Modification of polymer surfaces: optimization of approaches

Boron-enriched polyvinyl-alcohol/boric-acid nanoparticles for boron neutron capture therapy

Background: Due to the noninvasive nature of boron neutron capture therapy (BNCT), it is considered a promising cancer treatment method. Aim: To investigate whether polyvinyl alcohol/boric acid crosslinked nanoparticles (PVA/BA NPs) are an efficient delivery system for BNCT. Materials & methods: PVA/BA NPs were synthesized and cocultured with brain and oral cancers cells for BNCT. Results: PVA/BA NPs had a boron-loading capacity of 7.83 ± 1.75 w/w%. They accumulated in brain and oral cancers cells at least threefold more than in fibroblasts and macrophages. The IC50 values of the brain and oral cancers cells were at least ninefold and sixfold lower than those of fibroblasts and macrophages, respectively. Conclusion: Theoretically, PVA/BA NPs target brain and oral cancers cells and could offer improved therapeutic outcomes of BNCT.

International survey on the perioperative management of pulmonary endarterectomy: the perfusion perspective

Introduction:

Pulmonary endarterectomy (PEA) is the most effective treatment available for chronic thromboembolic pulmonary hypertension (CTEPH). Patient selection, surgical technique and perioperative management have improved patient outcomes, which are traditionally linked to surgical and center experience. However, optimal perfusion care has not been well defined. The goal of the international survey was to better characterize the contemporary perfusion management of PEA and highlight similarities and controversies.

Method:

The combined caseload of 15 participating centers was 5,066 cases. Topics queried included materials and types of cardiopulmonary bypass (CPB) equipment, choice of prime, fluid management, deep hypothermia strategy, temperature management, treatment of acid-base abnormalities and intraoperative hematocrit as well as anticoagulation management for heparin-induced thrombocytopenia.

Conclusion:

Our assessment could provide a base for further advancement and may help design future studies to elucidate the impact of perfusion in this challenging field.

Leukocyte filtration and aprotinin: synergistic anti-inflammatory protection

Cardiopulmonary bypass activates an array of cellular and humoral inflammatory mechanisms that culminate in diverse or organ-specific injury. A manifestation of inflammatory injury to the heart, atrial fibrillation ranks among the most frequent and potentially life-threatening postsurgical complications. Pulmonary manifestations of the inflammatory response are also of major concern. Neutrophils activated by passage through the extracorporeal circuit inflict local injury and provoke the inflammatory cascade by producing oxyradicals and proinflammatory factors. This study tested if a combination of leukocyte depletion and aprotinin suppression of neutrophils could minimize postbypass atrial fibrillation and pulmonary dysfunction. In part one, two randomized groups of 90 patients undergoing primary coronary artery bypass grafting received full Hammersmith aprotinin alone (control group) or combined with leukofiltration (study group) and were prospectively examined. The dual treatment decreased the incidence of postoperative atrial fibrillation (7 of 90, 7.8%) by 67% versus aprotinin alone (21 of 90, 23.3%). Respiratory gas exchange in these patients was assessed from pulmonary shunt fraction. In the first two hours postbypass, pulmonary shunt fraction in the dual treatment group increased 40% less than in the group receiving aprotinin alone (p = 0.002), and subsided more quickly and completely over the next six hours. In part two, the cardiopulmonary bypass group receiving aprotinin+leukofiltration was retrospectively compared with 45 patients undergoing off-pump coronary revascularization. A strong, albeit not statistically significant trend (p= 0.08) toward a lower incidence of atrial fibrillation was found in the dual treatment group versus the off-pump group (8 of 45, 17.8%). These findings suggest that combining mechanical and pharmacologic suppression of the systemic inflammatory response could mitigate its deleterious arrhythmic and pulmonary complications.

Clinical significance of coated extracorporeal circuits: a review of novel technologies

Coating of extracorporeal circuits may be a solution to prevent adverse effects induced by the contact of blood elements and proteins with foreign surfaces. This paper reviews the recent novel coating technologies and compares their documented in vitro and ex vivo advantages under the clinical setting. Data presented have also been supported by postclinical biomaterial research to verify biocompatibility and hemocompatibility.

Cell adhesive and antifouling polyvinyl chloride surfaces via wet chemical modification

Polyvinyl chloride (PVC) is one of the most frequently used polymers for the manufacturing of medical devices. Limitations for its usage are based upon unfavorable surface properties of the polymer including its hydrophobicity and lack of functionalities in order to increase its versatility. To address this issue, wet chemical modification of PVC was performed through surface amination using the bifunctional compound ethylene diamine. The reaction was conducted in order to achieve maximum surface amination while leaving the bulk material unaffected. The initial activation step was characterized by means of various methods including contact angle measurements, colorimetric amine quantification, infrared spectroscopy, and gel permeation chromatography. Depth profiles were obtained by a confocal microscopic method using fluorescence labeling. Exclusive surface modification was thus confirmed. To demonstrate biological applications of the presented technique, two examples were chosen: The covalent immobilization of the cell adhesive Asp-Gly-Asp-Ser-peptide (RGD) onto PVC samples yielded a surface that strongly supported cellular adhesion and proliferation of fibroblasts. In contrast, the decoration of PVC with the hydrophilic polymer polyethylene glycol prevented cellular adhesion to a large extent. The impact of these modifications was demonstrated by cell culture experiments.

Advantages of RGD peptides for directing cell association with biomaterials

Despite many years of in vitro research confirming the effectiveness of RGD in promoting cell attachment to a wide variety of biomaterials, animal studies evaluating tissue responses to implanted RGD-functionalized substrates have yielded more variable results. The goals of this report are to present some of the reasons why cell culture studies may not always reliably predict in vivo responses, and more importantly, to highlight potential applications that may benefit from the use of RGD peptides.

Active or passive bio-coating: does it matters in extracorporeal circulation?

Background: Two types of surface coating for cardiopulmonary bypass (CPB) are used: bioactive (heparin, nitric oxide) and biopassive (albumin, polyethyleneoxide (PEO), phosphorylcholine). When haemocompatible coatings are combined with the separation of pleuro-pericardial aspiration, attenuation of both the coagulation and complement cascades, as well as better platelet preservation, has been demonstrated. This study wants to investigate if the combination of a bioactive with a biopassive coating (unfractionated heparin embedded in a phosphorylcholine matrix) combines the beneficial effects of both approaches.

Materials and methods: Thirty patients undergoing elective CABG were prospectively randomized into two groups of 15 patients. The sole exclusion criterion was an ejection fraction of less than 40%. In the control group (PC), the whole CPB circuit was coated with phosphorylcholine (PC). In the study group (XPC), unfractionated heparin was embedded in the PC matrix of the oxygenator and arterial line filter.

Results: No differences were found for haemolytic index, thrombin-anti-thrombin complex (TAT), IL-6, IL-10 and blood loss. PF4 plasma concentration increased from 27.6±22.0 IU/mL to 165.7±43.9 IU/mL (p<0.001) at 15 minutes of CPB in the PC and from 16.0±9.7 IU/mL to 150.9 ± 61.3 IU/mL (p<0.001) in the XPC group. Terminal complement complex (TCC) increased over time in both groups until the end of CPB (Figure 2A). Within each group, TCC generation was statistically significantly higher after the release of the aortic cross-clamp (p<0.001) and at the end of CPB (p<0.001). Total TCC generation was statistically significantly higher in the XPC group compared to the PC group (p=0.026). The difference was statistically significant after the release of the aortic cross-clamp (p=0.005) and at the end of CPB (p=0.001).

Conclusions: Based on our results, there is no additional benefit in combining phosphorylcholine with unfractionated heparin in elective patients undergoing coronary artery bypass grafting (CABG). Massive haemodilution leads to enhanced complement activation.

Search for cyclodextrin-based inhibitors of anthrax toxins: synthesis, structural features, and relative activities

Recently, using structure-inspired drug design, we demonstrated that aminoalkyl derivatives of beta-cyclodextrin inhibited anthrax lethal toxin action by blocking the transmembrane pore formed by the protective antigen (PA) subunit of the toxin. In the present study, we evaluate a series of new beta-cyclodextrin derivatives with the goal of identifying potent inhibitors of anthrax toxins. Newly synthesized hepta-6-thioaminoalkyl and hepta-6-thioguanidinoalkyl derivatives of beta-cyclodextrin with alkyl spacers of various lengths were tested for the ability to inhibit cytotoxicity of lethal toxin in cells as well as to block ion conductance through PA channels reconstituted in planar bilayer lipid membranes. Most of the tested derivatives were protective against anthrax lethal toxin action at low or submicromolar concentrations. They also blocked ion conductance through PA channels at concentrations as low as 0.1 nM. The activities of the derivatives in both cell protection and channel blocking were found to depend on the length and chemical nature of the substituent groups. One of the compounds was also shown to block the edema toxin activity. It is hoped that these results will help to identify a new class of drugs for anthrax treatment, i.e., drugs that block the pathway for toxin translocation into the cytosol, the PA channel.

First preparation of biotinylated gradient polyethylene surface to bind photoactive caged streptavidin

A gradient polyethylene (PE) surface was created through corona treatment, in which the corona power increased along the 5 cm length of the PE. The gradient surface was treated with polyethyleneimine and then biotin. Fluorescein-conjugated streptavidin (SAV) caged within 5-carboxymethoxy-2-nitrobenzyl (CMNB) adsorbed onto the biotinylated gradient PE surface following molecular recognition principles. Photoirradiation decomposed the CMNB cage and allowed the fluorescein-conjugated SAV to fluoresce, the intensity of which increased gradually along the PE surface.

Preparation of a Gradient Biotinylated Polyethylene Surface To Bind Streptavidin−FITC

A novel biotinylated gradient surface was designed to bind a streptavidin-FITC. The gradient polyethylene (PE) surface was prepared by a corona treatment with a power increase along the PE length, and successively, biotinylated gradient PE surface was prepared by the reaction of polyethylenimine (PEI) and biotin. Surface properties of the gradient PE surface changed according to PE length and chemical modification. The biotinylated gradient PE surface provided a continuous gradient of streptavidin-FITC through binding of avidin-biotin. The luminosity of fluorescence that corresponds to a streptavidin-bound FITC on the biotinylated gradient PE surface increased gradually on the surface along the PE length.

Perfusion-assisted beating heart support with a miniature extracorporeal circuit and leukocyte filtration: a 58-year-old patient with severe COPD

Patients with severe chronic obstructive pulmonary disease (COPD) impose a significant risk for postoperative morbidity and mortality requiring cardiovascular surgical intervention and the use of extracorporeal circulation. Recently, we treated a 58-year-old male with acute coronary syndrome complicated with recurrent ventricular arrhythmia, hypoxemia secondary to severe COPD and resolving pneumonia, who required urgent coronary revascularization. A novel operative strategy was used that included beating heart bypass grafting with cardiac decompression and support with a miniature perfusion circuit, kinetic-assisted venous return, rapid autologous priming and leukocyte filtration. The combination of multiple modalities was chosen because the patient was in a pre-existing inflammatory condition and had severe COPD. We herein report our perioperative clinical experience with this patient and the use of multiple modalities for extracorporeal perfusion therapy in managing this challenging case. We believe that, based upon his clinical course of ventilation time (17.4 hours) and postoperative length of hospital stay (5 days), this high risk patient demonstrated a positive clinical outcome as a result of these techniques.