Electromechanical properties of dried tendon and isoelectrically focused collagen hydrogels

Assembling artificial collagenous tissues with structural, functional, and mechanical properties which mimic natural tissues is of vital importance for many tissue engineering applications. While the electro-mechanical properties of collagen are thought to play a role in, for example, bone formation and remodeling, this functional property has not been adequately addressed in engineered tissues. Here the electro-mechanical properties of rat tail tendon are compared with those of dried isoelectrically focused collagen hydrogels using piezoresponse force microscopy under ambient conditions. In both the natural tissue and the engineered hydrogel D-periodic type I collagen fibrils are observed, which exhibit shear piezoelectricity. While both tissues also exhibit fibrils with parallel orientations, Fourier transform analysis has revealed that the degree of parallel alignment of the fibrils in the tendon is three times that of the dried hydrogel. The results obtained demonstrate that isoelectrically focused collagen has similar structural and electro-mechanical properties to that of tendon, which is relevant for tissue engineering applications.

Preferential cell response to anisotropic electro-spun fibrous scaffolds under tension-free conditions

Anisotropic alignment of collagen fibres in musculoskeletal tissues is responsible for the resistance to mechanical loading, whilst in cornea is responsible for transparency. Herein, we evaluated the response of tenocytes, osteoblasts and corneal fibroblasts to the topographies created through electro-spinning and solvent casting. We also evaluated the influence of topography on mechanical properties. At day 14, human osteoblasts seeded on aligned orientated electro-spun mats exhibited the lowest metabolic activity (P < 0.001). At day 5 and at day 7, no significant difference was observed in metabolic activity of human corneal fibroblasts and bovine tenocytes respectively seeded on different scaffold conformations (P > 0.05). Osteoblasts and corneal fibroblasts aligned parallel to the direction of the aligned orientated electro-spun mats, whilst tenocytes aligned perpendicular to the aligned orientated electro-spun mats. Mechanical evaluation demonstrated that aligned orientated electro-spun fibres exhibited significant higher stress at break values than their random aligned counterparts (P < 0.006) and random orientated electro-spun fibres exhibited significant higher strain at break values than the aligned orientated scaffolds (P < 0.006). While maintaining fibre structure, we also developed a co-deposition method of spraying and electro-spinning, which enables the incorporation of microspheres within the three-dimensional structure of the scaffold.

Pharmacological activity of ibuprofen released from mesoporous silica

Novel drug delivery systems (DDS) to improve the pharmacokinetic profile of hydrophobic drugs following oral administration are an area of keen interest in drug research. An ideal DDS should not adversely affect drug activity, be capable of delivering a therapeutic dose of drug, and allow homogenous drug loading and drug release. Mesoporous silica has been proposed for this application, with ibuprofen employed as the model drug. It was hypothesised that mesoporous silica MCM-41 is capable of delivering a pharmacologically therapeutic dose of ibuprofen. Ibuprofen-loaded MCM-41 can be prepared reproducibly at a drug to carrier ratio of 30% (wt/wt). The release profile was seen to be 90% within 2 h. Initial assessment of COX-1 inhibitory activity suggests the absence of adverse effects attributable to drug-carrier interaction. The results of this study provide further evidence in support of the proposed use of mesoporous silica in drug delivery.

A biomaterials approach to peripheral nerve regeneration: bridging the peripheral nerve gap and enhancing functional recovery

Microsurgical techniques for the treatment of large peripheral nerve injuries (such as the gold standard autograft) and its main clinically approved alternative--hollow nerve guidance conduits (NGCs)--have a number of limitations that need to be addressed. NGCs, in particular, are limited to treating a relatively short nerve gap (4 cm in length) and are often associated with poor functional recovery. Recent advances in biomaterials and tissue engineering approaches are seeking to overcome the limitations associated with these treatment methods. This review critically discusses the advances in biomaterial-based NGCs, their limitations and where future improvements may be required. Recent developments include the incorporation of topographical guidance features and/or intraluminal structures, which attempt to guide Schwann cell (SC) migration and axonal regrowth towards their distal targets. The use of such strategies requires consideration of the size and distribution of these topographical features, as well as a suitable surface for cell-material interactions. Likewise, cellular and molecular-based therapies are being considered for the creation of a more conductive nerve microenvironment. For example, hurdles associated with the short half-lives and low stability of molecular therapies are being surmounted through the use of controlled delivery systems. Similarly, cells (SCs, stem cells and genetically modified cells) are being delivered with biomaterial matrices in attempts to control their dispersion and to facilitate their incorporation within the host regeneration process. Despite recent advances in peripheral nerve repair, there are a number of key factors that need to be considered in order for these new technologies to reach the clinic.

Regeneration and repair of tendon and ligament tissue using collagen fibre biomaterials

Collagen fibres are ubiquitous macromolecular assemblies in nature, providing the structures that support tensile mechanical loads within the human body. Aligned type I collagen fibres are the primary structural motif for tendon and ligament, and therefore biomaterials based on these structures are considered promising candidates for mediating regeneration of these tissues. However, despite considerable investigation, there remains no collagen-fibre-based biomaterial that has undergone clinical evaluation for this application. Recent research in this area has significantly enhanced our understanding of these complex and challenging biomaterials, and is reinvigorating interest in the development of such structures to recapitulate mechanical function. In this review we describe the progress to date towards a ligament or tendon regeneration template based on collagen fibre scaffolds. We highlight reports of particular relevance to the development of the underlying biomaterials science in this area. In addition, the potential for tailoring and manipulating the interactions between collagen fibres and biological systems, as hybrid biomaterial-biological ensembles, is discussed in the context of developing novel tissue engineering strategies for tendon and ligament.

Chronic closed transection of the biceps brachii: a case report

A 32-year-old man presented with chronic closed transection of the biceps brachii of the right arm after 30 months of conservative treatment. Magnetic resonance imaging showed atrophy of both long and short heads of the biceps brachii, with a 5-cm defect secondary to proximal and distal retraction on either side of the tear. There was a similar defect in the coracobrachialis, but the triceps brachii was normal. The self-rated overall arm status was 4 out of 10 (using a visual analogue scale). Objective functional deficit was measured using a dynamometer. Forearm flexion and supination strength of each arm at 120º/s was tested. The patient had a 34% deficit (40 vs. 61 Nm) in peak torque during forearm flexion and a 22% deficit (10 vs. 12 Nm) during forearm supination. The patient could not maintain maximal torque throughout the range of motion, with an approximately 50% deficit in the later part of the range of motion. The patient underwent reconstruction of the biceps brachii using an interposition Achilles tendon allograft.

End functionalized polymeric system derived from pyrrolidine provide high transfection efficiency

Chemical architecture and functionality play an important role in the physico-chemical properties of cationic polymers with applications as gene vectors. In this study, linear homopolymers of N-ethyl pyrrolidine methacrylamide (EPA), copolymers of EPA with N,N-dimethylacrylamide (DMA) and oligomers of EPA were synthesized, and the resulting structures were evaluated for their transfection efficiency as non-viral gene vectors. Specifically, polymer species with high and low molecular weights (120-2.6 kDa) and different functionalities (tertiary amines as side chains and primary amine as chain end) were prepared as non-crosslinked, linear homopolymers, copolymers and oligomers, respectively. Polymer/DNA complexes (polyplexes) formation was evaluated by agarose gel electrophoresis, showing that all systems complexed with DNA in all P/N ratios with the exception of the EPA homopolymer. Furthermore, light scattering measurements and transmission electronic microscopy (TEM) showed different size (50-450 nm) and morphology depending on the composition and concentration of the polyplex systems. Cell viability and proliferation after contact with polymer and polyplexes were studied using 3T3 fibroblasts, and the systems showed an excellent biocompatibility at 2 and 4 days. Transfection studies were performed with plasmid Gaussian luciferase kit and were found that the highest transfection efficiency in serum free was obtained with oligomers from the P/N ratio of 1/6 to 1/10. Transfection values of the functionalized oligomers with respect to the control linear poly (dimethylaminoethyl methacrylate) [poly (DMAEMA)] are very interesting in the presence of serum. Haemolysis for these polymers values below 1%, which provide attractive potential applications in gene therapy with these non-toxic readsorbable polymers.

A reliable method for detecting complexed DNA in vitro

Quantification of eluted nucleic acids is a critical parameter in characterizing biomaterial based gene-delivery systems. The most commonly used method is to assay samples with an intercalating fluorescent dye such as PicoGreen®. However, this technique was developed for unbound DNA and the current trend in gene delivery is to condense DNA with transfection reagents, which interfere with intercalation. Here, for the first time, the DNA was permanently labeled with the fluorescent dye Cy5 prior to complexation, an alternative technique hypothesized to allow quantification of both bound and unbound DNA. A comparison of the two methods was performed by quantifying the elution of six different varieties of DNA complexes from a model biomaterial (collagen) scaffold. After seven days of elution, the PicoGreen® assay only allowed detection of three types of complexes (those formed using Lipofectin™ and two synthesised copolymers). However, the Cy5 fluorescent labeling technique enabled detection of all six varieties including those formed via common transfection agents poly(ethylene imine), poly-L-lysine and SuperFect™. This allowed reliable quantification of the elution of all these complexes from the collagen scaffold. Thus, while intercalating dyes may be effective and reliable for detecting double-stranded, unbound DNA, the technique described in this work allowed reliable quantification of DNA independent of complexation state.

Routine antibiotic use in preterm neonates: a randomised controlled trial

The immature immune system of preterm neonates puts them at higher risk of neonatal sepsis. We conducted a part-blinded randomised controlled trial to compare the effect of routine antibiotic treatment on the incidence of clinical sepsis in preterm neonates. Preterm neonates without other risk factors for infection admitted in the first 12h of life were randomised to receive routine antibiotics or to a control group (no antibiotics unless clinically indicated). The primary outcome variable was the incidence of clinical sepsis. Secondary outcomes were the incidence of positive blood cultures, necrotising enterocolitis (NEC) stage II or III, or death, and the duration of hospital stay. The incidence of clinical sepsis was comparable in both groups (intervention 31.9%, control 25.4%; P=0.392). Mortality was equivalent in both groups. The control group had significantly more positive blood cultures (P=0.002). The incidence of NEC and the duration of hospital stay were comparable in both groups. In low risk preterm neonates we found no evidence that routine antibiotic use has a protective effect.

Perspective on biomaterials used in the surgical treatment of morbid obesity

Morbid obesity is defined as having a body mass index greater than or equal to 40.0 kg m(-2), or 37.0 kg m(-2) with comorbidities. Bariatric surgery remains the most effective treatment for morbid obesity. Bariatric procedures such as sleeve gastrectomy, vertical banded gastroplasty and adjustable gastric banding all generate excess body-weight loss typically over 3-5 years. The biomaterials used during these procedures, namely silicone, polypropylene, expanded polytetrafluoroethylene and titanium, are all non-degradable biomaterials. Hence, their presence in vivo exceeds the functional requirement of an implant to treat morbid obesity. Accordingly, research into non-invasive and reversible surgical procedures has increased, particularly in light of the dramatic increase in paediatric obesity. Tissue engineering is an alternative approach to treat morbid obesity, as it incorporates both engineering and biological principles into the design and development of an implant to surgically treat morbid obesity. It is hypothesized that a biodegradable polymer to treat morbid obesity could be developed to effectively promote excess weight loss. The aim of this review is to discuss morbid obesity with regards to its aetiology, prevalence and current modalities of treatment. Specifically, the shortcomings of the biomaterials currently used to surgically treat morbid obesity shall be reviewed, and alternative biomaterials shall be proposed.

Developing research competencies through a project-based tissue-engineering module in the biomedical engineering undergraduate curriculum

In addressing the task of developing an undergraduate module in the field of tissue engineering, the greatest challenge lies in managing to capture what is a growing and rapidly changing field. Acknowledging the call for the development of greater critical thinking and interpersonal skills among the next generation of engineers as well as encouraging students to engage actively with the dynamic nature of research in the field, the module was developed to include both project-based and cooperative-learning experiences. These learning activities include developing hypotheses for the application of newly introduced laboratory procedures, a collaborative mock grant submission, and debates on ethical issues in which students are assigned roles as various stakeholders. Feedback from module evaluations has indicated that, while students find the expectations challenging, they are able to gain an advanced insight into a dynamic field. More importantly, students develop research competencies by engaging in activities that require them to link current research directions with their own development of hypotheses for future tissue-engineering applications.

Assessment of wound healing in the alloxan-induced diabetic rabbit ear model

The enhancement of diabetic wound healing represents a major clinical challenge to researchers. The challenge faced is to identify a suitable animal model that best represents the human situation. However, the majority of diabetic wound healing models are in rodents and are hindered by rapid contraction and thus do not reflect epithelial cell migration, as seen in the human wound. The alloxan-induced diabetic rabbit model is a cheap, reproducible model and offers the advantage of providing a noncontractile avascular wound bed. This study aimed to compare the effects of acute hyperglycemia in the alloxan model to normal rabbit controls on wound healing, using methods of stereology. Alloxan was administered 7 days prior to surgery. Four full-thickness punch biopsy wounds were created on each ear (n = 4). Wounds were excised at 7 and 14 days and prepared for stereological analysis from Masson's trichrome-stained histological sections. It was noted that the alloxan-treated animals showed an increase in the number of inflammatory cells and fibroblasts at 14 days. In addition, it was noted that the length density of blood vessels was reduced in the alloxan-induced diabetic rabbits, representing a greater radial diffusion distance between vessels and a less efficient network for nutrient exchange. This is the first study to take a stereological approach to defining the effects of diabetes mellitus on wound healing in a noncontractile model.

Use of tissue transglutaminase and fibronectin to influence osteoblast responses to tricalcium phosphate scaffolds

To explore the possibility of controlling cell interaction with biomaterials, tricalcium phosphate scaffolds were modified using the enzyme tissue transglutaminase (tTgase) in conjunction with fibronectin. Previous reports in the literature have highlighted a number of favourable responses that this protein-enzyme complex can stimulate, including enhancing both cell adhesion, and mineralisation. Fibronectin and tTgase alone were used as controls, and a series of different concentrations of tTgase and fibronectin in combination were assessed. Cell metabolic activity, alkaline phosphatase production, and collagen content were all measured in cultures up to 28 days. Using tetracycline labelling, calcium containing multilayered regions were imaged and quantified. Addition of 6 microg fibronectin resulted in increased alkaline phosphatase activity in all combinations, while increased transglutaminase resulted in more collagen in the cell lysates. Samples treated with fibronectin produced many small mineralised areas, those with 6 microg fibronectin and transglutaminase produced numerous large mineralised areas. The mixture of fibronectin and transglutaminase may prove to be a useful treatment for producing increased osteoblast differentiation on scaffolds.

HIV-1 drug resistance genotyping quality assessment: results of the ENVA7 Genotyping Proficiency Programme

BACKGROUND

Drug-resistance testing plays a critical role in selection of optimal treatment regimens for HIV infected individuals. Laboratories performing testing must implement quality control measures including external quality assessment.

OBJECTIVES

The ENVA7 Programme (2007) was organised by QCMD to assess the performance of laboratories testing for drug-resistance mutations in the HIV-1 Protease and Reverse Transcriptase genes.

STUDY DESIGN

The ENVA7 panel consisted of 5 lyophilised plasma samples (HIV-1 subtypes B, C and F). The viruses harboured wild type or resistant genotypes at various positions of the PR and RT genes. All IAS-defined resistance-associated codons were scored in comparison to the consensus sequence for each sample using a scoring system developed to allow simple and standardised comparisons between laboratories and/or technologies.

RESULTS

111 laboratories from 44 countries participated of which 95 submitted 98 datasets. 36 datasets were generated using ViroSeq (Abbott), 27 using TruGene (Siemens) and 35 using in-house assays.

CONCLUSIONS

All technologies successfully genotyped each of the panel samples, irrespective of the virus subtype. While the assays for genotypic HIV drug-resistance determination have evolved into reliable and technically capable procedures of generating high quality results, variation in the quality of results is still observed between laboratories.

Assessment of cell viability in a three-dimensional enzymatically cross-linked collagen scaffold

Microbial transglutaminase (mTGase) is an enzyme that introduces a covalent bond between peptide bound glutamine and lysine residues. Proteins cross-linked in this manner are often more resistant to proteolytic degradation and show increased tensile strength. This study evaluates the effects of mTGase mediated cross-linking of collagen on the cellular morphology, behaviour and viability of murine 3T3 fibroblasts following their seeding into collagen scaffolds. Additionally, cell mediated scaffold contraction, porosity and level of cross-linking of the scaffold has been analysed using image analysis software, scanning electron microscopy (SEM), colorimetric assays, and Fourier transform infrared spectroscopy (FTIR). We demonstrate that the biocompatibility and cellular morphology, when comparing cultures of fibroblasts integrated in mTGase cross-linked collagen scaffolds with the native collagen counterparts, remained unaffected. It has been also elicited that the structural characteristics of collagen have been preserved while introducing enzymatically resistant covalent bonds.

Endothelial cell response to biomechanical forces under simulated vascular loading conditions

In vivo, endothelial cells (EC) are constantly exposed to the haemodynamic forces (HF) of pressure, wall shear stress and hoop stress. The main aim of this study was to design, create and validate a novel perfusion bioreactor capable of delivering shear stress and intravascular pressure to EC in vitro and to characterise their morphology, orientation and gene expression. Here we report the creation and validation of such a simulator and the dual application of pressure (120/60 mmHg) and low shear stress (5 dyn/cm(2)) to a monolayer of EC established on a non-compliant silicone tube. Under these conditions, EC elongated and realigned obliquely to the direction of applied shear stress in a time-dependent manner. Furthermore, randomly distributed F-actin microfilaments reorganised into long, dense stress fibres crossing the cells in a direction perpendicular to that of flow. Finally, combinatorial biomechanical conditioning of EC induced the expression of the inflammatory-associated E-selectin gene.

Safety and reactogenicity of a low dose diphtheria tetanus acellular pertussis vaccine (Boostrix) in pre-school Indian children

OBJECTIVE

To evaluate the safety and reactogenicity of a reduced-antigen-content combined Diphtheria Tetanus Acellular Pertussis (dTpa) vaccine in Indian preschool children.

METHODS

GlaxoSmithKline Biologicals combination dTpa vaccine was administered as a single booster dose to 347 children aged 46 years in seven centers across India. All children were subsequently followed up for two weeks for safety and reactogenicity assessment.

RESULTS

A total of 345 subjects completed the study and two subjects were lost to follow-up. One serious adverse event (head injury) unrelated to vaccination was reported. Otherwise, all subjects were in good health throughout the study period. Three subjects (0.9%) reported transient general symptoms (such as irritability and drowsiness), which prevented normal activity. Pain at injection site, swelling and redness was reported in 31.1%, 18.2% and 8.9% subjects respectively. Five subjects (1.4%) reported severe pain preventing normal movement. This resolved within 48 hours in all cases. There were no other severe local reactions including large injection site reactions.

CONCLUSION

The reduced antigen content combined dTpa vaccine is safe and well tolerated in Indian pre-school children.

Exacerbations of asthma and chronic obstructive pulmonary disease (COPD): focus on virus induced exacerbations

Asthma and chronic obstructive pulmonary disease (COPD) are the 2 most prevalent chronic airway diseases. Much of the morbidity, mortality and health care costs of the diseases are associated with acute exacerbations, which are episodes of increased symptoms and airflow obstruction. Over the last decade evidence has emerged implicating virus respiratory tract infections as a major cause of exacerbations of both asthma and COPD. Current therapies are not very effective in the prevention or treatment of virus-induced exacerbations and exacerbations are therefore a major unmet medical need. The development of new and novel treatments requires a better understanding of the molecular and cellular mechanisms linking virus infection with exacerbations of asthma and COPD. This article provides an overview of current knowledge regarding the mechanisms of virus-induced exacerbations in both asthma and COPD. It will also review existing treatments and future treatments that are in advanced stages of development.

Maternal blood aspiration: an unusual cause of respiratory distress in a neonate

Maternal blood aspiration is an unusual cause of respiratory distress in neonates. It is occasionally seen in babies born to mothers with antepartum haemorrhage (APH). We report a term neonate with a history of maternal APH who developed respiratory distress soon after birth with a radiological appearance compatible with aspiration syndrome. The infant required ventilation for 36 hours. The aspirated blood was the mother's.

Silicon gel sheeting for preventing and treating hypertrophic and keloid scars

BACKGROUND

Keloid and hypertrophic scars are common and are caused by a proliferation of dermal tissue following skin injury. They cause functional and psychological problems for patients, and their management can be difficult. The use of silicon gel sheeting to prevent and treat hypertrophic scarring is still relatively new, and started in 1981 with treatment of burn scars.

OBJECTIVES

To determine the effectiveness of silicon gel sheeting for: (1) prevention of hypertrophic or keloid scarring in people with newly healed wounds (e.g. post surgery); (2) treatment of established scarring in people with existing keloid or hypertrophic scars.

SEARCH STRATEGY

Trials were identified from searches of the Cochrane Wounds Group Specialised Register (searched September 2005), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 3, 2005); MEDLINE (1989 to June 2002); EMBASE (1988 to May 2002); CINAHL (1982 to May 2002) and reference lists of articles and relevant reviews. The major supplier of silicon gel sheeting (Smith and Nephew) was approached for details of unpublished, ongoing and recently published trials.

SELECTION CRITERIA

Any randomised or quasi-randomised controlled trials, or controlled clinical trials comparing silicon gel sheeting for prevention or treatment of hypertrophic or keloid scars against no treatment, placebo, or any other treatment type except surgery.

DATA COLLECTION AND ANALYSIS

All relevant trials were assessed for methodological quality. Data were extracted independently by both reviewers using a standardized form, and the results cross-checked. All trials, meeting the selection criteria were assessed for methodological quality.

MAIN RESULTS

Thirteen trials, involving 559 people, ranging in age from 2 to 81 years, were included in the review. The trials compared adhesive silicon gel sheeting with control; non-silicon gel sheeting; silicon gel plates with added Vitamin E; laser therapy; triamcinolone acetonide injection, and non-adhesive silicon gel sheeting. In the prevention studies, when compared with a no treatment option; whilst silicon gel sheeting reduced the incidence of hypertrophic scarring in people prone to scarring, (RR 0.46, 95% CI 0.21 to 0.98) these studies were highly susceptible to bias. Silicon gel sheeting produced a statistically significant improvement in scar elasticity, (RR 8.60, 95% CI 2.55 to 29.02), but again these studies were highly susceptible to bias.

AUTHORS' CONCLUSIONS

Trials evaluating silicon gel sheeting as a treatment for hypertrophic and keloid scarring are of poor quality and highly susceptible to bias. There is weak evidence of a benefit of silicon gel sheeting as a prevention for abnormal scarring in high risk individuals but the poor quality of research means a great deal of uncertainty prevails.

Gastric aspirate shake test for diagnosis of surfactant deficiency in neonates with respiratory distress

The gastric aspirate shake test (GST) was evaluated in 77 newborns with respiratory distress for predicting hyaline membrane disease (HMD) at KEM Hospital, Pune, India.

METHODS

Over 0.5 ml of gastric fluid was obtained within 30 min of birth and mixed with an equal volume of normal saline for 10 sec; 1 ml of 95% ethanol was then added and the mixture agitated for 10 sec. After standing for 15 min, the air-liquid interface was examined for bubbles.

RESULTS

All 21 infants with a negative GST developed HMD. However, 12 infants with an intermediate and nine with a positive test also developed HMD. None of the infants with other respiratory disorders, e.g. transient tachypnoea and pneumonia, had a negative GST. A negative GST had a specificity of 100%, sensitivity of 70% and positive predictive value of 100% for developing HMD.

CONCLUSION

GST is a useful test for predicting HMD and might be of particular value in developing countries.