Serum Albumin-Peptide Conjugates for Simultaneous Heparin Binding and Detection

Nano-anticoagulant based on carrier-free low molecular weight heparin and octadecylamine with an albumin shuttling effect

Low-molecular-weight heparin (LMWH), derived from unfractionated heparin (UFH), has enhanced anticoagulant efficacy, long duration of action, and extended half-life. Patients receiving LMWH for preventive therapies would strongly benefit from its long-term effects, however, achieving this is challenging. Here, we design and evaluate a nanoengineered LMWH and octadecylamine conjugate (LMHO) that can act for a long time while maintaining close to 97 ± 3% of LMWH activity via end-specific conjugation of the reducing end of LMWH. LMHO can self-assemble into nanoparticles with an average size of 105 ± 1.7 nm in water without any nanocarrier and can be combined with serum albumin, resulting in a lipid-based albumin shuttling effect. Such molecules can circulate in the bloodstream for 4-5 days. We corroborate the self-assembly capability of LMHO and its interaction with albumin through molecular dynamics (MD) simulations and transmission electron microscopy (TEM) analysis. This innovative approach to carrier-free polysaccharide delivery, enhanced by nanoengineered albumin shuttling, represents a promising platform to address limitations in conventional therapies.

External Trigger Free Charge Switchable Cationic Ligands in the Design of Safe and Effective Universal Heparin Antidote

Thrombosis, the formation of blood clots within a blood vessel, can lead to severe complications including pulmonary embolism, cardiac arrest, and stroke. The most widely administered class of anticoagulants is heparin-based anticoagulants such as unfractionated heparin, low-molecular weight heparins (LMWHs), and fondaparinux. Protamine is the only FDA-approved heparin antidote. Protamine has limited efficacy neutralizing LMWHs and no reversal activity against fondaparinux. The use of protamine can lead to complications, including excessive bleeding, hypotension, and hypersensitivity, and has narrow therapeutic window. In this work, a new concept in the design of a universal heparin antidote: switchable protonation of cationic ligands, is presented. A library of macromolecular polyanion inhibitors (MPIs) is synthesized and screened to identify molecules that can neutralize all heparins with high selectivity and reduced toxicity. MPIs are developed by assembling cationic binding groups possessing switchable protonation states onto a polymer scaffold. By strategically selecting the identity and modulating the density of cationic binding groups on the polymer scaffold, a superior universal heparin reversal agent is developed with improved heparin-binding activity and increased hemocompatibility profiles leading to minimal effect on hemostasis. The activity of this heparin antidote is demonstrated using in vitro and in vivo studies.

Evaluation of the effect of phenylpropanoids on the binding of heparin to human serum albumin and glycosylated human serum albumin concerning anticoagulant activity: A comparison study

The nonenzymatic advanced glycation end products (AGEs) and the accumulation of AGEs are the two main factors associated with the long-term pathogenesis of diabetes. Human serum albumin (HSA) as the most abundant serum protein has a higher fortuity to be modified by nonenzymatic glycation. In this study, the interaction of three phenylpropanoids (caffeic acid (Caf), p-coumaric acid (Cou), and cinnamic acid (Cin)) toward HSA and glycosylated HSA (gHSA) was analyzed by multiple spectroscopic techniques combined with molecular docking. The formation of fibrils in HSA and gHSA was confirmed by the Thioflavin T (ThT) assay. The phenylpropanoids have shown anti-fibrillation properties in vitro. The obtained thermodynamic parameters indicated that hydrogen bonding and van der Waals forces are the main forces in the binding interaction, and the quenching mechanism of the protein fluorescence is static. Molecular docking results, as well as the in vitro results, showed that Caf, Cou, and Cin exhibit more stable interactions with HSA, respectively. In addition, molecular docking analysis showed that Caf and Cou interact well with K199. Given the critical role of K199 in HSA glycosylation in diabetic patients, this process inhibits the interaction of stabilizer compounds and thus accelerates gHSA aggregation.

Revealing the extracellular function of HMGB1 N-terminal region acetylation assisted by a protein semi-synthesis approach

HMGB1 (high-mobility group box 1) is a non-histone chromatin-associated protein that has been widely reported as a representative damage-associated molecular pattern (DAMP) and to play a pivotal role in the proinflammatory process once it is in an extracellular location. Accumulating evidence has shown that HMGB1 undergoes extensive post-translational modifications (PTMs) that actively regulate its conformation, localization, and intermolecular interactions. However, fully characterizing the functional implications of these PTMs has been challenging due to the difficulty in accessing homogeneous HMGB1 with site-specific PTMs of interest. In this study, we developed a streamlined protein semi-synthesis strategy via salicylaldehyde ester-mediated chemical ligations (Ser/Thr ligation and Cys/Pen ligation, STL/CPL). This methodology enabled us to generate a series of N-terminal region acetylated HMGB1 proteins. Further studies revealed that acetylation regulates HMGB1-heparin interaction and modulates HMGB1's stability against thrombin, representing a regulatory switch to control HMGB1's extracellular activity.

Recombinant supercharged polypeptides for safe and efficient heparin neutralization

Heparin is a widely used anticoagulant agent in the clinic. After application, its anticoagulant effect must be reversed to prevent potential side effects. Protamine sulfate (PS) is the only clinically licensed antidote that has been used for this purpose in the last 80 years, which, however, provokes severe adverse effects, such as systemic hypotension and even death. Herein, we demonstrate the potential of supercharged polypeptides as a promising alternative for protamine sulfate. A series of supercharged polypeptides with multiple positive charges was recombinantly produced, and the heparin-neutralizing performance of the polypeptides was evaluated in comparison with PS. It was found that increasing the number of charges significantly enhanced the ability to neutralize heparin and resist the screening effect induced by salt. In particular, the polypeptide bearing 72 charges (K72) exhibited an excellent heparin-neutralizing behavior that was comparable to that of PS. Further in vivo studies revealed that the heparin-triggered bleeding was almost completely alleviated by K72 while a negligible toxic effect was observed. Therefore, such recombinant supercharged polypeptides might replace protamine sulfate as heparin-reversal agents.

A Synthetic Protocell-Based Heparin Scavenger

Heparin is a commonly applied blood anticoagulant agent in clinical use. After treatment, excess heparin needs to be removed to circumvent side effects and recover the blood-clotting cascade. Most existing heparin antidotes rely on direct heparin binding and complexation, yet selective compartmentalization and sequestration of heparin would be beneficial for safety and efficiency. However, such systems have remained elusive. Herein, a semipermeable protein-based microcompartment (proteinosome) is loaded with a highly positively charged chitosan derivative, which can induce electrostatics-driven internalization of anionic guest molecules inside the compartment. Chitosan-loaded proteinosomes are subsequently employed to capture heparin, and an excellent heparin-scavenging performance is demonstrated under physiologically relevant conditions. Both the highly positive scavenger and the polyelectrolyte complex are confined and shielded by the protein compartment in a time-dependent manner. Moreover, selective heparin-scavenging behavior over serum albumin is realized through adjusting the localized scavenger or surrounding salt concentrations at application-relevant circumstances. In vitro studies reveal that the cytotoxicity of the cationic scavenger and the produced polyelectrolyte complex is reduced by protocell shielding. Therefore, the proteinosome-based systems may present a novel polyelectrolyte-scavenging method for biomedical applications.

Engineered Protein Copolymers for Heparin Neutralization and Detection

Heparin is a widely applied anticoagulant agent. However, in clinical practice, it is of vital importance to reverse its anticoagulant effect to restore the blood-clotting cascade and circumvent side effects. Inspired by protein cages that can encapsulate and protect their cargo from surroundings, we utilize three designed protein copolymers to sequester heparin into inert nanoparticles. In our design, a silk-like sequence provides cooperativity between proteins, generating a multivalency effect that enhances the heparin-binding ability. Protein copolymers complex heparin into well-defined nanoparticles with diameters below 200 nm. We also develop a competitive fluorescent switch-on assay for heparin detection, with a detection limit of 0.01 IU mL^-1 in plasma that is significantly below the therapeutic range (0.2-8 IU mL^-1). Moreover, moderate cytocompatibility is demonstrated by in vitro cell studies. Therefore, such engineered protein copolymers present a promising alternative for neutralizing and sensing heparin, but further optimization is required for in vivo applications.

Genetically Engineered Viral Vectors and Organic-Based Non-Viral Nanocarriers for Drug Delivery Applications

Conventional drug delivery systems are challenged by concerns related to systemic toxicity, repetitive doses, drug concentrations fluctuation, and adverse effects. Various drug delivery systems are developed to overcome these limitations. Nanomaterials are employed in a variety of biomedical applications such as therapeutics delivery, cancer therapy, and tissue engineering. Physiochemical nanoparticle assembly techniques involve the application of solvents and potentially harmful chemicals, commonly at high temperatures. Genetically engineered organisms have the potential to be used as promising candidates for greener, efficient, and more adaptable platforms for the synthesis and assembly of nanomaterials. Genetically engineered carriers are precisely designed and constructed in shape and size, enabling precise control over drug attachment sites. The high accuracy of these novel advanced materials, biocompatibility, and stimuli-responsiveness, elucidate their emerging application in controlled drug delivery. The current article represents the research progress in developing various genetically engineered carriers. Organic-based nanoparticles including cellulose, collagen, silk-like polymers, elastin-like protein, silk-elastin-like protein, and inorganic-based nanoparticles are discussed in detail. Afterward, viral-based carriers are classified, and their potential for targeted therapeutics delivery is highlighted. Finally, the challenges and prospects of these delivery systems are concluded.

Application Value of Blood Heparin-Binding Protein in the Diagnosis of Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Objective

To investigate the expression and clinical significance of serum heparin-binding protein (HBP), C-reactive protein (CRP), and white blood cell count (WBC) in an acute exacerbation of chronic obstructive pulmonary disease (COPD).

Methods

A prospective research model was used to select 63 patients with acute exacerbation of chronic obstructive pulmonary disease who were hospitalized in Xuzhou First People's Hospital from January 2020 to June 2020, and among the chronic obstructive pulmonary disease patients who were followed up in our hospital during the same period, 18 patients were in the stable phase, and 43 healthy patients in our hospital during the same period were selected as the healthy control group. 18 patients with stable chronic obstructive pulmonary disease were selected as the observation group, and 43 healthy people who underwent examination at the same time as the control group. For patients with acute COPD recombination, 5 ml of venous blood was collected according to whether the condition of COPD patients with acute exacerbation was stable or not. 5 ml of venous blood was collected for acute exacerbation. According to their clinical symptoms (such as cough, sputum, and asthma), dyspnea score (MRC score), and pulmonary function (FEV1 and FEV1/FVC), it is determined whether the patient's condition is stable. Patients in the stable COPD group will collect 5 ml of venous blood during the outpatient follow-up, and those in the healthy physical examination group will collect veins on the day of the physical examination. In 5 ml of blood, the levels of HBP and CRP in the blood were measured by the enzyme-linked immunosorbent method and the immunoturbidimetric method, respectively, and the peripheral blood WBC was measured by a blood cell analyzer and its supporting reagents. The differences of the three indicators in each group were statistically analyzed. Normally distributed measurement data were compared using t-test, homogeneity of variance of nonnormally distributed measurement data were compared using one-way analysis of variance, uneven variance of nonnormally distributed measurement data were compared using a rank-sum test, and Pearson linear analysis was used for correlation test. Subject working characteristic curve (ROC) was drawn, P < 0.05 means the difference is statistically significant, the receiver working characteristic curve was established, and the area under the curve (AUC) was calculated to analyze blood HBP. The value of blood CRP and peripheral blood WBC counts alone or in combination in the diagnosis of acute exacerbations of chronic obstructive pulmonary disease.

Results

The level of blood heparin-binding protein in the acute exacerbation phase was significantly higher than that in the stable phase and healthy controls (P < 0.05). In the acute exacerbation stage and stable stage group, the blood heparin binding protein, the percentage of leukocytes, neutrophils, and CRP were detected. There is a correlation between (P < 0.05) and a correlation with lung function (FEV1) (P < 0.05). The predictive value of heparin-binding protein, white blood cells, neutrophil percentage, CRP, etc. for the acute exacerbation of chronic obstructive pulmonary disease, with the area under the heparin-binding protein curve, is the largest, and compared with the stable phase, the comparison of heparin-binding protein, white blood cells, and CRP is statistically significant (P < 0.05).

Conclusion

Heparin-binding protein increases in the stable phase and acute exacerbation phase and is related to other inflammatory factors. It is one of the important inflammatory factors in chronic obstructive pulmonary disease. Heparin-binding protein, white blood cells, CRP, etc. have diagnostic and predictive value for acute exacerbation of chronic obstructive pulmonary disease. Heparin-binding protein has the best predictive result, and the combined index test has a better diagnostic predictive value, which is better than single index detection.

Analysis of abnormal intestinal flora on risk of intestinal cancer and effect of heparin on formation of bacterial biofilm

To study the effect of abnormal intestinal flora on the risk of colorectal cancer and the effect of heparin on the formation of bacterial biofilm, 50 patients with colorectal cancer and 50 healthy subjects were selected. The distribution and quantity of bacteria in feces, the levels of D-lactic acid and endotoxin in serum of the two groups were detected. Intestinal flora strains and biofilm growth were also detected in patients with colorectal cancer cultured in different heparin concentrations (0 mg/mL, 5 mg /mL, 10 mg/mL, and 20 mg/mL). The results showed that there was significant difference in the number of major strains of intestinal flora between healthy subjects and colorectal cancer patients before and after operation (P < 0.05). The serum D-lactic acid levels (1.41 ± 0.39, 6.38 ± 1.42 μg/mL) and endotoxin levels (0.62 ± 0.09, 0.80 ± 0.15 EU/mL) in the experimental group were higher than those in the control group (0.91 ± 0.52 μg/mL) (0.05 ± 0.02 EU/mL) before and after operation (P < 0.05). The amount of biofilm formation increased significantly with the increase of heparin concentration (P < 0.05). In summary, there was a close relationship between the occurrence of colorectal cancer and abnormal intestinal flora. Heparin may have a positive effect on regulating intestinal flora in patients with colorectal cancer, which provided certain reference value for the treatment of colorectal cancer.

An indicator displacement assay-based optical chemosensor for heparin with a dual-readout and a reversible molecular logic gate operation based on the pyranine/methyl viologen

We have reported an optical indicator displacement assay (IDA) for heparin with a UV-vis absorbance and fluorescence dual-readout based on pyranine/methyl viologen (MV²⁺). Upon introducing heparin, pyranine/MV²⁺ shows a clearly observable increase in UV-vis absorbance and a turn-on of the fluorescence signal. We have demonstrated that the ionic nature of buffers significantly affects the pyranine displacement and the zwitterionic HEPES was most suitable for heparin sensing. After careful screening of experimental conditions, the pyranine/MV²⁺-based optical chemosensor exhibits a fast, sensitive, and selective response toward heparin. It shows dynamic linear concentration of heparin in the ranges of 0.1-40 U·mL^-1 and 0.01-20 U·mL^-1 for the absorptive and fluorescent measurements, respectively, which both cover the clinically relevant levels of heparin. As with the animal experiments, the optical chemosensor has been demonstrated to be selective and effective for heparin level qualification in rat plasma. The chemosensor is readily accessible, cost-effective, and reliable, which holds a great promise for potential application on clinical and biological studies. Furthermore, this IDA system can serve as an IMPLICATION logic gate with a reversible and switchable logical manner.

Engineered protein cages for selective heparin encapsulation

A heparin-specific binding peptide was conjugated to a cowpea chlorotic mottle virus (CCMV) capsid protein, which was subsequently allowed to encapsulate heparin and form capsid-like protein cages. The encapsulation is specific and the capsid-heparin assemblies display negligible hemolytic activity, indicating proper blood compatibility and promising possibilities for heparin antidote applications.

Heparin stimulates biofilm formation of Escherichia coli strain Nissle 1917

OBJECTIVES

Escherichia coli strain Nissle 1917 (EcN), a gut probiotic competing with pathogenic bacteria, has been used to attenuate various intestinal dysfunctions. Heparin is a sulfated glycosaminoglycan enriched in the human and animal intestinal mucosa, which has a close connection with bacterial biofilm formation. However, the characteristics of heparin affecting bacterial biofilm formation remain obscure. In this study, we investigated the influence of heparin and its derivatives on EcN biofilm formation.

RESULTS

Here, we found that heparin stimulated EcN biofilm formation in a dose-dependent manner. With the addition of native heparin, the EcN biofilm formation increased 6.9- to 10.8-fold than that without heparin, and was 1.4-, 3.1-, 3.0-, and 3.8-fold higher than that of N-desulfated heparin (N-DS), 2-O-desulfated heparin (2-O-DS), 6-O-desulfated heparin (6-O-DS), and N-/2-O-/6-O-desulfated heparin (N-/2-O-/6-O-DS), respectively. Depolymerization of heparin produced chain-shortened heparin fragments with decreased molecular weight. The depolymerized heparins did not stimulate EcN biofilm formation. The OD570 value of EcN biofilm with the addition of chain-shortened heparin fragments was 8.7-fold lower than that of the native heparin. Furthermore, the biofilm formation of Salmonella enterica serovar Typhimurium was also investigated with the addition of heparin derivatives, and the results were consistent with that of EcN biofilm formation.

CONCLUSIONS

We conclude that heparin stimulated EcN biofilm formation. Both the sulfation and chain-length of heparin contributed to the enhancement of EcN biofilm formation. This study increases the understanding of how heparin affects biofilm formation, indicating the potential role of heparin in promoting intestinal colonization of probiotics that antagonize pathogen infections.