Characteristics of pediatric patients claimed with acute upper respiratory infection during otorhinolaryngology consultations: A descriptive study of a large Japanese medical claims database.

This study aimed to clarify other diseases claimed simultaneously with acute upper respiratory infection (URI), antibiotic prescriptions, and examinations associated with infectious diseases in pediatric patients with acute URI insurance claims at otorhinolaryngology outpatient visits. Pediatric patients who visited an otolaryngology department between 2019 and 2021 and were definitively diagnosed with URI were selected using a large Japanese medical claims database. Patient backgrounds, antibiotic use, and examinations were descriptively evaluated. In total, 8010 patients were included in the analysis. The median number (interquartile range) of diseases claimed in the same month as acute URI was 4 (3-6). Only 519 (6.5 %) patients were claimed as acute URI alone. Regardless of the prescription of antibiotics, the most commonly redundantly claimed disease in these patients was allergic rhinitis, followed by acute bronchitis, acute sinusitis, and earwax impaction. The frequently prescribed antibiotics were third-generation cephalosporins, macrolides, and penicillins with extended-spectrum, including amoxicillin which was recommended by the Japanese manual; the proportion of patients with examinations was low (2.9-21.7 %). Among patients with acute URI, diagnoses requiring antibiotics were also claimed; therefore, when evaluating acute URI using the Japanese medical claims database, care must be taken in patient selection. Moreover, the implementation rate of examinations necessary for diagnosis was low, so there is an urgent need to develop an environment where examinations can be conducted in outpatient settings.

Risk of a second cancer and infection in patients with indolent B-cell lymphoma exposed to first-line bendamustine plus rituximab: A retrospective analysis of an administrative claims database.

Bendamustine has a potent immunosuppressive effect because it causes T-cell lymphopenia, which might lead to a second primary malignancy (SPM) and would increase the risk of infection. Using the Medical Data Vision administrative claims database, we compared the cumulative incidence of SPM, infections within 6 months, and overall survival (OS) among untreated patients with indolent B-cell lymphomas (iBCL) who received rituximab-based chemotherapy between 2009 and 2020. Patients with grade 3b follicular lymphoma or a previous history of malignancy were excluded. Eligible 5234 patients were assigned to three cohorts: rituximab monotherapy (N = 780), RCHOP/RCVP/RTHPCOP (doxorubicin replaced with pirarubicin) (N = 2298), or bendamustine/rituximab (BR) (N = 2156). There were 589 recorded SPMs, of which myelodysplastic syndromes were the most common (1.7%). The cumulative incidence of SPM was significantly higher in patients treated with BR than in those treated with rituximab monotherapy (p < 0.01) or RCHOP/RCVP/RTHPCOP (p < 0.0001): the 5-year cumulative incidence function was 18.1%, 12.5%, and 12.9%, respectively. In the Fine-Gray subdistribution hazards model, BR showed a significantly higher cumulative incidence of SPM than RCHOP/RCVP/RTHPCOP (subhazard ratio, 1.33; 95% confidence interval [CI], 1.10-1.61). Furthermore, in sensitivity analysis, a nested case-control study using an entire cohort showed consistent results: the SPM odds ratios (95% CI) of first-line bendamustine, bendamustine after first-line, and any-line bendamustine were 1.43 (1.14-1.78), 1.26 (0.96-1.64), and 1.33 (1.09-1.62), respectively. Regarding infections, adjusted odds ratios (95% CI) of BR compared to RCHOP/RCVP/RTHPCOP were as follows: cytomegalovirus infection, 13.7 (4.88-38.4); bacterial pneumonia, 0.63 (0.50-0.78); and pneumocystis pneumonia, 0.24 (0.11-0.53). There was no significant difference in OS between RCHOP/RCVP/RTHPCOP and BR in patients with follicular, mantle cell, marginal zone, or lymphoplasmacytic lymphomas. In conclusion, treatment strategies that consider the risk of SPM and infections after chemotherapy are warranted in patients with iBCL.

Trends in Implementation of Loading Dose of Voriconazole from 2010 to 2019 and Influencing Factors of Loading Dose Based on a Japanese Administrative Claim Database: A Retrospective Cohort Study.

A loading dose of voriconazole (VRCZ) is recommended to increase its blood concentration at an early stage. However, the trends in the implementation of the loading dose in VRCZ in Japan has not yet been clarified. In addition, although pharmacists play many important roles in antimicrobial stewardship, the effect of pharmacist intervention on the implementation of a loading dose of VRCZ has not yet been reported. Therefore, this study aimed to clarify the implementation of loading dose of VRCZ and the influencing factors of loading dose. This study used an administrative claims database that included patients who received injectable VRCZ between 2010 and 2019. The implementation of loading doses in the VRCZ was evaluated annually. Multivariate logistic regression analysis was performed to identify the factors influencing loading dose. Overall, 2197 patients were included. The implementation rate of the loading dose remained below 65% throughout the study period. Among medical fees that can be calculated through pharmacist intervention, only the infection prevention and control premium significantly increased the implementation of loading dose of VRCZ (odds ratio: 1.587, 95% confidence interval: 1.053-2.392). In conclusion, antifungal stewardship may have been promoted at medical institutions that established infection prevention and control. In the future, pharmacists will need to intervene more actively from the beginning of VRCZ administration.

A study of trends and factors associated with therapeutic drug monitoring (TDM) implementation for arbekacin treatment using a large Japanese medical claims database.

INTRODUCTION: Reimbursements for pharmacist interventions and infectious disease teams have recently been introduced in Japan. Arbekacin (ABK) is used to treat pneumonia and sepsis caused by methicillin-resistant Staphylococcus aureus, and therapeutic drug monitoring (TDM) is recommended. This study aimed to clarify the trend in TDM implementation for ABK over time and the factors associated with TDM implementation using a claims database. METHODS: Data of patients aged ≥15 years who received ABK for ≥3 consecutive days between 2010 and 2019 were extracted from a large Japanese medical claims database. The proportion of reimbursements claimed for TDM, pharmacist interventions, and the setup of infectious disease teams for each year were calculated. The factors associated with TDM implementation were identified using multivariate logistic regression analysis. RESULTS: The proportion of TDM implementation for ABK increased by 9.1% from 2010 to 2019, but it remained less than 40% throughout this period. The proportion of TDM implementation was higher in patients who claimed reimbursements for pharmacist interventions than in patients who did not. Logistic regression analysis showed that the stationing of pharmacists in wards and long-term ABK treatment were significantly associated with TDM implementation. CONCLUSIONS: From 2010 to 2019, the proportion of TDM implementation for ABK was significantly low. Moreover, the factors associated with TDM implementation were clarified. An environment wherein pharmacists can help implement TDM for patients receiving ABK would be beneficial.

Trends in Antipseudomonal Agent Use Based on the 2006 to 2015 Sales Data in Japan.

Pseudomonas aeruginosa resistance is a major issue worldwide. Drug resistance is related to inappropriate antibiotic use. Because antipseudomonal agents have a wide spectrum, they must be used appropriately. The purpose of this study was to clarify the trends in antipseudomonal agent use in Japan based on sales data from 2006 to 2015. The total antipseudomonal agent use was increased significantly (r = 0.10, Pfor trend = 0.00040). The proportion of fluoroquinolones use was the highest throughout the year, accounting for 88.6-91.4%. The use of piperacillin/tazobactam significantly increased. The increased use of these drugs may be due to the launch of higher doses and additional indications. On the other hand, for antipseudomonal agents, parenteral carbapenems use was 2.7-3.7%, but it has remained unchanged over the years. In Japan, permit and notification systems have been introduced to prevent the inappropriate use of parenteral carbapenems in medical institutions. It was speculated that these efforts suppressed the inappropriate use of parenteral carbapenems. This study clarified the trend of antipseudomonal agent use in Japan from 2006 to 2015. It is important to continue monitoring antipseudomonal agents use to conduct appropriate antimicrobial resistance measures.

An alternative index for evaluating AMU and anti-methicillin-resistant Staphylococcus aureus agent use: A study based on the National Database of Health Insurance Claims and Specific Health Checkups data of Japan.

INTRODUCTION: Anti-methicillin-resistant Staphylococcus aureus (MRSA) agents have different doses and administration periods. Thus, it is difficult to evaluate antimicrobial use (AMU) of anti-MRSA agents using defined daily doses per 1000 inhabitants per day (DID) or days of therapy per 1000 inhabitants per day (DOTID). This study aimed to evaluate the relationship between anti-MRSA agent use and resistant bacteria using the number of patients per 1000 inhabitants per day (PID) as an alternative index of AMU. METHODS: AMU data for anti-MRSA agents were collected from the National Database of Health Insurance Claims and Specific Health Checkups (NDB) in 2016. The relationship between PID and DID or DOTID was evaluated. The number of patients with MRSA isolated was obtained from Japan Nosocomial Infections Surveillance, and their correlation with PID was analyzed. The rate of anti-MRSA agent use in each prefecture was investigated. RESULTS: PID showed a significant linear relationship with both DID and DOTID (all p < 0.0001). PID was significantly correlated with the number of patients with MRSA isolated. Additionally, the rate of anti-MRSA agent use was markedly different in each region. CONCLUSIONS: PID is not affected by doses and administration periods, and thus may be an alternative index for the selective pressure of antibiotics. Evaluating AMU using PID based on NDB data will help in the development of effective antimicrobial resistance measures.

Trends of Antifungal Use Based on Sales Data in Japan from 2006 to 2015.

The detailed epidemiology of invasive mycoses and superficial mycoses has not been clarified in Japan. In addition, treatment options have increased because of novel antifungals and/or guidelines for fungal infection. In the present study, we aimed to clarify the trends of antifungal use in Japan from 2006 to 2015 based on sales data to serve as an alternative indicator of fungal infection trends. We found that the total antifungal use decreased over time (r = -0.057, Pfor trend < 0.0001). Oral and parenteral use significantly decreased by 44.1% (r = -0.056, Pfor trend < 0.0001) and 27.1% (r = -0.0012, Pfor trend = 0.00061), respectively. The trend of antifungal use for superficial mycoses significantly decreased by 49.8% (r = -0.061, Pfor trend < 0.0001). However, the trend of antifungal use for invasive mycoses was significantly increased by 19.9% (r = 0.0032, Pfor trend = 0.00045). In Japan, the increase in the number of immunocompromised patients might be associated with the increase in the frequency of antifungal use for invasive mycoses. This is the first study to clarify the trends of antifungal use in Japan. Further research is needed to establish a continuous surveillance system to compare fungal infections between Japan and the world.

Trends of the Use of Anti-methicillin-Resistant Staphylococcus aureus Agents in Japan Based on Sales Data from 2006 to 2015.

Patterns of the use of anti-methicillin-resistant Staphylococcus aureus (MRSA) agents in Japan might be influenced by the launch of new anti-MRSA agents, the publication of relevant guidelines, and the increase in the number of generic medicines. However, as anti-MRSA agents are included in multiple anatomical therapeutic chemical classifications, such as glycopeptides and aminoglycosides, the trends of the use of individual anti-MRSA agents remain unclear. Here, we aimed to clarify the trends of anti-MRSA agent use in Japan from 2006 to 2015 based on sales data. Total anti-MRSA agent use was found to have significantly increased from 2006 to 2015 (Pfor trend = 0.027, r = 0.00022). Individual trends for vancomycin (VCM), daptomycin, and linezolid (LZD) use showed significant increases, while those for arbekacin (ABK) and teicoplanin (TEIC) showed decreases. In addition, oral LZD use significantly increased, while there was no significant change in intravenous LZD use. The ratio of oral LZD use to total LZD use increased from 25.5% in 2006 to 39.9% in 2015. Meanwhile, TEIC and ABK use decreased, while VCM use increased, following the launch of generic medicines. These results might reflect the status of guideline compliance, the launch of new anti-MRSA agents, and the decline in the sales promotion of the original medicines. It is extremely important to investigate trends for the use of not only different antibiotic groups but also individual antibiotics to develop and implement antimicrobial resistance countermeasures.

The Trend for Antibiotic Use for Clostridioides (Clostridium) difficile Infection in Japan.

In Japan, there is no national surveillance study of Clostridioides (Clostridium) difficile infection (CDI), and details about the epidemiology and treatment status of CDI are unknown. Additionally, clinical practice guidelines (CPGs) for CDI are published by four different institutions. All CPGs recommend that the antimicrobials, vancomycin (VCM) and metronidazole (MNZ), should be selected according to disease severity. However, the trends for VCM and MNZ use in Japan remain unclear. Therefore, this study was aimed at clarifying the secular trends for VCM and MNZ use based on sales data from 2006 to 2015 and discussing its impact on CDI status and drug costs. This is the first study to clarify the antibiotic use trends for CDI treatment. We found that the total use increased over time (r = 0.0013, Pfor trend < 0.0001). While VCM use significantly decreased (r = -0.0003, Pfor trend = 0.0002), MNZ use increased (r = 0.0017, Pfor trend < 0.0001). These results show that although treatment for CDI was in line with CPGs, CDI incidence might be on an increasing trend. Additionally, despite the increased total use, the total drug costs decreased by 55% ($ 25 million) from 2006 to 2015. It was also surmised that CDI treatment in compliance with CPGs would lead to a reduction in drug costs. Hence, to understand the epidemiology of CDI, it is important to continuously investigate the use of drugs used for CDI therapy.

Chemoselective Nucleophilic Functionalizations of Aromatic Aldehydes and Acetals via Pyridinium Salt Intermediates.

The development of a novel chemoselective functionalization can diversify the strategy for synthesizing the target molecules. The perfect chemoselectivity between aromatic and aliphatic aldehydes is difficult to achieve by the previous methods. The aromatic aldehyde-selective nucleophilic addition in the presence of aliphatic aldehydes was newly accomplished. Namely, the aromatic aldehyde-selective nucleophilic addition using arenes and allyl silanes proceeded in the presence of trialkylsilyl triflate and 2,2'-bipyridyl, while the aliphatic aldehydes completely remained unchanged. The reactive pyridinium-type salt intermediate derived from an aromatic aldehyde chemoselectively underwent the nucleophilic substitution. Moreover, the aromatic acetals as the protected aldehydes could be directly transformed into similar pyridinium salt intermediates, which reacted with various nucleophiles coexisting with the aliphatic aldehydes.

Gold-Catalyzed Benzylic Azidation of Phthalans and Isochromans and Subsequent FeCl3-Catalyzed Nucleophilic Substitutions.

The benzylic positions of the phthalan and isochroman derivatives (1) as benzene-fused cyclic ethers effectively underwent gold-catalyzed direct azidation using trimethylsilylazide (TMSN3) to give the corresponding 1-azidated products (2) possessing the N,O-acetal partial structure. The azido group of the N,O-acetal behaved as a leaving group in the presence of catalytic iron(III) chloride, and 1-aryl or allyl phthalan and isochroman derivatives were obtained by nucleophilic arylation or allylation, respectively. Meanwhile, a double nucleophilic substitution toward the 1-azidated products (2) occurred at the 1-position using indole derivatives as a nucleophile accompanied by elimination of the azido group and subsequent ring opening of the cyclic ether nucleus produced the bisindolylarylmethane derivatives.

Chemoselective and direct functionalization of methyl benzyl ethers and unsymmetrical dibenzyl ethers by using iron trichloride.

Methyl and benzyl ethers are widely utilized as protected alcohols due to their chemical stability, such as the low reactivity of the methoxy and benzyloxy groups as leaving groups under nucleophilic conditions. We have established the direct azidation of chemically stable methyl and benzyl ethers derived from secondary and tertiary benzyl alcohols. The present azidation chemoselectively proceeds at the secondary or tertiary benzylic positions of methyl benzyl ethers or unsymmetrical dibenzyl ethers and is also applicable to direct allylation, alkynylation, and cyanation reactions, as well as the azidation. The present methodologies provide not only a novel chemoselectivity but also the advantage of shortened synthetic steps, due to the direct process without the deprotection of the methyl and benzyl ethers.

Iron-catalyzed Friedel-Crafts benzylation with benzyl TMS ethers at room temperature.

Friedel-Crafts benzylations between unactivated arenes and benzyl alcohol derivatives are clean and straightforward processes to construct biologically useful di- and tri-arylmethanes. We have established an efficient iron-catalyzed Friedel-Crafts benzylation method at room temperature that uses benzyl TMS ethers as substrates, which are poorly reactive under common nucleophilic substitution conditions. The reaction seems to progress through iron-catalyzed self-condensation of the benzyl TMS ether to the corresponding dibenzylic ether. The use of excess arene relative to benzyl TMS ether produced mono-benzylated arene (di- and tri-arylmethane products), whereas the use of excess benzyl TMS ether versus arene provided bis-benzylated arene (polyarylated products) in high yields and regioselectivities. In previous methods, the latter double Friedel-Crafts benzylations hardly proceed.

Effectiveness of Noncertified Pharmacist-Led Antimicrobial Stewardship Programs in a Medium-Sized Hospital Without an Infectious Disease Specialist: A Retrospective Pre-Post Study.

Background: Few studies have reported the outcomes of antimicrobial stewardship programs (ASPs) implemented without infectious disease (ID) physician or pharmacist specialists. We implemented interventions that included providing antimicrobial optimization recommendations through a pharmacist-led team using prospective audit and feedback. This study evaluated different types of interventions and their impact on the outcomes of ASPs in a medium-sized hospital without ID specialists. Methods: This retrospective pre-post study included adult inpatients treated with intravenous antimicrobials between April 2016 and March 2020. Outcome (eg, length of hospital stay [LOS], drug cost) and process measures (eg, type of intervention, length of therapy) were compared between 2 time periods: pre-ASP (April 2016-March 2018) and post-ASP (April 2018-March 2020). Results: We included 5419 and 5634 patients in the pre- and post-ASP periods, respectively. The most common types of interventions were adjusting length of therapy (49.5%), additional laboratory tests (27.1%), antimicrobial change (16.2%), and dosage of antimicrobial (7.1%). After ASP implementation, LOS significantly decreased (14.8 vs 13.8 days, P < .01), along with the length of therapy, empirical use of antipseudomonal and anti-methicillin-resistant Staphylococcus aureus drugs, and number of days to de-escalation. No significant differences were noted in 30-day mortality, 30-day readmission, or de-escalation rates. On average, the antimicrobial cost per hospitalization decreased from US$173.03 to US$120.66. Conclusions: Pharmacist-led ASP interventions that focus on the length of therapy have the potential to reduce LOS in hospitals without ID specialists. Overall, this study showed that ASPs can be effectively implemented in medium-sized hospitals without ID specialists.

Fabrication of cell-laden microbeads and microcapsules composed of bacterial polyglucuronic acid.

In the past decades, the microencapsulation of mammalian cells into microparticles has been extensively studied for various in vitro and in vivo applications. The aim of this study was to demonstrate the viability of bacterial polyglucuronic acid (PGU), an exopolysaccharide derived from bacteria and composed of glucuronic acid units, as an effective material for cell microencapsulation. Using the method of dropping an aqueous solution of PGU-containing cells into a Ca2+-loaded solution, we produced spherical PGU microbeads with >93 % viability of the encapsulated human hepatoma HepG2 cells. Hollow-core microcapsules were formed via polyelectrolyte complex layer formation of PGU and poly-l-lysine, after which Ca2+, a cross-linker of PGU, was chelated, and this was accomplished by sequential immersion of microbeads in aqueous solutions of poly-l-lysine and sodium citrate. The encapsulated HepG2 cells proliferated and formed cell aggregates within the microparticles over a 14-day culture, with significantly larger aggregates forming within the microcapsules. Our results provide evidence for the viability of PGU for cell microencapsulation for the first time, thereby contributing to advancements in tissue engineering.

Trends in teicoplanin loading dose implementation from 2010 to 2019 and evaluation of safety and efficacy factors: a retrospective cohort study based on a Japanese administrative claims database.

BACKGROUND: The loading dose of teicoplanin (TEIC) is recommended for implementation. However, there is significant discrepancy between the dose settings in the package insert and, in the guidelines, and the actual status of loading doses in Japan is unclear. Furthermore, TEIC causes liver injury as side effect. Although the risk of developing liver injury has not been reported to be increased following a loading dose based on the guidelines, there is a lack of reports in large populations. Therefore, we evaluated the trend in the loading dose and factors affecting the efficacy and safety of TEIC administration. METHODS: A Japanese administrative claims database was used in this study. Trends in loading doses were evaluated in target populations administered TEIC between 2010 and 2019. Patient characteristics were adjusted by propensity score matching based on the guideline group (total dose of 3 days > 1,600 mg) and non-guideline group (≤ 1,600 mg) of the loading dose. Finally, univariable and multivariable conditional logistic regression analysis was performed to evaluate factors affecting 30-day mortality and liver injury. RESULTS: A total of 10,030 patients were selected based on these criteria. The proportion of loading doses based on the recommended guidelines showed an increase over time, regardless of the implementation of therapeutic drug monitoring (TDM), but especially so in cases where TDM was implemented, the loading doses were administered in accordance with the recommendations of the guidelines. Conditional logistic regression analysis showed a relationship between drug management and guidance fees (odds ratio [OR]: 0.45, 95% confidence interval [CI]: 0.36‒0.55), a reimbursement indicating pharmacist intervention, and a reduction in 30-day mortality. In addition, loading doses based on the recommended guidelines had no influence on liver injury, and other factors were not significantly associated with increased incidence of liver injury. CONCLUSION: Thus, this study implies the benefits of pharmacological management as indicated by drug management and guidance fee and supports the implementation of loading doses based on the guideline on TEIC administration.

Phenol-Grafted Alginate Sulfate Hydrogel as an Injectable FGF-2 Carrier.

In the field of tissue engineering, fibroblast growth factor-2 (FGF-2) effectively regenerates damaged tissue and restores its biological function. However, FGF-2 readily diffuses and degrades under physiological conditions. Therefore, methods for the sustained and localized delivery of FGF-2 are needed. Drug delivery systems using hydrogels as carriers have attracted significant interest. Injectable hydrogels with an affinity for FGF-2 are candidates for FGF-2 delivery systems. In this study, we fabricated a hydrogel from phenol-grafted alginate sulfate (AlgS-Ph) and investigated its application to the delivery of FGF-2. The hydrogel was prepared under mild conditions via horseradish peroxidase (HRP)-mediated cross-linking. Surface plasmon resonance (SPR) measurements show that the AlgS-Ph hydrogel has an affinity for FGF-2 in accordance with its degree of sulfation. Conditions for the preparation of the AlgS-Ph hydrogel, including HRP and H2O2 concentrations, are optimized so that the hydrogel can be used as an injectable drug carrier. The hydrogel shows no cytotoxicity when using 10T1/2 cells as a model cell line. The angiogenesis assay shows that FGF-2 released from the AlgS-Ph hydrogel promotes the formation of blood vessels. These results indicate that the AlgS-Ph hydrogel is a suitable candidate for the FGF-2 carrier.

Influence of pharmacists and infection control teams or antimicrobial stewardship teams on the safety and efficacy of vancomycin: A Japanese administrative claims database study.

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) has a high mortality and requires effective treatment with anti-MRSA agents such as vancomycin (VCM). Management of the efficacy and safety of VCM has been implemented with the assignment of pharmacists in hospital wards and the establishment of teams related to infectious diseases. However, there are no reports evaluating the association between these factors and the efficacy and safety of VCM in large populations. METHODS: This study used the Japanese administrative claims database accumulated from 2010 to 2019. The population was divided into two groups, therapeutic drug monitoring (TDM) group and non-TDM group, and adjusted by propensity score matching. We performed multivariate logistic regression analysis to determine the influence of pharmacists and infection control teams or antimicrobial stewardship teams on acute kidney injury (AKI) and 30-day mortality. RESULTS: The total number of patients was 73 478 (TDM group, n = 55 269; non-TDM group, n = 18 209). After propensity score matching, 18 196 patients were matched in each group. Multivariate logistic regression analysis showed that pharmacological management for each patient contributed to the reduction of AKI (odds ratio [OR]: 0.812, 95% confidence interval [CI]: 0.723‒0.912) and 30-day mortality (OR: 0.538, 95% CI: 0.503‒0.575). However, the establishment of infectious disease associated team in facilities and the assignment of pharmacists in the hospital wards had no effect on AKI and 30-day mortality. In addition, TDM did not affect the reduction in AKI (OR: 1.061, 95% CI: 0.948‒1.187), but reduced 30-day mortality (OR: 0.873, 95% CI: 0.821‒0.929). CONCLUSION: Pharmacologic management for individual patients, rather than assignment systems at facilities, is effective to reduce AKI and 30-day mortality with VCM administration.

Development of phenol-grafted polyglucuronic acid and its application to extrusion-based bioprinting inks.

In this present work, we developed a phenol grafted polyglucuronic acid (PGU) and investigated the usefulness in tissue engineering field by using this derivative as a bioink component allowing gelation in extrusion-based 3D bioprinting. The PGU derivative was obtained by conjugating with tyramine, and the aqueous solution of the derivative was curable through a horseradish peroxidase (HRP)-catalyzed reaction. From 2.0 w/v% solution of the derivative containing 5 U/mL HRP, hydrogel constructs were successfully obtained with a good shape fidelity to blueprints. Mouse fibroblasts and human hepatoma cells enclosed in the printed constructs showed about 95% viability the day after printing and survived for 11 days of study without a remarkable decrease in viability. These results demonstrate the great potential of the PGU derivative in tissue engineering field especially as an ink component of extrusion-based 3D bioprinting.

A laboratory study of hydraulic fracturing at the brittle-ductile transition.

Developing high-enthalpy geothermal systems requires a sufficiently permeable formation to extract energy through fluid circulation. Injection experiments above water's critical point have shown that fluid flow can generate a network of highly conductive tensile cracks. However, what remains unclear is the role played by fluid and solid rheology on the formation of a dense crack network. The decrease of fluid viscosity with temperature and the thermally activated visco-plasticity in rock are expected to change the deformation mechanisms and could prevent the formation of fractures. To isolate the solid rheological effects from the fluid ones and the associated poromechanics, we devise a hydro-fracture experimental program in a non-porous material, polymethyl methacrylate (PMMA). In the brittle regime, we observe rotating cracks and complex fracture patterns if a non-uniform stress distribution is introduced in the samples. We observe an increase of ductility with temperature, hampering the propagation of hydraulic fractures close to the glass transition temperature of PMMA, which acts as a limit for brittle fracture propagation. Above the glass transition temperature, acoustic emission energy drops of several orders of magnitude. Our findings provide a helpful guidance for future studies of hydro-fracturing of supercritical geothermal systems.