Immunoglobulin G4 -related gastrointestinal disease associated with type 1 autoimmune pancreatitis: A case report.

Immunoglobulin G4 (IgG4)-related diseaseis a systemic inflammatory condition of unknown etiology characterized by increases in serum IgG4 and in the number of IgG4-positive cells in affected tissues. One of the commonly involved locations is the pancreas; this condition is known as type 1 autoimmune pancreatitis (AIP). Type 1 AIP, which shows a biliary stricture in the intrapancreatic bile duct, can be misdiagnosed as a malignancy due to similar cholangiography findings and clinical presentation. In rare cases complicated by post-bulbar duodenal ulcers, differentiating between type 1 AIP and malignancies is even more difficult. An 81-year-old male was referred to our hospital for the treatment of a pancreatic head mass and obstructive jaundice. Serological and radiological findings were consistent with both type 1 AIP and a malignancy. Gastroduodenoscopy revealed a post-bulbar duodenal ulcer with endoscopic features that evoked malignant duodenal invasion. Although biopsies were negative for malignant cells, subsequent bleeding from the lesion suggested the progression of malignancy, which led to surgical resection. Pancreatoduodenectomy and pathological examination indicated that type 1 AIP was present. Simultaneously, the involvement of IgG4-related disease in the ulcerative lesion was suggested. To our knowledge, this is the first reported case of type 1 AIP complicated by post-bulbar duodenal ulcers, which was misdiagnosed as malignancy and considered an IgG4-related gastrointestinal disease associated with type 1 AIP.

Clinical impact of the use of chronic suppressive antibiotics against recurrent ventricular assist device infections.

Ventricular assist device (VAD) infections are frequent causes of hospital readmission. The risk factors and optimal preventive strategies for such, including chronic suppressive antibiotics (CSA), remain uncertain. We performed a single-center, retrospective, observational cohort study assessing continuous flow VAD recipients who underwent implantation between 2008 and 2018 in Japan. From primary VAD infection (VADI), we followed the patients for recurrent infection, defined as relapsing VAD-specific (e.g., localized infections) or VAD-related (e.g., bacteremia) infections requiring hospital readmission. CSA was defined as the use of oral antimicrobial agents continued beyond initial antibiotic use until transplantation, VAD withdrawal, VADI recurrence, or death. Survival analysis was performed to identify risk factors for recurrent infection accounting for competing risks (e.g., deaths and transplants). Among 163 eligible patients, 76 patients had VADIs. The main causative organism in primary VADI was Staphylococcus aureus (63%, 48/76). Among them, 41 had recurrent infections, whereas 35 had none during the follow-up period (median, 335 days). Thirty-six patients received CSA for a median of 478 days. Although CSA was associated with a decreased risk of recurrent infection [adjusted sub-distribution hazard ratio (SHR), 0.40; 95% confidence interval (CI), 0.18-0.89; P = 0.03], this protective effect was observed only after primary VAD-specific infection (SHR, 0.28; 95% CI, 0.12-0.64; P < 0.01) but not after VAD-related infection. Surgical procedures during primary VADI were associated with an increased risk (SHR, 2.00; 95% CI, 1.10-3.66; P = 0.02). One patient had an adverse drug reaction. CSA may be an effective approach to limit relapsing VADIs following a primary VAD-specific infection with minimal adverse events. IMPORTANCE: Ventricular assist device infections (VADIs) are a significant complication leading to hospital readmissions. However, the risk factors and optimal preventive strategies for VADI remain unclear. This study investigated the effectiveness of chronic suppressive antibiotic therapy in patients with VADI. We found that the use of chronic suppressive antibiotic therapy was associated with a reduction in the risk of VADI recurrence with few adverse reactions. Our findings suggest the potential benefit of chronic suppressive antibiotics in preventing infections in selected cases. Our findings are relevant for the management of patients with ventricular assist devices awaiting heart transplantation, providing valuable insights for clinical practice.

Thiamine deficiency as a differential diagnosis for severe fatigue in terminally ill cancer patients.

OBJECTIVES: Patients with advanced cancer present various symptoms as their disease progresses. Among these, fatigue is a frequent symptom in patients with advanced cancer and is associated with decreased quality of life (QOL). However, there are few reports regarding its association with thiamine deficiency (TD). METHODS: We report a case in which we found TD in a patient with advanced lung cancer who presented with weight loss, significant fatigue, and appeared to have a worsening general condition, for whom symptoms were dramatically improved within a short period of time by intravenous administration of thiamine. RESULTS: The patient was a 76-year-old woman who had been diagnosed with lung cancer and liver metastases 6 months earlier. Due to interstitial pneumonia, she was not a candidate for chemotherapy and so palliative care was started. At 8 months after initial diagnosis, the patient complained of fatigue during a medical examination, so a blood sample was taken. A week later, she visited the hospital with a cane. She felt extremely fatigued and was unable to stand, but results from the previous blood test revealed that a TD. The fatigue disappeared 15 minutes after intravenous administration of thiamine and she was able to return home without the cane. SIGNIFICANCE OF RESULTS: Fatigue is a frequent symptom in advanced cancer patients, and TD may be the underlying cause. Inclusion of TD in the differential diagnosis may contribute to improving patient QOL.

Carbon dioxide-dependent, extended-spectrum ß-lactamase producing Escherichia coli bacteremia associated with pyelonephritis: A case-report.

Escherichia coli is a facultative anaerobic bacterium that causes urinary tract and bloodstream infections. Generally, E. coli is easily identified in routine clinical microbiology laboratories. Herein, we report a case of pyelonephritis with bacteremia due to extended-spectrum ß-lactamase (ESBL) producing E. coli, which delayed the identification of the isolate as it exhibited carbon dioxide (CO2)-dependent growth. The patient was a 62-year-old man who presented with nausea and an altered mental status. Contrast-enhanced computed tomography revealed multiple abscesses in the left kidney. The anaerobic bottles of the two sets of blood cultures were positive, but growth on a routine aerobic culture was weak. Identification of the isolate was delayed because it grew only on agar plates incubated in a 5 % CO2 atmosphere. The isolate was suspected to be an ESBL-producing strain based on antimicrobial susceptibility testing, which was confirmed by polymerase chain reaction analysis. The patient was successfully treated with administering meropenem and nephrectomy. To the best-of-our-knowledge, this is the first reported case of a human infection caused by ESBL-producing carbon-dioxide-dependent E. coli.

Engineered protein subunit COVID19 vaccine is as immunogenic as nanoparticles in mouse and hamster models.

Initial studies on the immunogenicity of SARS-CoV-2 (CoV-2) S glycoprotein ("spike") as a protein subunit vaccine suggested sub-optimal efficacy in mammals. Although protein engineering efforts have produced CoV-2 spike protein sequences with greatly improved immunogenicity, additional strategies for improving the immunogenicity of CoV-2 protein subunit vaccines are scaffolding and the use of adjuvants. Comparisons of the effectiveness of engineered protein-only and engineered protein-nanoparticles vaccines have been rare. To explore this knowledge gap, we inoculated mice with two doses of either sequence-optimized trimeric spike protein or one of several sequence-optimized spike nanoparticles. We measured their immune response up to two months after the first dose. We also measured the immune response and protection against live virus in hamsters inoculated with either sequence-optimized trimeric spike protein or a liposome-based sequence-optimized spike nanoparticle. We found that in the presence of adjuvant, the antibody and neutralization titers elicited by spike-nanoparticles were not significantly greater than those elicited by spike-only in mice, even at doses as low as 0.1 µg/animal. Hamsters vaccinated with spike-only or spike-nanoparticles were equally protected from live virus one month after their first inoculation. These results suggest that sequence-optimized protein subunit vaccines in the form of individual prefusion-stabilized trimers can be as effective in improving immunogenicity as scaffolded forms.

How can heatstroke damage the brain? A mini review.

Record-breaking heat waves over the past 20 years have led to a global increase in heat-related deaths, including heatstroke. Heat-related illnesses occur when the body cannot adapt to the elevated temperatures in the environment, leading to various symptoms. In severe situations, such as heatstroke, the body temperature can rise above 40°C, leading to significant injury to body systems, with particular susceptibility of the central nervous system (CNS). Neuroimaging studies conducted months or years after a heatstroke have revealed cellular damage in the cerebellum and other brain regions, including the hippocampus, midbrain, and thalamus, with the potential for long-term neurological complications in survivors of a heatstroke. This mini review aimed to describe the mechanisms and pathways underlying the development of brain injury induced by heatstroke and identify diagnostic imaging tools and biomarkers for injury to the CNS due to a heatstroke.

Comparative and experimental pathology of passaged Newcastle disease virus isolates in ducks.

Although waterfowl are less susceptible to Newcastle disease (ND) virus (NDV) infection compared with chickens and turkeys, lethal ND in waterfowl has been sporadically reported. Factors underlying the high pathogenicity of certain NDV strains in waterfowl remain unclear. In ducks, the NDV 9a5b isolate shows low pathogenicity while the d5a20b isolate shows high pathogenicity. This study aimed to identify the definitive lesions that led to the lethal virulence of d5a20b by comparing the histopathology of 9a5b- or d5a20b-inoculated ducks in order to elucidate lesions related to the enhanced pathogenicity of certain NDV strains in ducks. Herein, 7-day-old ducks were intranasally inoculated with either 9a5b or d5a20b NDV strains. The neurological signs were more severe in the d5a20b-inoculated group than in the 9a5b-inoculated group. Ducks in the d5a20b-inoculated group exhibited more severe lymphoid depletion in immune organs than those in the 9a5b-inoculated group, which may have caused an immunosuppressive state in the d5a20b-inoculated ducks. Ducks in the d5a20b-inoculated group had more severe nonsuppurative encephalitis with increased NDV nucleoprotein than those in the 9a5b-inoculated group. Additionally, pancreatic necrosis, with intralesional NDV nucleoprotein, was more severe in the d5a20b-inoculated group than in the 9a5b-inoculated group. Our results showed that the immune organs, brain, and pancreas were significant targets of the NDV d5a20b infection in ducks.

The influence of revised ordinance on radiation protection management in Japanese hospitals: device deployment and involvement of radiology technologists.

PURPOSE: This study evaluates the impact of the 2021 revision of Japan's Ordinance on the Prevention of Ionizing Radiation Hazards on radiation protection practices, focusing on the deployment of radiation protection devices and the involvement of radiology technologists in Japanese hospitals. METHODS: A two-phase web-based questionnaire survey was conducted among hospitals registered as training facilities with the Japanese Radiological Society. The survey included 53 questions covering facility information, radiation worker management, training, and working environment. RESULTS: The use of lens-specific dosimeters significantly increased post-revision (p = 0.005). Protective eyewear availability showed minor improvements, particularly in angiographic rooms (p = 0.019). The involvement of radiology technologists remained high in angiographic rooms but showed no significant changes in endoscopy and fluoroscopy rooms. Larger hospitals exhibited better compliance with protective measures, though gaps in resource allocation persisted. CONCLUSION: The ordinance revision led to significant improvements in dosimeter usage but only minor changes in protective eyewear deployment and technologist involvement.

Incidence and risk factors of hypotension-related adverse events among Japanese patients with heart failure receiving sacubitril/valsartan or enalapril: Results from the PARALLEL-HF study.

BACKGROUND: The PARALLEL-HF trial showed that treatment with sacubitril/valsartan resulted in more symptomatic hypotension versus enalapril in Japanese patients with heart failure (HF) and reduced ejection fraction, similar to PARADIGM-HF. Use of sacubitril/valsartan in these patients may be limited by concerns regarding hypotension. METHODS: This post-hoc analysis characterized hypotension-related adverse events (AEs) and their effects on efficacy using data from PARALLEL-HF, in which patients received sacubitril/valsartan 200 mg twice daily or enalapril 10 mg twice daily. RESULTS: Of 223 patients, 28.2 % experienced hypotension-related AEs and incidence was higher with sacubitril/valsartan versus enalapril (hazard ratio, 2.2; 95 % CI, 1.3-3.8; p = 0.0027). However, reduction in mean systolic blood pressure from baseline to study end did not significantly differ (sacubitril/valsartan: -2.2 mmHg vs enalapril: -1.3 mmHg; p = 0.6895). Patients who experienced hypotension-related AEs had lower mean body mass index, higher median N-terminal pro-brain natriuretic peptide at randomization, and more frequent history of stroke. Hypotension-related AEs leading to treatment discontinuation were not significantly different for sacubitril/valsartan versus enalapril (3.4 % vs 6.9 %, p = 0.5957). Reduction in risk of cardiovascular death or HF hospitalization was similar with sacubitril/valsartan versus enalapril in patients with or without hypotension-related AEs. CONCLUSIONS: Incidence of hypotension-related AEs was higher in the sacubitril/valsartan versus enalapril group but did not affect risk of cardiovascular death or HF hospitalization, which was similar between treatment groups.

Effect of Semaglutide on Cardiac Structure and Function in Patients With Obesity-Related Heart Failure.

BACKGROUND: Obesity is associated with adverse cardiac remodeling and is a key driver for the development and progression of heart failure (HF). Once-weekly semaglutide (2.4 mg) has been shown to improve HF-related symptoms and physical limitations, body weight, and exercise function in patients with obesity-related heart failure with preserved ejection fraction (HFpEF), but the effects of semaglutide on cardiac structure and function in this population remain unknown. OBJECTIVES: In this echocardiography substudy of the STEP-HFpEF Program, we evaluated treatment effects of once-weekly semaglutide (2.4 mg) vs placebo on cardiac structure and function. METHODS: Echocardiography at randomization and 52 weeks was performed in 491 of 1,145 participants (43%) in the STEP-HFpEF Program (pooled STEP-HFpEF [Semaglutide Treatment Effect in People with Obesity and HFpEF] and STEP-HFpEF DM [Semaglutide Treatment Effect in People with Obesity, HFpEF, and Type 2 Diabetes] trials). The prespecified primary outcome was change in left atrial (LA) volume, with changes in other echocardiography parameters evaluated as secondary outcomes. Treatment effects of semaglutide vs placebo were assessed using analysis of covariance stratified by trial and body mass index, with adjustment for baseline parameter values. RESULTS: Overall, baseline clinical and echocardiographic characteristics were balanced among those receiving semaglutide (n = 253) and placebo (n = 238). Between baseline and 52 weeks, semaglutide attenuated progression of LA remodeling (estimated mean difference [EMD] in LA volume, -6.13 mL; 95% CI: -9.85 to -2.41 mL; P = 0.0013) and right ventricular (RV) enlargement (EMD in RV end-diastolic area: -1.99 cm2; 95% CI: -3.60 to -0.38 cm2; P = 0.016; EMD in RV end-systolic area: -1.41 cm2; 95% CI: -2.42 to -0.40] cm2; P = 0.0064) compared with placebo. Semaglutide additionally improved E-wave velocity (EMD: -5.63 cm/s; 95% CI: -9.42 to -1.84 cm/s; P = 0.0037), E/A (early/late mitral inflow velocity) ratio (EMD: -0.14; 95% CI: -0.24 to -0.04; P = 0.0075), and E/e' (early mitral inflow velocity/early diastolic mitral annular velocity) average (EMD: -0.79; 95% CI: -1.60 to 0.01; P = 0.05). These associations were not modified by diabetes or atrial fibrillation status. Semaglutide did not significantly affect left ventricular dimensions, mass, or systolic function. Greater weight loss with semaglutide was associated with greater reduction in LA volume (Pinteraction = 0.033) but not with changes in E-wave velocity, E/e' average, or RV end-diastolic area. CONCLUSIONS: In the STEP-HFpEF Program echocardiography substudy, semaglutide appeared to improve adverse cardiac remodeling compared with placebo, further suggesting that treatment with semaglutide may be disease modifying among patients with obesity-related HFpEF. (Research Study to Investigate How Well Semaglutide Works in People Living With Heart Failure and Obesity [STEP-HFpEF]; NCT04788511; Research Study to Look at How Well Semaglutide Works in People Living With Heart Failure, Obesity and Type 2 Diabetes [STEP-HFpEF DM]; NCT04916470).

Influenza Vaccination and Cardiovascular Events in Japanese Patients With Heart Failure　- Findings From the PARALLEL-HF Trial.

Background: Influenza is associated with an increased risk for cardiovascular events in patients with heart failure (HF). This study aimed to investigate the prevalence of influenza vaccination among Japanese patients with HF enrolled in the PARALLEL-HF (Prospective comparison of ARNI with ACEi to determine the noveL beneficiaL trEatment vaLue in Japanese Heart Failure patients) trial and the association between receiving influenza vaccination and cardiovascular events including death or HF hospitalization. Methods and Results: In PARALLEL-HF, in which 223 patients with HF and reduced ejection fraction (HFrEF) were randomized to the angiotensin-receptor neprilysin inhibitor (sacubitril/valsartan) or enalapril, 97 (43%) received influenza vaccination. Influenza vaccination tended to be associated, though statistically not significant, with a lower risk for all-cause death (adjusted hazard ratio [HR]: 0.67; 95% confidence interval [CI]: 0.32-1.39) and cardiopulmonary or influenza-related hospitalization or death (adjusted HR: 0.72; 95% CI: 0.46-1.11) in propensity score-adjusted models. Conclusions: The influenza vaccination rate in Japanese patients with HFrEF who were well managed on guideline-directed medical therapy was suboptimal despite recommendations from clinical practice guidelines. However, importantly, it could be associated with better clinical benefits.

Effects of probiotics on sleep parameters: A systematic review and meta-analysis.

AIM: Although sleep is essential for maintaining good health and well-being, sleep disorders are becoming increasingly prevalent. Probiotics may play a role in sleep regulation; therefore, this study aimed to provide a comprehensive overview of the effects of probiotics on sleep parameters. METHODS: We conducted a systematic literature review and meta-analysis, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses methodology. Relevant placebo-controlled randomized controlled trials examining the effects of probiotics on sleep outcomes were identified through systematic searches in the PubMed, Cochrane Library, and Ichushi databases. Data were extracted from eligible studies and the risk of bias was assessed. Statistical analyses were performed to assess the effects of probiotics on various sleep-related variables. RESULTS: Fifteen randomized controlled trials were included in this review. The decrease in Pittsburgh Sleep Quality Index (PSQI) scores in the probiotics group was significantly lower than that in the placebo group after 4-6 weeks and 8-16 weeks, indicating improved sleep quality. The Oguri-Shirakawa-Azumi (OSA) sleep inventory score was also decreased in the probiotics group for Factor 1 "sleepiness on rising" and Factor 4 "refreshing," indicating improved sleep quality. Some studies however, showed a risk of bias. CONCLUSION: This systematic review and meta-analysis indicated that probiotics may improve sleep quality, as measured by the PSQI and OSA sleep inventory. However, further research is needed to better understand the effects of probiotics on specific sleep parameters and address the limitations of existing studies.

Bacterial sepsis causes more dramatic pathogenetic changes in the Th1 pathway than does viral (COVID-19) sepsis: a prospective observational study of whole blood transcriptomes.

OBJECTIVES: This study aimed to comprehensively compare host responses of patients with bacterial sepsis and those with viral (COVID-19) sepsis by analyzing messenger RNA (mRNA) and microRNA (miRNA) profiles to shed light on their distinct pathophysiological mechanisms. DESIGN: Prospective observational study. SETTING: Whole blood RNA sequencing was used to analyze mRNA and miRNA profiles of patients diagnosed as having bacterial sepsis or viral (COVID-19) sepsis at the Department of Trauma and Emergency Medicine, Osaka University Graduate School of Medicine. PATIENTS: Twenty-two bacterial sepsis patients, 35 viral (COVID-19) sepsis patients, and 15 healthy subjects admitted to the department were included. We diagnosed bacterial sepsis patients according to the sepsis-3 criterion that the Sequential Organ Failure Assessment score must increase to 2 points or more among patients with suspected infections. Viral (COVID-19) sepsis patients were diagnosed using SARS-CoV-2 RT-PCR testing, and presence of pneumonia was assessed through chest computed tomography scans. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: For RNA sequencing, 14,500 mRNAs, 1121 miRNAs, and 2556 miRNA-targeted mRNAs were available for analysis in the bacterial sepsis patients. Numbers of genes showing upregulated: downregulated gene expression (false discovery rate < 0.05, |log2 fold change| > 1.5) were 256:2887 for mRNA, 53:5 for miRNA, and 49:2507 for miRNA-targeted mRNA. Similarly, in viral (COVID-19) sepsis patients, 14,500 mRNAs, 1121 miRNAs, and 327 miRNA-targeted mRNAs were analyzed, with numbers of genes exhibiting upregulated: downregulated gene expression of 672:1147 for mRNA, 3:4 for miRNA, and 165:162 for miRNA-targeted mRNA. This analysis revealed significant differences in the numbers of upregulated and downregulated genes expressed and pathways between the bacterial sepsis and viral (COVID-19) sepsis patients. Bacterial sepsis patients showed activation of the PD-1 and PD-L1 cancer immunotherapy signaling pathway and concurrent suppression of Th1 signaling. CONCLUSION: Our study illuminated distinct molecular variances between bacterial sepsis and viral (COVID-19) sepsis. Bacterial sepsis patients had a greater number of upregulated and downregulated genes and pathways compared to viral (COVID-19) sepsis patients. Especially, bacterial sepsis caused more dramatic pathogenetic changes in the Th1 pathway than did viral (COVID-19) sepsis.

Impact of Serum Indoxyl Sulfate on One-Year Adverse Events in Chronic Kidney Disease Patients with Heart Failure.

Background/Objectives: Indoxyl sulfate, a uremic toxin, is associated with mortality and cardiovascular events in patients with chronic kidney disease (CKD). This study aimed to evaluate the prognostic implications of serum indoxyl sulfate levels in patients with heart failure and CKD. Methods and Results: This was a prospective multicenter observational study. Overall, 300 patients with chronic heart failure with a previous history of hospitalization and an estimated glomerular filtration rate (eGFR) of 45 mL/min/1.73 m2 or less (CKD stage G3b to G5) without dialysis were analyzed. The primary outcome assessed in a time-to-event analysis from the measurement of indoxyl sulfate was a composite of all-cause death, hospitalization for heart failure, nonfatal myocardial infarction, and nonfatal stroke. Clinical events were followed-up to one year after indoxyl sulfate measurement. The median patient age was 75 years, and 57% of the patients were men. We divided the cohort into low and high indoxyl sulfate categories according to a median value of 9.63 mg/mL. The primary outcome occurred in 27 of 150 patients (18.0%) in the low indoxyl sulfate group and 27 of 150 patients (18.0%) in the high indoxyl sulfate group (hazard ratio, 1.00; 95% confidence interval, 0.58 to 1.70, p = 0.99). In the post hoc exploratory analyses, the results were consistent across age, sex, body mass index, left ventricular ejection fraction, eGFR, and N-terminal pro b-type natriuretic peptide. Conclusions: Among heart failure patients with CKD stages G3b to 5G, serum indoxyl sulfate concentrations were not significantly associated with the subsequent occurrence of cardiovascular events.

Atypical and non-classical CD45RBlo memory B cells are the majority of circulating SARS-CoV-2 specific B cells following mRNA vaccination or COVID-19.

Resting memory B cells can be divided into classical or atypical groups, but the heterogenous marker expression on activated memory B cells makes similar classification difficult. Here, by longitudinal analysis of mass cytometry and CITE-seq data from cohorts with COVID-19, bacterial sepsis, or BNT162b2 mRNA vaccine, we observe that resting B cell memory consist of classical CD45RB+ memory and CD45RBlo memory, of which the latter contains of two distinct groups of CD11c+ atypical and CD23+ non-classical memory cells. CD45RB levels remain stable in these cells after activation, thereby enabling the tracking of activated B cells and plasmablasts derived from either CD45RB+ or CD45RBlo memory B cells. Moreover, in both COVID-19 patients and mRNA vaccination, CD45RBlo B cells formed the majority of SARS-CoV2 specific memory B cells and correlated with serum antibodies, while CD45RB+ memory are activated by bacterial sepsis. Our results thus identify that stably expressed CD45RB levels can be exploited to trace resting memory B cells and their activated progeny, and suggest that atypical and non-classical CD45RBlo memory B cells contribute to SARS-CoV-2 infection and vaccination.

Cocirculation of Genetically Distinct Highly Pathogenic Avian Influenza H5N5 and H5N1 Viruses in Crows, Hokkaido, Japan.

We isolated highly pathogenic avian influenza (HPAI) H5N5 and H5N1 viruses from crows in Hokkaido, Japan, during winter 2023-24. They shared genetic similarity with HPAI H5N5 viruses from northern Europe but differed from those in Asia. Continuous monitoring and rapid information sharing between countries are needed to prevent HPAI virus transmission.

Enhanced Marine Biodegradation of Polycaprolactone through Incorporation of Mucus Bubble Powder from Violet Sea Snail as Protein Fillers.

Microplastics' spreading in the ocean is currently causing significant damage to organisms and ecosystems around the world. To address this oceanic issue, there is a current focus on marine degradable plastics. Polycaprolactone (PCL) is a marine degradable plastic that is attracting attention. To further improve the biodegradability of PCL, we selected a completely new protein that has not been used before as a functional filler to incorporate it into PCL, aiming to develop an environmentally friendly biocomposite material. This novel protein is derived from the mucus bubbles of the violet sea snail (VSS, Janthina globosa), which is a strong bio-derived material that is 100% degradable in the sea environment by microorganisms. Two types of PCL/bubble composites, PCL/b1 and PCL/b5, were prepared with mass ratios of PCL to bubble powder of 99:1 and 95:5, respectively. We investigated the thermal properties, mechanical properties, biodegradability, surface structure, and crystal structure of the developed PCL/bubble composites. The maximum biochemical oxygen demand (BOD) degradation for PCL/b5 reached 96%, 1.74 times that of pure PCL (≈55%), clearly indicating that the addition of protein fillers significantly enhanced the biodegradability of PCL. The surface morphology observation results through scanning electron microscopy (SEM) definitely confirmed the occurrence of degradation, and it was found that PCL/b5 underwent more significant degradation compared to pure PCL. The water contact angle measurement results exhibited that all sheets were hydrophobic (water contact angle > 90°) before the BOD test and showed the changes in surface structure after the BOD test due to the newly generated indentations on the surface, which led to an increase in surface toughness and, consequently, an increase in surface hydrophobility. A crystal structure analysis by wide-angle X-ray scattering (WAXS) discovered that the amorphous regions were decomposed first during the BOD test, and more amorphous regions were decomposed in PCL/b5 than in PCL, owing to the addition of the bubble protein fillers from the VSS. The differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA) results suggested that the addition of mucus bubble protein fillers had only a slight impact on the thermal properties of PCL. In terms of mechanical properties, compared to pure PCL, the mucus-bubble-filler-added composites PCL/b1 and PCL/b5 exhibited slightly decreased values. Although the biodegradability of PCL was significantly improved by adding the protein fillers from mucus bubbles of the VSS, enhancing the mechanical properties at the same time poses the next challenging issue.