Chronic Postsurgical Pain Following Lung Transplantation: Characteristics, Risk Factors, Treatment, and Prevention: A Narrative Review.

Chronic pain after lung transplantation (LTx) can substantially reduce quality of life (QoL), yet current consensus guidelines say little about how to prevent or manage it. Research on pain after LTx has tended to focus on acute rather than chronic pain, and it has not extensively examined the factors associated with onset or resolution of chronic pain, which differ from factors influencing chronic pain after general thoracic surgery. This narrative review explores what is known about the epidemiology and risk factors of chronic pain after LTx, as well as effective ways to treat or prevent it. The review identifies key questions and issues that should be the focus of future research.

Predictive modeling for identifying infection risk following spinal surgery: Optimizing patient management.

Infection is known to occur in a substantial proportion of patients following spinal surgery and predictive modeling may provide a useful means for identifying those at higher risk of complications and poor prognosis, which could help optimize pre- and postoperative management strategies. The outcome measure of the present study was to investigate the occurrence of all-cause infection during hospitalization following scoliosis surgery. To meet this aim, the present study retrospectively analyzed 370 patients who underwent surgery at the Second Affiliated Hospital, Zhejiang University School of Medicine (Hangzhou, China) between January 2016 and October 2022, and patients who either experienced or did not experience all-cause infection while in hospital were compared in terms of their clinicodemographic characteristics, surgical variables and laboratory test results. Logistic regression was subsequently applied to data from a subset of patients in order to build a model to predict infection, which was validated using another subset of patients. All-cause, in-hospital postoperative infections were found to have occurred in 66/370 patients (17.8%). The following variables were included in a predictive model: Sex, American Society of Anesthesiologists (ASA) classification, body mass index (BMI), diabetes mellitus, hypertension, preoperative levels of white blood cells and preoperative C-reactive protein (CRP) and duration of surgery. The model exhibited an area under the curve of 0.776 against the internal validation set. In conclusion, dynamic nomograms based on sex, ASA classification, BMI, diabetes mellitus, hypertension, preoperative levels of white blood cells and CRP and duration of surgery may have the potential to be a clinically useful predictor of all-cause infection following scoliosis. The predictive model constructed in the present study may potentially facilitate the real-time visualization of risk factors associated with all-cause infection following surgical procedures.

Nomogram for predicting postoperative pulmonary complications in spinal tumor patients.

OBJECTIVES: Although several independent risk factors for postoperative pulmonary complications (PPCs) after spinal tumor surgery have been studied, a simple and valid predictive model for PPC occurrence after spinal tumor surgery has not been developed. PATIENTS AND METHODS: We collected data from patients who underwent elective spine surgery for a spinal tumor between 2013 and 2020 at a tertiary hospital in China. Data on patient characteristics, comorbidities, preoperative examinations, intraoperative variables, and clinical outcomes were collected. We used univariable and multivariable logistic regression models to assess predictors of PPCs and developed and validated a nomogram for PPCs. We evaluated the performance of the nomogram using the area under the receiver operating characteristic curve (ROC), calibration curves, the Brier Score, and the Hosmer-Lemeshow (H-L) goodness-of-fit test. For clinical use, decision curve analysis (DCA) was conducted to identify the model's performance as a tool for supporting decision-making. RESULTS: Among the participants, 61 (12.4%) individuals developed PPCs. Clinically significant variables associated with PPCs after spinal tumor surgery included BMI, tumor location, blood transfusion, and the amount of blood lost. The nomogram incorporating these factors showed a concordance index (C-index) of 0.755 (95% CI: 0.688-0.822). On internal validation, bootstrapping with 1000 resamples yielded a bias-corrected area under the receiver operating characteristic curve of 0.733, indicating the satisfactory performance of the nomogram in predicting PPCs. The calibration curve demonstrated accurate predictions of observed values. The decision curve analysis (DCA) indicated a positive net benefit for the nomogram across most predicted threshold probabilities. CONCLUSIONS: We have developed a new nomogram for predicting PPCs in patients who undergo spinal tumor surgery.

Risk Factors for Hypocoagulability After Cardiac Surgery: A Retrospective Study.

Hemostatic disturbances after cardiac surgery can lead to excessive postoperative bleeding. Thromboelastography (TEG) was employed to evaluate perioperative coagulative alterations in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB), investigating the correlation between factors concomitant with cardiac surgery and modifications in coagulation. Coagulation index as determined by TEG correlated significantly with postoperative bleeding at 24-72 h after cardiac surgery (P < .001). Among patients with a normal preoperative coagulation index, those with postoperative hypocoagulability showed significantly lower nadir temperature (P = .003), larger infused fluid volume (P = .003), and longer CPB duration (P = .033) than those with normal coagulation index. Multivariate logistic regression showed that nadir intraoperative temperature was an independent predictor of postoperative hypocoagulability (adjusted OR: 0.772, 95% CI: 0.624-0.954, P = .017). Multivariate linear regression demonstrated linear associations of nadir intraoperative temperature (P = .017) and infused fluid volume (P = .005) with change in coagulation index as a result of cardiac surgery. Patients are susceptible to hypocoagulability after cardiac surgery, which can lead to increased postoperative bleeding. Ensuring appropriate temperature and fluid volume during cardiac surgery involving CPB may reduce risk of postoperative hypocoagulability and bleeding.

Causal relationship between obesity and iron deficiency anemia: a two-sample Mendelian randomization study.

Background: Observational studies have suggested an association between obesity and iron deficiency anemia, but such studies are susceptible to reverse causation and residual confounding. Here we used Mendelian randomization to assess whether the association might be causal. Methods: Data on single-nucleotide polymorphisms that might be associated with various anthropometric indicators of obesity were extracted as instrumental variables from genome-wide association studies in the UK Biobank. Data on genetic variants in iron deficiency anemia were extracted from a genome-wide association study dataset within the Biobank. Heterogeneity in the data was assessed using inverse variance-weighted regression, Mendelian randomization Egger regression, and Cochran's Q statistic. Potential causality was assessed using inverse variance-weighted, Mendelian randomization Egger, weighted median, maximum likelihood and penalized weighted median methods. Outlier SNPs were identified using Mendelian randomization PRESSO analysis and "leave-one-out" analysis. Results: Inverse variance-weighted regression associated iron deficiency anemia with body mass index, waist circumference, trunk fat mass, body fat mass, trunk fat percentage, and body fat percentage (all odds ratios 1.003-1.004, P ≤ 0.001). Heterogeneity was minimal and no evidence of horizontal pleiotropy was found. Conclusion: Our Mendelian randomization analysis suggests that obesity can cause iron deficiency anemia.

Advance in the Polymerization Strategy for the Synthesis of ß-Peptides and ß-Peptoids.

Peptide mimics, possessing excellent biocompatibility and protease stability, have attracted broad attention and research in the biomedical field. ß-Peptides and ß-peptoids, as two types of vital peptide mimics, have demonstrated great potential in the field of foldamers, antimicrobials and protein binding, etc. Currently, the main synthetic strategies for ß-peptides and ß-peptoids include solid-phase synthesis and polymerization. Among them, polymerization in one-pot can minimize the repeated separation and purification used in solid-phase synthesis, and has the advantages of high efficiency and low cost, and can synthesize ß-peptides and ß-peptoids with high molecular weight. This review summarizes the polymerization methods for ß-peptides and ß-peptoids. Moreover, future developments of the polymerization method for the synthesis of ß-peptides and ß-peptoids will be discussed.

Advance in Hybrid Peptides Synthesis.

Hybrid peptides with heterogeneous backbone are a class of peptide mimics with adjustable proteolytic stability obtained from incorporating unnatural amino acid residues into peptide backbone. α/ß-peptides and peptide/peptoid hybrids are two types of hybrid peptides that are widely studied for diverse applications, and several synthetic methods have been developed. In this mini review, the advance in hybrid peptide synthesis is summarized, including solution-phase method, solid-phase method, and novel polymerization method. Conventional solution-phase method and solid-phase method generally result in oligomers with defined sequences, while polymerization methods have advantages in preparing peptide hybrid polymers with high molecular weight with simple operation and low cost. In addition, the future development of polymerization method to realize the control of the peptide hybrid polymer sequence is discussed.

Host defense peptide mimicking cyclic peptoid polymers exerting strong activity against drug-resistant bacteria.

Extensive use of antibiotics accelerates the emergence of drug-resistant bacteria and related infections. Host defense peptides (HDPs) have been studied as promising and potential therapeutic candidates. However, their clinical applications of HDPs are limited due to their high cost of synthesis and low stability upon proteolysis. Therefore, HDP mimics have become a new approach to address the challenge of bacterial resistance. In this work, we design the amphiphilic peptoid polymers by mimicking the positively charged and hydrophobic structures of HDPs and synthesize a series of cyclic peptoid polymers efficiently via the polymerization on α-amino acid N-substituted glycine N-carboxyanhydrides (α-NNCAs) using 1,8-diazabicycloundec-7-ene (DBU) as the initiator. The optimal cyclic peptoid polymer, poly(Naeg0.7Npfbg0.3)20, displays strong antibacterial activities against drug-resistant bacteria, but low hemolysis and cytotoxicity. In addition, the mode-of-action study indicates that the antibacterial mechanism is associated with bacterial membrane interaction. Our study implies that HDP mimicking cyclic peptoid polymers have potential application in treating drug-resistant bacterial infections.

Short Guanidinium-Functionalized Poly(2-oxazoline)s Displaying Potent Therapeutic Efficacy on Drug-Resistant Fungal Infections.

New antifungals are urgently needed to combat invasive fungal infections, due to limited types of available antifungal drugs and frequently encountered side effects, as well as the quick emergence of drug-resistance. We previously developed amine-pendent poly(2-oxazoline)s (POXs) as synthetic mimics of host defense peptides (HDPs) to have antibacterial properties, but with poor antifungal activity. Hereby, we report the finding of short guanidinium-pendent POXs, inspired by cell-penetrating peptides, as synthetic mimics of HDPs to display potent antifungal activity, superior mammalian cells versus fungi selectivity, and strong therapeutic efficacy in treating local and systemic fungal infections. Moreover, the unique antifungal mechanism of fungal cell membrane penetration and organelle disruption explains the insusceptibility of POXs to antifungal resistance. The easy synthesis and structural diversity of POXs imply their potential as a class of promising antifungal agents.

A multifunctional supramolecular hydrogel for infected wound healing.

Bacterial infection poses a significant threat to wound healing, and the preparation of novel wound dressings is very important. However, currently reported dressings serve as traditional physical barriers or functional ones with limited effects, such as antibacterial effect or adhesion. There is growing demand for developing wound dressing materials with antibacterial effect, good adhesion, proper degradation within the wound recovery time, and simple synthesis. In this study, based on a natural plant extract - tannic acid (TA) and natural guanosine (G), a supramolecular soft hydrogel (G-TA hydrogel) was successfully synthesized based on dynamic borate esters in a one-pot reaction. The hydrogel showed excellent antibacterial and adhesive properties and could be degraded within three days in vivo. In addition, the G-TA hydrogel also showed remarkable antioxidant capability, excellent injectability, a long in vitro lifespan, and good cytocompatibility on L929 cells. Furthermore, the hydrogel could accelerate the healing of full-thickness wounds on the back skin of mice, indicating its promising applications in wound repair.

A sandcastle worm-inspired strategy to functionalize wet hydrogels.

Hydrogels have been extensively used in many fields. Current synthesis of functional hydrogels requires incorporation of functional molecules either before or during gelation via the pre-organized reactive site along the polymer chains within hydrogels, which is tedious for polymer synthesis and not flexible for different types of hydrogels. Inspired by sandcastle worm, we develop a simple one-step strategy to functionalize wet hydrogels using molecules bearing an adhesive dibutylamine-DOPA-lysine-DOPA tripeptide. This tripeptide can be easily modified with various functional groups to initiate diverse types of polymerizations and provide functional polymers with a terminal adhesive tripeptide. Such functional molecules enable direct modification of wet hydrogels to acquire biological functions such as antimicrobial, cell adhesion and wound repair. The strategy has a tunable functionalization degree and a stable attachment of functional molecules, which provides a tool for direct and convenient modification of wet hydrogels to provide them with diverse functions and applications.

Addressing MRSA infection and antibacterial resistance with peptoid polymers.

Methicillin-Resistant Staphylococcus aureus (MRSA) induced infection calls for antibacterial agents that are not prone to antimicrobial resistance. We prepare protease-resistant peptoid polymers with variable C-terminal functional groups using a ring-opening polymerization of N-substituted N-carboxyanhydrides (NNCA), which can provide peptoid polymers easily from the one-pot synthesis. We study the optimal polymer that displays effective activity against MRSA planktonic and persister cells, effective eradication of highly antibiotic-resistant MRSA biofilms, and potent anti-infectious performance in vivo using the wound infection model, the mouse keratitis model, and the mouse peritonitis model. Peptoid polymers show insusceptibility to antimicrobial resistance, which is a prominent merit of these antimicrobial agents. The low cost, convenient synthesis and structure diversity of peptoid polymers, the superior antimicrobial performance and therapeutic potential in treating MRSA infection altogether imply great potential of peptoid polymers as promising antibacterial agents in treating MRSA infection and alleviating antibiotic resistance.

Synthesis of poly-α/ß-peptides with tunable sequence via the copolymerization on N-carboxyanhydride and N-thiocarboxyanhydride.

The fascinating functions of proteins and peptides in biological systems have attracted intense interest to explore their mimics using polymers, including polypeptides synthesized from polymerization. The folding, structures and functions of proteins and polypeptides are largely dependent on their sequence. However, sequence-tunable polymerization for polypeptide synthesis is a long-lasting challenge. The application of polypeptides is also greatly hindered by their susceptibility to enzymatic degradation. Although poly-α/ß-peptide has proven to be an effective strategy to address the stability issue, the synthesis of poly-α/ß-peptide from polymerization is not available yet. Hereby, we demonstrate a living and controlled copolymerization on α-NCA and ß-NTA to prepare sequence-tunable poly-α/ß-peptides. This polymerization strategy shows a prominent solvent-driven characteristic, providing random-like copolymers of poly-α/ß-peptides in THF and block-like copolymers of poly-α/ß-peptides in a mixed solvent of CHCl3/H2O (95/5, v/v), and opens new avenues for sequence-tunable polymerization and enables facile synthesis of proteolysis tunable poly-α/ß-peptides for diverse applications.

Dual mechanism ß-amino acid polymers promoting cell adhesion.

Cell adhesion has tremendous impact on the function of culture platforms and implants. Cell-adhesive proteins and peptides have been extensively used for decades to promote cell adhesion, however, their application suffers from their easy enzymatic degradation, difficulty in large-scale preparation and expensiveness. To develop the next-generation cell-adhesive materials, we mimic the cell adhesion functions and mechanisms of RGD and KRSR peptides and design cell-adhesive cationic-hydrophobic amphiphilic ß-amino acid polymers that are stable upon proteolysis and easily prepared in large scale at low cost. The optimal polymer strongly promotes cell adhesion, using preosteoblast cell as a model, by following dual mechanisms that are independent of sequence and chirality of the statistic copolymer. Our strategy opens avenues in designing the next-generation cell-adhesive materials and may guide future studies and applications.

Peptide-Mimicking Poly(2-oxazoline)s Displaying Potent Antimicrobial Properties.

Poly(2-oxazoline)s have excellent biocompatibility and have been used as FDA-approved indirect food additives. The inert property of the hydrophilic poly(2-oxazoline)s suggests them as promising substitutes for poly(ethylene glycol) (PEG) in various applications such as anti-biofouling agents. It was recently reported that poly(2-oxazoline)s themselves have antimicrobial properties as synthetic mimics of host defense peptides. These studies revealed the bioactive properties of poly(2-oxazoline)s as a new class of functional peptide mimics, by mimicking host defense peptides to display potent and selective antimicrobial activities against methicillin-resistant Staphylococcus aureus both in vitro and in vivo, without concerns about antimicrobial resistance. The high structural diversity, facile synthesis, and potent and tunable antimicrobial properties underscore the great potential of poly(2-oxazoline)s as a class of novel antimicrobial agents in dealing with drug-resistant microbial infections and antimicrobial resistance.

An alpha/beta chimeric peptide molecular brush for eradicating MRSA biofilms and persister cells to mitigate antimicrobial resistance.

Infections involving methicillin-resistant Staphylococcus aureus present great challenges, especially when biofilms and persister cells are involved. In this work, an α/ß chimeric polypeptide molecular brush (α/ß CPMB) is reported to show excellent performance in inhibiting the formation of biofilms and eradicating established biofilms. Additionally, the polymer brush efficiently killed metabolically inactive persister cells that are antibiotic-insensitive. Antimicrobial mechanism studies showed that α/ß CPMB causes membrane disturbance and a substantial increase in reactive oxygen species (ROS) levels to kill bacteria, and mesosome-like structure formation was also observed. Furthermore, the polymer brush was able to kill clinically isolated multidrug resistant Gram-positive bacteria with no risk of antimicrobial resistance. The α/ß CPMB has demonstrated great potential in addressing the great challenge of eradicating multidrug resistant Gram-positive bacterial infections.

Impact of Antifouling PEG Layer on the Performance of Functional Peptides in Regulating Cell Behaviors.

Cell adhesive and other functional peptides (such as RGD, KRSR, YIGSR, VAPG, and BMP-2 peptides) are extensively studied and utilized in tissue engineering scaffolds and biomedical devices to modulate cell functions. Though PEG is frequently used as the antifouling layer, it is unclear how it affects the performance of functional peptides. By analyzing the impact of PEG at short (OEG4), medium (OEG8), and long chain length (PEG2K), we reveal that PEG chain length is critical and a medium-length PEG enables functional peptides to display their optimal and genuine functions in cell adhesion, migration, and differentiation by providing excellent antifouling to minimize background noise of unwanted cell adhesion and high enough surface density of functional peptides. Our result provides new avenues for maximizing the genuine functions of peptides. This study also provides a solution to prevent the heterogeneous and even divergent results caused by inappropriate choice of antifouling PEG and provides a general guidance in identifying new functional peptides.