PLCL/PCL Dressings with Platelet Lysate and Growth Factors Embedded in Fibrin for Chronic Wound Regeneration

Introduction

The formation of diabetic ulcers (DU) is a common complication for diabetic patients resulting in serious chronic wounds. There is therefore, an urgent need for complex treatment of this problem. This study examines a bioactive wound dressing of a biodegradable electrospun nanofibrous blend of poly(L-lactide-co-ε-caprolactone) and poly(ε-caprolactone) (PLCL/PCL) covered by a thin fibrin layer for sustained delivery of bioactive molecules.

Methods

Electrospun PLCL/PCL nanofibers were coated with fibrin-based coating prepared by a controlled technique and enriched with human platelet lysate (hPL), fibroblast growth factor 2 (FGF), and vascular endothelial growth factor (VEGF). The coating was characterized by scanning electron microscopy and fluorescent microscopy. Protein content and its release rate and the effect on human saphenous vein endothelial cells (HSVEC) were evaluated.

Results

The highest protein amount is achieved by the coating of PLCL/PCL with a fibrin mesh containing 20% v/v hPL (NF20). The fibrin coating serves as an excellent scaffold to accumulate bioactive molecules from hPL such as PDGF-BB, fibronectin (Fn), and α-2 antiplasmin. The NF20 coating shows both fast and a sustained release of the attached bioactive molecules (Fn, VEGF, FGF). The dressing significantly increases the viability of human saphenous vein endothelial cells (HSVECs) cultivated on a collagen-based wound model. The exogenous addition of FGF and VEGF during the coating procedure further increases the HSVECs viability. In addition, the presence of α-2 antiplasmin significantly stabilizes the fibrin mesh and prevents its cleavage by plasmin.

Discussion

The NF20 coating supplemented with FGF and VEGF provides a promising wound dressing for the complex treatment of DU. The incorporation of various bioactive molecules from hPL and growth factors has great potential to support the healing processes by providing appropriate stimuli in the chronic wound.

Complement Activation Dramatically Accelerates Blood Plasma Fouling On Antifouling Poly(2-hydroxyethyl methacrylate) Brush Surfaces

Non-specific protein adsorption (fouling) triggers a number of deleterious events in the application of biomaterials. Antifouling polymer brushes successfully suppress fouling, however for some coatings an extremely high variability of fouling for different donors remains unexplained. The authors report that in the case of poly(2-hydroxyethyl methacrylate) (poly(HEMA)) this variability is due to the complement system activation that causes massive acceleration in the fouling kinetics of blood plasma. Using plasma from various donors, the fouling kinetics on poly(HEMA) is analyzed and correlated with proteins identified in the deposits on the surface and with the biochemical compositions of the plasma. The presence of complement components in fouling deposits and concentrations of C3a in different plasmas indicate that the alternative complement pathway plays a significant role in the fouling on poly(HEMA) through the "tick-over" mechanism of spontaneous C3 activation. The generated C3b binds to the poly(HEMA) surface and amplifies complement activation locally. Heat-inactivated plasma prevents accelerated fouling kinetics, confirming the central role of complement activation. The results highlight the need to take into account the variability between individuals when assessing interactions between biomaterials and blood plasma, as well as the importance of the mechanistic insight that can be gained from protein identification.

Endothelialization of an ePTFE vessel prosthesis modified with an antithrombogenic fibrin/heparin coating enriched with bound growth factors

Early and late thrombosis remain the most frequent reasons for the failure of synthetic cardiovascular grafts. Long-term hemocompatibility of implanted synthetic grafts can be achieved if a natural living endothelium is formed over its blood-contacting surface. Here we present a modification of a standard expanded polytetrafluorethylene (ePTFE) vessel prosthesis by a controlled preparation of a fibrin mesh enriched with covalently bound heparin and noncovalently bound vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). Compared to a bare prosthesis, the coated prosthesis showed excellent antithrombogenic properties after contact with heparinized fresh human blood. Human umbilical vein endothelial cells seeded on the inner surface of the coated prosthesis formed a confluent layer in 5 days, whereas only small colonies of cells were scattered on the bare prosthesis. Viability of the cells was promoted mainly by FGF immobilized on the coating. These findings suggest that the coating may prevent acute thrombus formation and support the self-endothelialization of an implanted ePTFE vascular graft in vivo.

Surface Design of Antifouling Vascular Constructs Bearing Biofunctional Peptides for Tissue Regeneration Applications

Antifouling polymer layers containing extracellular matrix-derived peptide motifs offer promising new options for biomimetic surface engineering. In this contribution, we report the design of antifouling vascular grafts bearing biofunctional peptide motifs for tissue regeneration applications based on hierarchical polymer brushes. Hierarchical diblock poly(methyl ether oligo(ethylene glycol) methacrylate-block-glycidyl methacrylate) brushes bearing azide groups (poly(MeOEGMA-block-GMA-N₃)) were grown by surface-initiated atom transfer radical polymerization (SI-ATRP) and functionalized with biomimetic RGD peptide sequences. Varying the conditions of copper-catalyzed alkyne-azide “click” reaction allowed for the immobilization of RGD peptides in a wide surface concentration range. The synthesized hierarchical polymer brushes bearing peptide motifs were characterized in detail using various surface sensitive physicochemical methods. The hierarchical brushes presenting the RGD sequences provided excellent cell adhesion properties and at the same time remained resistant to fouling from blood plasma. The synthesis of anti-fouling hierarchical brushes bearing 1.2 × 10³ nmol/cm² RGD biomimetic sequences has been adapted for the surface modification of commercially available grafts of woven polyethylene terephthalate (PET) fibers. The fiber mesh was endowed with polymerization initiator groups via aminolysis and acylation reactions optimized for the material. The obtained bioactive antifouling vascular grafts promoted the specific adhesion and growth of endothelial cells, thus providing a potential avenue for endothelialization of artificial conduits.

First experience with diagnosing astroviral infections in children hospitalized in Pilsen (Czechia)

Between the years 2000-2002 astroviral infection was confirmed in 0.8 % of 2606 children admitted for a diarrheal disease to the University Hospital in Pilsen (Czechia). Astrovirus infections most frequently occurred in the age group between 49-60 months, and 77.3 % of the infections occurred in winter. When the incidence was calculated for these most susceptible age groups, the positive rates were 2.4 % (between 49-60 months) and 1.2 % (between 7-12 months) respectively. On average the hospitalization lasted for 5 d, the diarrhea 3.7 d, vomiting 1.1 d, and 40.9 % of infected children had a raised temperature. In 7 out of 872 stool samples (0.8 %), astrovirus antigen has appeared in the course of the monitored period, i.e. nosocomial astrovirus infection was recorded. In view of the rarity of detecting astroviral infections it is probably not effective to include the diagnosis of these infections in the routine panel when examining the children admitted for gastrointestinal infections. The diagnosis of these infections should, however, be performed within the framework of epidemic incidence and in nosocomial infections.

[Diagnosis of rotavirus infections--comparison of various methods]

In 179 samples of faeces from patients hospitalized with diarrhoeal diseases rotavirus infections were examined concurrently by three different sets--the latex agglutination test Diarlex Rota-Adeno (Orion Diagnostica) and two immunoenzyme tests (EIA)--EIA Rotavirus (Test-Line, CR) and IDEIA Rotavirus (Dako Ltd.) By the latex agglutination reaction the rotavirus infection was proved 31 times (17.3%), by the Test-Line test 87 times (48.6%), by the Dako test 96 times (53.6%). During the interval of 0-3 days after the onset of the disease the positivity assessed by different tests was 22.8%, 48.6% and 54.3%, on the 4th-7th day 12.8%, 51.1% and 57.4%, on the 8th and subsequent days 3.7%, 44.4% and 44.4%. Comparison of sets Orion Diagnostica and Dako revealed the sensitivity of the latex agglutination test only as 30.2% and specificity 97.6%. After the 9th day from the onset of the disease the infection was no longer confirmed by the latex agglutination test, while both EIA tests proved the rotavirus antigen up to the 16th day from the onset of the disease.

[Long-term follow-up of nosocomial rotavirus infections at the Infectious Diseases Clinic of the Medical School Hospital in Plzen (1987-1994)]

The authors evaluated in 1987-1994 the incidence of nosocomial rotavirus infections during hospitalization in 1718 junior children, 450 senior children and adults admitted with diarrhoeal diseases. Rotavirus infection was revealed in 6.2 and 1.3% of the patients resp. During hospitalization the rotaviruses were the most frequent causal agent of nosocomial infections. Hospital infection was contracted regardless of the initial diagnosis most frequently by patients aged 0-12 months. The majority of nosocomial rotavirus infections was associated with symptoms of diarrhoeal disease, on average symptomatic infections prolonged the hospitalization period by 4.2 days. The authors discuss the possibility to influence the incidence of these infections.

[Nosocomial rotavirus infections in children]

BACKGROUND

Worldwide rotaviruses cause in young children one third of diarrhoeal diseases which call for hospital admission. Rotaviruses are also considered the most frequent etiological agent of nosocomial diarrhoeal infections. The objective of the present work was an analysis of the etiology of diarrhoea and nosocomial infection, in particular of rotavirus etiology in children under three years of age.

METHODS AND RESULTS

In 1990-1994 a total of 2002 children under three years were admitted to hospital, incl. 1480 (73.9%) on account of diarrhoeal diseases. A rotavirus etiology was proved in 25.4%, adenovirus etiology in 3.3%. As to bacterial infections, salmonellosis was most frequent (24.4%), less frequent campylobacteriosis (8.4%), shigellosis (1.7%), colibacillary infection (1.3%) or yersiniosis (0.2%). In 36.4% cases of gastroenteritis the etiology was not elucidated. Nosocomial infection with rotaviruses was proved in 59 of 1480 patients with diarrhoea (4.0%) and in 4.5% of the total number of 2002 sick children resp. Nesocomial infection developed most frequently between the 4th and 6th day of hospitalization; the clinical picture is not very different, as a rule isoosmolal dehydration which in cca 50% called for parenteral rehydration. About three quarters of the patients have temporarily elevated aminotransferases. As far as the seasonal character of the disease is concerned, the highest incidence was recorded in the following months of the year: I, II, III, IV, X and XI. This two-phase rotaviral incidence of enteritis does, however, not correspond with the incidence of nosocomial infections. Symptomatic treatment is successful. The prognosis is favourable. Nosocomial rotavirus infection protracted hospitalization on average by five days.

CONCLUSIONS

Nosocomial rotavirus gastroenteritis is a serious problem in particular in departments with young children. So far we are unable to influence their occurrence. They are not seasonal, they do not have a different clinical picture or course. Luckily they have a favourable prognosis. However, they prolong the period of hospitalization.

[Long-term follow-up of the etiology of diarrhea with emphasis on the role of rotaviruses in hospitalized patients at the Infectious Disease Clinic of the Medical School Hospital in Plzen]

During 1986-1994 the etiological structure of diarrhoea in hospitalized patients at the Infectious Diseases Clinic, University Hospital Plzen was analyzed. In children under four years most frequently (in 26%) rotaviruses were involved, in older patients their ratio was lower and the decisive pathogenetic organism were salmonellae. In rotavirus infections the shortest hospitalization period was recorded. These infections were encountered all round the year with a maximum prevalence in the winter months.

[Clinical and epidemiologic findings in studies of Campylobacter infections]

During the period between May 1987 and April 1989 from 929 patients hospitalized at the Clinic for Infectious Diseases with acute diarrhoeal disease Campylobacter infection was detected in 10.6%; a bacterial aetiology was confirmed in 29%. The maximum incidence of campylobaterioses was in the summer months, among those affected children aged 1-14 years predominated. Analysis of the course of the disease in children under three years revealed typical high fever and blood in the faeces--in half the patients. Carriership of Campylobaters was short, as a rule 2-3 weeks. In cases reported to the hygiene service in the region contact with animals was reported by half the patients. In particular chickens and smoked meat products were considered a suspect vehicle.

[Clinical and epidemiologic findings from a study of rotavirus infections in hospitalized children]

The authors examined in 1986-1988 the aetiology of acute diarrhoea in 323 children hospitalized at the Infectious Diseases Clinic in Plzen. An infectious aetiology was proved in 47.7% of the children, the most frequently detected aetiological agent were rotaviruses which caused 28% of the recorded diseases. Their prevalence culminated in December--May; as to age, children between 7 and 24 months predominated. In 41.1% of the subjects with rotavirus infection respiratory symptoms were present all round the year, in 65.5% children transiently pathological transaminase values were recorded. Of 145 children where by laboratory methods nosocomial intestinal infections were monitored, this infection was contracted by 14 children (9.6%). The most frequent causal agent of these diseases were rotaviruses.