : 第 5 報 Fenthion 浸漬防虫畳シートのマウス, ラッテに対する影響, 特にコリンエステラーゼ活性について

The acaroid mite, Tyrophagus putrescentiae, is a household insect and commonly seen in Japan. This mite can be controlled using paper sheets which were sewed up to the entire upper and lower surfaces in Tatami-mat impregnated with fenthion. We conducted the safty evaluation on the paper sheets. Animals were maintained on the Tatami-mat or on the paper sheets during period of one, two and three months. The amounts of fenthion applied were 0 (untreated), 0.25,0.7,2.0 and 6.0g per m^2. In the practical amounts of 0.7g per m^2,the result indicated that there was no adverse effect on the general condition and appearance in the mice and rats as compared with untreated group. On the indirect contact test to the Tatami-mat, the inhibition of plasma and erythrocytes cholinesterase activities were observed in the mice after two to three months period. On the other hand, when animals were directly contacted on the paper sheets, the cholinesterase activity of plasma and body weight gain were reduced in the mice, and also, the inhibition of cholinesterase activity was observed in the brain of rats after one month period.