Material For Clinical Use Research Articles

Study on the poly(methyl methacrylate-acrylic acid)/calcium phosphate cement composite bound by chelation with enhanced water absorption and biomechanical properties

Polymethylmethacrylate (PMMA) bone cement has been widely used as a critical material for fixing prostheses and filling bone defects. The shrinkage of PMMA bone cement was addressed by the additives, however, the uneven integral water absorption and expansion performance as well as the deteriorated mechanical properties of the modified bone cement after immersion in phosphate buffered saline (PBS) and simulation body fluid (SBF) affected the long-term stability after implantation. Calcium phosphate cement (CPC) is a biomaterial with promising applications in orthopedics, whose hydration reaction provides an important driving force for the transfer of water. Besides, the mechanical properties of CPC can be enhanced with the curing process. In this study, CPC was utilized to modify the poly(methyl methacrylate-acrylic acid) [P(MMA-AA)] bone cement. The results demonstrated the successful construction of interconnected CPC water delivery networks in the P(MMA-AA)/CPC composite, the water absorption ratio and expansion ratio of the composite were up to 131.18 ± 9.14% and 168.19 ± 5.44%, respectively. Meanwhile, the transformation of CPC water delivery networks into rigid mechanical support networks as well as the chelation interaction between organic-inorganic enhanced the mechanical properties of the composite after immersion, the compressive strength after immersion reached 62.97 ± 0.97 MPa, which was 27.65% higher than that before immersion. The degradation ratio of the composite was up to 13.76 ± 0.23% after 9 days of immersion, which was 16.4% higher than that of CPC. Furthermore, composites exhibited superior biocompatibility as the release of Ca2+. Therefore, P(MMA-AA)/CPC composite serves as a promising medical filling material for clinical use.

Temporal characterization of hyaluronidases after peripheral nerve injury.

Hyaluronic acid (HA) is ubiquitously found in biological tissues and mediates wound healing mechanisms after injury by promoting cell migration and proliferation. With the development of tissue-engineered neural therapeutics, including off-the-shelf grafts for peripheral nerve repair, HA is an attractive material for clinical use because of its various biological roles. HA-based biomaterials have been carefully engineered to elicit specific in vivo host responses, however an important design feature that should be considered in these scaffolds is endogenous degradation. Hyaluronidases (HYALs) are the complementary enzymes that are responsible for HA turnover. Although HYAL expression has been widely characterized in various tissues, including the central nervous system, and for different pathologies, there remains a lack of knowledge of HYAL mediated turnover in peripheral nerve tissue. In this work, gene expression of two hyaluronidases, HYAL1 and HYAL2, and HA-binding receptor, CD44, were studied in two injury models: rat sciatic nerve crush and critical gap transection. HYAL2 and CD44 were shown to be upregulated 3 days after crush injury, whereas HYAL1 was upregulated at 3 weeks, which collectively demonstrate temporal patterning of HA breakdown. Additionally, differences were observed between HYAL and HA expression at 3 weeks when compared for both nerve injury models. The activity of HYAL in peripheral nerve tissue was determined to be approximately 0.11 μmol/min, which could be used to further model HA-based biomaterial breakdown for peripheral nerve applications. Overall, this work provides a landscape of HA turnover in peripheral nerve that can be used for future neural applications.

Adhesion and Surface Roughness of Apatite-Containing Carbomer and Improved Ionically Bioactive Resin Compared to Glass Ionomers.

The surface roughness of different glass-ionomer-based materials and their shear bond strength with a resin composite with and without thermal cycling were evaluated. Ketac Molar (KM, 3M ESPE, St. Paul, MN, USA), Glass Carbomer (GC, GCP Dental, Leiden, The Netherlands), Bioactive (BA, PULPDENT, Corporation, Watertown, MA, USA) and Fuji II LC (FJ, GC, Tokyo, Japan) were used to prepare the specimens and they were kept in distilled water at 37 °C for 24 h. The surface roughness of the specimens was measured with a profilometer (n = 6). A universal adhesive resin was applied on glass-ionomer materials and cylindrical universal composites were applied and polymerized, respectively (n = 16). The specimens were divided into two subgroups. The first subgroup was subjected to thermal cycling. Shear bond strength was investigated for both subgroups (n = 8). Stereomicroscopy and SEM examinations were performed. The roughest surface was obtained in the GC group (p < 0.05). The shear bond strength of the specimens without thermal cycling was higher than that of those with thermal cycling (p < 0.05). The lowest shear bond was measured in the GC group (p < 0.05). Although FJ, KM and BA have been observed to be suitable materials for clinical use, BA, in particular, is evidenced to become the best option among the materials we tested. GC cement's long-term performance needs to be improved.

Influence of surface treatment on repair bond strength of CAD/CAM long-term provisional restorative materials: an in vitro study

BackgroundThe surface treatment to improve the repair bond strength may vary because CAD/CAM provisional restoration polymers exhibit a variety of microstructures. This study was conducted to evaluate the effect of surface treatments on the repairability of three different CAD/CAM polymers for long-term provisional restorations.MethodsThirty specimens from each provisional restorative materials (CAD-Temp, Everest C-Temp, and PEEK) were divided into three groups: C: surfaces received no treatment; SB: surfaces were airborne particle abraded with 50 μm aluminum oxide; SB-T: surfaces received the same conditions as group SB in addition to thermocycling before and after treatment. Primer and nanohybrid repair resin composite were applied to the prepared CAD /CAM surfaces. The shear bond strength and the mode of failure were assessed. ANOVA and Tukey’s significant difference tests were used to evaluate the data.ResultsThe SB group had significantly higher repair SBS values (p < .001) compared to the other groups (C and SB-T). Everest C-Temp significantly recorded the highest repair SBS (17.84 ± 0.19 MPa) in group SB, while the lowest repair SBS values (5.51 ± 1.14 MPa) for CAD-Temp were recorded in group C. PEEK significantly recorded the second highest repair SBS (15.96 ± 0.18) in the SB group.ConclusionsEverest C-Temp had the highest repair SBS after an airborne abrasion particle. Thermocycling had no significant effect on the repair SBS for PEEK. Everest C-Temp and PEEK are recommended as long-term durable provisional materials for clinical use.

First-in-human evaluation of a biological regenerative vascular conduit for hemodialysis access.

The long-term survival and low complication rate of autogenous fistulas for hemodialysis access is often offset by early thrombosis and slow or failed maturation leading to the use of central venous catheters. A regenerative material may have the potential to overcome these limitations. A completely biological acellular vascular conduit was investigated in this first-in-human clinical study. With approval of the ethics board and patients' informed consent, five subjects were enrolled based on predetermined inclusion criteria. Five patients underwent implant of a novel acellular, biological tissue conduit (TRUE AVC™) in the upper arm in a curved configuration between brachial artery and axillary vein. After maturation, standard dialysis was commenced through the new access. Patients were followed up to 26 weeks with ultrasound and physical exam. Serum samples were evaluated for an immune response to the novel allogeneic human tissue implant. This new tissue conduit handled well surgically, with properties similar to that of native human vein. Post procedure conduit flow was excellent in all cases, averaging 1098 ± 388 ml/min at week 4 and remaining stable through 1248 ± 355 ml/min at 26 weeks. Surgical site healing was normal with no edema or erythema by week 4. Six-month primary assisted patency was 80% and secondary patency was 100%. Prescribed dialysis was successfully delivered without infection, and there was no significant change in conduit diameter. Serum testing showed no increase in PRA or IgG specific to the TRUE AVC. One implant required intervention at 5 months with thrombectomy and covered stent procedure. This first-in-human 6-month study with favorable patency and low complication rate establishes the initial safety and feasibility of this novel biological tissue conduit for dialysis access in patients with end-stage kidney disease. Its mechanical durability and lack of immune response establishes TRUE AVC as a potential regenerative material for clinical use.

Near infrared conjugated polymer nanoparticles (CPN™) for tracking cells using fluorescence and optoacoustic imaging.

Tracking the biodistribution of cell therapies is crucial for understanding their safety and efficacy. Optical imaging techniques are particularly useful for tracking cells due to their clinical translatability and potential for intra-operative use to validate cell delivery. However, there is a lack of appropriate optical probes for cell tracking. The only FDA-approved material for clinical use is indocyanine green (ICG). ICG can be used for both fluorescence and photoacoustic imaging, but is prone to photodegradation, and at higher concentrations, undergoes quenching and can adversely affect cell health. We have developed novel near-infrared imaging probes comprising conjugated polymer nanoparticles (CPNs™) that can be fine-tuned to absorb and emit light at specific wavelengths. To compare the performance of the CPNs™ with ICG for in vivo cell tracking, labelled mesenchymal stromal cells (MSCs) were injected subcutaneously in mice and detected using fluorescence imaging (FI) and a form of photoacoustic imaging called multispectral optoacoustic tomography (MSOT). MSCs labelled with either ICG or CPN™ 770 could be detected with FI, but only CPN™ 770-labelled MSCs could be detected with MSOT. These results show that CPNs™ show great promise for tracking cells in vivo using optical imaging techniques, and for some applications, out-perform ICG.

Development of structural material for the manufacture of facial prosthesis by 3D printing

Was to develop and evaluate the physical and mechanical properties of a structural material for the manufacture of facial epithesis using photopolymer printing technology. The study of the physical and mechanical properties of the developed structural material consisted of measuring the Shore hardness; determination of material strength at break, conditional yield strength, relative elongation at break and modulus of elasticity; the study of the characteristics described above, after artificial aging, simulating the daily use of a prosthesis. According to the test results, the samples of the studied material did not have a yield strength, they were torn at a deformation of 40-60%. The values of the conditional yield strength were 0.41±0.01 MPa, regardless of the time of the aging procedure. The values of the modulus of elasticity were 2.96±0.19 MPa and 2.88±0.14 MPa for the samples that underwent the aging procedure at 6 and 12 months, respectively. The results obtained were compared with the results of similar studies of structural materials used in 3D printing technology of facial prostheses, which allowed us to recommend the developed material for clinical use after evaluating its toxicological and biological characteristics.

Update on Dental Luting Materials.

A dental luting material aids in the retention and stability of indirect restorations on the prepared tooth structure. In dentistry, clinicians are using a wide range of luting materials for the cementation of indirect restorations. Zinc oxide eugenol and non-eugenol cements, zinc phosphate cement, zinc polycarboxylate cement, glass ionomer cement and resin cements are common dental cements used in dentistry. Each luting material or cement possesses unique properties and clinical implications. An ideal luting cement should be biocompatible, insoluble, resistant to thermal and chemical assaults, antibacterial, aesthetic, simple and easy to use. It should have high strength properties under tension, shear and compression to resist stress at the restoration-tooth interface, as well as adequate working and setting times. So far, no luting material possesses all of these properties of an ideal cement. Scientists have been modifying the conventional luting cements to improve the material's clinical performance and developing novel materials for clinical use. To achieve the best clinical outcome, clinicians should update their knowledge and gain a good understanding of the luting materials so that they can make a wise clinical decision on the material selection and obtain an insight into the development of luting cements. Therefore, the objective of this study is to provide a discussion on the physical, chemical, adhesive and aesthetic properties of common luting materials. The clinical indications of these luting materials are suggested based on their properties. In addition, overviews of the modification of the conventional luting materials and the newly developed luting materials are provided.

On the Mechanical Properties of Hybrid Dental Materials for CAD/CAM Restorations.

Two hybrid dental materials available for computer-aided design and manufacturing (CAD/CAM) dental restorations have been selected to explore their potential. On the one hand, the scarcely investigated polymer-based material Vita Enamic® (VE) and, on the other hand, the leucite-based material IPS Empress® CAD (EC). Their micro-structure and mechanical performance were analyzed in two environments: directly as received by the manufacturer (AR), and after immersion and storage in artificial saliva (AS) for 30 days to determine the influence of the saliva effect. To avoid an inappropriate selection of materials for clinical use, a full understanding of their mechanical behavior is essential. Therefore, this investigation aims to determine the micro-structural and chemical composition by field emission scanning electron microscopy (FE-SEM) and X-ray fluorescence analysis, establishing the density, micro- and nano-hardness, the nano-elastic modulus, and the flexural strength and fracture toughness (by introducing a femto-laser notch to replicate a real crack). In addition, fracture surfaces of the broken samples were analyzed to correlate the failure micro-mechanisms with their mechanical properties. Results indicate that while the crystalline phase of the materials is very similar (composed of SiO2 and Al2O3), the micro-structure and mechanical behavior is not. The material EC, with finer micro-structure, exhibits a higher mechanical performance but with greater variability of results. Furthermore, the material VE, with a 25 vol.% polymer phase, shows a mechanical performance similar to enamel and dentin and therefore more similar to human behavior.

Pre-Menstrual Dysphoric Disorder (PMDD) in Young People: What We Know About It, the Role of CBT as a Treatment Option, and the Development of High-Quality Psychoeducation Material for Clinical Use

AimsWe aim to explain more about PMDD in young people and explore the evidence looking at the role of CBT as an intervention. We aim to develop high-quality psychoeducation material with the involvement of young people, to be able to offer clinically relevant information and empower young people with PMDD.MethodsA literature search was conducted in 2019 and updated in February 2022 using the Cochrane Library, Psych-info, MEDLINE, Cinahl, EMBASE and Google Scholar, to look at the evidence available for CBT in young people with PMDD or PMS. The search included PMS as well as PMDD due to the heterogeneity in definitions used in studies.Focus groups with young people are underway to develop high quality written psychoeducation material about PMDD.ResultsThere were no specific studies looking at CBT as an intervention in young women under the age of 18 with PMS or PMDD. There was one intervention study with a treatment arm of psychoeducation in 62 young people under 18 with PMS versus a no treatment group (Taghizadeh 2013), with improvement in symptoms after 3 months from baseline reported.There were more studies available in women over the age of 18. The search identified 3 meta- analyses in 2009 and 2012 (Busse 2009, Lusty, 2009; Kleinstauber 2012) and a more recent systematic review (Landolt 2020). Kleinsteiber et al included 22 RCTs, with a median age of 39, and broadly showed CBT to have a small to medium positive effect size, although any conclusions were limited due to the small numbers involved in the individual trials and methodological flaws. Landolt 2020 looked at CBT or elements of CBT as an intervention arm over the last 30 years or so in woman of all ages. Variations of CBT including virtual, group, couple and psychoeducation alone were included, and all were reported to have favourable outcomes.ConclusionThere is a huge gap in research looking at PMDD in the adolescent population. Translating research from adults is not ideal. Increasing awareness and developing psychoeducation is a step in the right direction.

In vitro and in vivo studies on bacteria and encrustation resistance of heparin/poly-L-lysine-Cu nanoparticles coating mediated by PDA for ureteral stent application.

Ureteral stents are commonly utilized as a medical device to aid the flow of urine. However, biofilm formation and encrustation complications have been clinical problems. To overcome this challenge, heparin/poly-L-lysine-copper (Hep/PLL-Cu) nanoparticle was immobilized on a dopamine-coated polyurethane surface (PU/NPs). The stability and structural properties of the nanoparticles were characterized by Zeta potential, poly dispersion index, transmission electron microscopy, atom force microscopy and contact angle. The surface composition, antibacterial potency, encrustation resistance rate and biocompatibility of PU/NPs were investigated by scanning electron microscope, X-ray photoelectron spectroscopy, antibacterial assay and MTS assay, respectively. In addition, the anti-encrustation property was studied by implanting coated NPs stents in the rat bladder for 7 days. It was shown that the size and distribution of Hep/PLL-Cu nanoparticles were uniform. PU/NPs could inhibit Proteus mirabilis proliferation and biofilm formation, and exhibit no cytotoxicity. Less encrustation (Ca and Mg salt) was deposited both in vitro and in vivo on samples, demonstrating that the NPs coating could be a potential surface modification method of ureteral material for clinical use.

Biocompatibility of NbTaTiVZr with Surface Modifications for Osteoblasts.

We report a potential biomedical material, NbTaTiVZr, and the impact of surface roughness on the osteoblast culture and later behavior based on in vitro tests of preosteoblasts. Cell activities such as adhesion, viability, and typical protein activity on NbTaTiVZr showed comparable results with that of commercially pure Ti (CP-Ti). In addition, NbTaTiVZr with a smooth surface exhibits better cell adhesion, viability, and typical protein activity which shows that surface modification can improve the biocompatibility of NbTaTiVZr. This supports the biological evidence and shows that NbTaTiVZr can potentially be evaluated as a biomedical material for clinical use.

63 - Aesthetic Properties of New Hybrid Resin Block for CAD/CAM

Hybrid resin block for CAD/CAM are known as useful material for clinical use. In last year, hybrid resin crown for CAD/CAM restoration in anterior teeth was approved by Japanese national health insurance. Recently we launched highly aesthetic resin block CERASMART LAYER only in Japan. CERASMART LAYER can materialize an aesthetic appearance close to natural teeth because it has three-layered composition. The purpose of this study was to evaluate aesthetic properties of the new material and other products in the marketplace. Five materials were selected for experimental and analysis, 1) CERASMART LAYER (GC Corp.), 2) KATANA AVENCIA N (Kuraray), 3) KZR-CAD HR Block4 E-VA (YAMAKIN), 4) HC HARD AN (SHOFU), 5) ENAMIC Multicolor (VITA). These blocks were evaluated by Tooth-brush test. The specimen of tooth-brush test was formed into anterior teeth shape by using Cerec inLab MC XL (Dentsply Sirona) and was recontoured and polished in accordance with instructions. The specimen was placed in silicone mold in order to define the position of abrasion by brush. The test was conducted with tooth-brush machine for 12,000 cycles. The surface morphology of specimens before and after test was investigated with laser microscope (KEYENCE) and evaluated surface roughness (Ra value). All results were analyzed by one-way ANOVA (p<0.05). The results of tooth-brush test, CERASMART LAYER showed the lowest Ra value after 12,000 cycles of tooth-brush abrasion because of uniformly dispersion and high loading of inorganic nano-filler. In addition, only CERASMART LAYER and KATANA AVENCIA N showed glossy surface in spite of after 12,000 cycles of tooth-brush test. From the results, CERASMART LAYER exhibited the lowest surface roughness and highly gloss retention. Therefore, it is expected that CERASMART LAYER is a durable and aesthetic material and may have clinical advantages.

One-pot synthesis and enzyme-responsiveness of amphiphilic doxorubicin prodrug nanomicelles for cancer therapeutics.

In this study, we report a one-pot synthesis and enzyme-responsiveness of polyethylene glycol (PEG) and glutamic acid (Glu)-based amphiphilic doxorubicin (DOX) prodrug nanomicelles for cancer therapeutics. The nanomicelles were accomplished by esterification and amidation reactions. The nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) data confirmed the structure of nanomicelles. The DOX-loaded nanomicelles showed a DLS-measured average size of 107 nm and excellent stability in phosphate-buffered saline (PBS) for 7 days. The drug loading and cumulative release rates were measured by ultraviolet-visible (UV-vis) spectrophotometry at 481 nm. The cumulative release rate could reach 100% in an enzyme-rich environment. Further, the therapeutic efficiency of nanomicelles to cancer cells was determined by cell viability and cellular uptake and distribution using HeLa cells. The cell viability study showed that the DOX-loaded nanomicelles could effectively inhibit the HeLa cell proliferation. The cellular uptake study confirmed that the nanomicelles could be effectively ingested by HeLa cells and distributed into cell nuclei. Based on the collective experimental data, this study demonstrated that the synthesized nanomicellar prodrug of DOX is a potential candidate for cancer therapeutics.

The effect of steam sterilization on different 3D printable materials for surgical use in veterinary medicine

BackgroundDifferent 3D-printed materials polyactic acid (PLA), polyamide (PA), polycarbonates (PC), acrylonitrile butadiene styrene (ABS) and GreenTEC Pro®I have been considered for surgical templates, but there is a sparity of data about how these materials are affected by steam sterilization. The aim of the current study was to test if and how these materials change morphologically when high temperature, pressure and humidity are applied during the steam sterilization process. The overall aim is to create patient-specific sawing templates for performing corrective osteotomies. After the designing process, test-specimens with five different materials: PLA, PC, ABS, PA and GreenTEC Pro® were 3D-printed in two filling grades (30 and 100%). The FDM method was used for printing. After 3D-printing, the test-specimens were steam sterilized with a standard program lasting 20 min, at a temperature of 121 °C and a pressure of 2–3 bar. In order to measure the deviation of the printed model, we measured the individual test-specimens before and after steam sterilization using a sliding gauge.ResultsPC, PA and ABS showed great morphological deviations from the template after 3D-printing and steam sterilization (> 1%) respectively. ABS proved unsuitable for steam sterilization. PLA and GreenTEC Pro® demonstrated fewer morphological deviations both before and after sterilization. Therefore, we decided to perform a second test just with PLA and Green-TEC Pro® to find out which material has the highest stability and is probably able to be used for clinical application. The smallest deviations were found with the GreenTEC Pro® solid body. After autoclaving, the specimens showed a deviation from the planned body and remained below the 1% limit.ConclusionSteam sterilization causes morphological deviations in 3D printed objects. GreenTEC Pro® seems to be a suitable material for clinical use, not only for intraoperative use, but also for precise modeling. Microbiological examination, as well as biomechanical tests, should be performed to further assess whether intraoperative use is possible.

Conceptualization of Bioactive Materials in Dental Caries Prevention

Clinicians always face a challenge in selecting the appropriate material for clinical use. Presently, the term bioactive is being used judiciously and unquestionably in the field of dental materials. The introduction of nanotechnology brought about a revolution in material science leading to the development of bioactive materials for caries prevention and management. This review comprehensively evaluates the use of bioactive materials for modification of the oral biome, prevention of dental caries, and the management of dental caries as restorative materials. Six online database (PubMed, Scopus, Science Direct, Embase, Web of Science, and Cochrane library) were systematically searched using broad keywords. Published articles were scrutinized, analyzed and the full-text articles were selected. Data reveals relatively limited application of tissue engineering and regeneration for enamel and dentin due to their limited ability to remodel. However, many steps are being taken in biomimetic approach for the modification of dentin. The path to overcoming any challenges will require active collaboration among clinicians, a material scientist and pulp biologist.

Bilayered scaffold with 3D printed stiff subchondral bony compartment to provide constant mechanical support for long-term cartilage regeneration.

Background/ObjectiveWe seek to figure out the effect of stable and powerful mechanical microenvironment provided by Ti alloy as a part of subchondral bone scaffold on long-term cartilage regeneration.Methods: we developed a bilayered osteochondral scaffold based on the assumption that a stiff subchondral bony compartment would provide stable mechanical support for cartilage regeneration and enhance subchondral bone regeneration. The subchondral bony compartment was prepared from 3D printed Ti alloy, and the cartilage compartment was created from a freeze-dried collagen sponge, which was reinforced by poly-lactic-co-glycolic acid (PLGA).ResultsIn vitro evaluations confirmed the biocompatibility of the scaffold materials, while in vivo evaluations demonstrated that the mechanical support provided by 3D printed Ti alloy layer plays an important role in the long-term regeneration of cartilage by accelerating osteochondral formation and its integration with the adjacent host tissue in osteochondral defect model at rabbit femoral trochlea after 24 weeks.ConclusionMechanical support provided by 3D printing Ti alloy promotes cartilage regeneration by promoting subchondral bone regeneration and providing mechanical support platform for cartilage synergistically.Translational potential statementThe raw materials used in our double-layer osteochondral scaffolds are all FDA approved materials for clinical use. 3D printed titanium alloy scaffolds can promote bone regeneration and provide mechanical support for cartilage regeneration, which is very suitable for clinical scenes of osteochondral defects. In fact, we are conducting clinical trials based on our scaffolds. We believe that in the near future, the scaffold we designed and developed can be formally applied in clinical practice.

Hybrid material mimics a hypoxic environment to promote regeneration of peripheral nerves

Between nerve defects, a bridge formed by multiple cells is the fundamental structure for guiding axons across this damaged region. Here, we developed a functional material that mimics hypoxia during the early stages of nerve regeneration by deferoxamine. We used this material and single-cell sequencing to analyze the “bridge” structure between peripheral nerve defects. We found that hypoxia in damaged tissues might play a key role in stimulating macrophages, promoting endothelial-to-mesenchymal transition, and driving the migration of endothelial cells to the injured region to form regenerative bridge tissue and guide the subsequent regeneration of Schwann cells and axons. The results showed that the final nerve defect repair outcomes were similar with autografts after intervention by this material. This study challenges the view that hypoxia is exclusively involved in peripheral nerve regeneration and provides a potentially valuable candidate material for clinical use.

Tissue engineering: recent advances and review of clinical outcome for urethral strictures.

Urethrotomy remains the first-line therapy in the treatment of a urethral stricture despite data showing no real chance of a cure after repeated urethrotomies. An anastomotic or an augmentation urethroplasty using oral mucosa can be offered to patients following failed urethrotomy. The potential for a tissue engineered solution as an alternative to native tissue has been explored in recent years and is reviewed in this article. More than 80 preclinical studies have investigated a tissue-engineered approach for urethral reconstruction mostly using decellularized natural scaffolds derived from natural extracellular matrix with or without cell seeding. The animal models used in preclinical testing are not representative of disease processes seen with strictures in man. The available clinical studies are based on small noncontrolled series. There is a potential role for tissue engineering to provide a material for substitution urethroplasty and work has demonstrated this. Further work will require a rigorous basic science programme and adequate evaluation of the material prior to its introduction into clinical practice. The research with tissue engineering applied to the urethra has not yet been resulted in a widely available material for clinical use that approaches the efficacy seen with the use of autologous grafts.

Long term efficacy and fate of a right ventricular outflow tract replacement using an elastomeric cardiac patch consisting of caprolactone and D,L-lactide copolymers

For decades, researchers have investigated the ideal material for clinical use in the cardiovascular field. Several substitute materials are used clinically, but each has drawbacks. Recently we developed biodegradable and elastic poly(ε-caprolactone-co-D,L-lactide) (P(CL-DLLA)) copolymers by adjusting the CL/DLLA composition, and evaluated the long-term efficacy and outcomes of these copolymers when used for right ventricular outflow tract (RVOT) replacement. This P(CL-DLLA) material was processed into a circular patch and used to replace a surgical defect in the RVOT of adult rats. Control rats were implanted with expanded polytetrafluoroethylene (ePTFE). Histologic evaluation was performed at 8, 24, and 48 weeks post-surgery. All animals survived the surgery with no aneurysm formation or thrombus. In all periods, ePTFE demonstrated fibrous tissue. In contrast, at 8 weeks P(CL-DLLA) showed infiltration of macrophages and fibroblast-like cells into the remaining material. At 24 weeks, P(CL-DLLA) was absorbed completely, and muscle-like tissue was present with positive staining for α-sarcomeric actinin and cardiac troponin T (cTnT). At 48 weeks, the cTnT-positive area had increased. The biodegradable and elastic P(CL-DLLA) induced cardiac regeneration throughout the 48-week study period. Future application of this material as a cardiovascular scaffold seems promising. Statement of significanceBiomaterials for reconstruction of tissue deficiencies in cardiovascular surgery require having suitable mechanical properties for cardiac tissue and biodegradation resulting in native tissue growth. Several biodegradable polymers such as poly-ε-caprolactone (PCL) and polylactic acid (PLA) have excellent biocompatibility and already been widely used clinically. In general, PCL and PLA are quite mechanically rigid. Meanwhile, significant elasticity is required in the high-pressure environment of the heart while the material is being replaced by new tissue. The present study provides a novel four-armed crosslinked poly(ε-caprolactone-co-D,L-lactide) (i.e., P(CL-DLLA)) material for cardiac patch, which was demonstrated properties including tissue-compatible, super-elastic nature, that made it suitable for long-term, in vivo RVOT repair. This super-elastic biomaterial could be useful for reconstruction of various muscular tissues deficiencies.