Reactive Amine Functionalized Microelectrode Arrays Provide Short-Term Benefit but Long-Term Detriment to In Vivo Recording Performance

Intracortical microelectrode arrays (MEAs) are used for recording neural signals. However, indwelling devices result in chronic neuroinflammation, which leads to decreased recording performance through degradation of the device and surrounding tissue. Coating the MEAs with bioactive molecules is being explored to mitigate neuroinflammation. Such approaches often require an intermediate functionalization step such as (3-aminopropyl)triethoxysilane (APTES), which serves as a linker. However, the standalone effect of this intermediate step has not been previously characterized. Here, we investigated the effect of coating MEAs with APTES by comparing APTES-coated to uncoated controls in vivo and ex vivo. First, we measured water contact angles between silicon uncoated and APTES-coated substrates to verify the hydrophilic characteristics of the APTES coating. Next, we implanted MEAs in the motor cortex (M1) of Sprague-Dawley rats with uncoated or APTES-coated devices. We assessed changes in the electrochemical impedance and neural recording performance over a chronic implantation period of 16 weeks. Additionally, histology and bulk gene expression were analyzed to understand further the reactive tissue changes arising from the coating. Results showed that APTES increased the hydrophilicity of the devices and decreased electrochemical impedance at 1 kHz. APTES coatings proved detrimental to the recording performance, as shown by a constant decay up to 16 weeks postimplantation. Bulk gene analysis showed differential changes in gene expression between groups that were inconclusive with regard to the long-term effect on neuronal tissue. Together, these results suggest that APTES coatings are ultimately detrimental to chronic neural recordings. Furthermore, interpretations of studies using APTES as a functionalization step should consider the potential consequences if the final functionalization step is incomplete.

What is the evidence for the use of biologic or biosynthetic meshes in abdominal wall reconstruction?

INTRODUCTION

Although many surgeons have adopted the use of biologic and biosynthetic meshes in complex abdominal wall hernia repair, others have questioned the use of these products. Criticism is addressed in several review articles on the poor standard of studies reporting on the use of biologic meshes for different abdominal wall repairs. The aim of this consensus review is to conduct an evidence-based analysis of the efficacy of biologic and biosynthetic meshes in predefined clinical situations.

METHODS

A European working group, "BioMesh Study Group", composed of invited surgeons with a special interest in surgical meshes, formulated key questions, and forwarded them for processing in subgroups. In January 2016, a workshop was held in Berlin where the findings were presented, discussed, and voted on for consensus. Findings were set out in writing by the subgroups followed by consensus being reached. For the review, 114 studies and background analyses were used.

RESULTS

The cumulative data regarding biologic mesh under contaminated conditions do not support the claim that it is better than synthetic mesh. Biologic mesh use should be avoided when bridging is needed. In inguinal hernia repair biologic and biosynthetic meshes do not have a clear advantage over the synthetic meshes. For prevention of incisional or parastomal hernias, there is no evidence to support the use of biologic/biosynthetic meshes. In complex abdominal wall hernia repairs (incarcerated hernia, parastomal hernia, infected mesh, open abdomen, enterocutaneous fistula, and component separation technique), biologic and biosynthetic meshes do not provide a superior alternative to synthetic meshes.

CONCLUSION

The routine use of biologic and biosynthetic meshes cannot be recommended.

Systematic review of guidelines for the assessment and management of high-grade anal intraepithelial neoplasia (AIN II/III)

AIM

There is ambiguity with regard to the optimal management of anal intraepithelial neoplasia (AIN) III. The aim of this review was to assess and compare international/national society guidelines currently available in the literature on the management, treatment and surveillance of AIN III. We also aimed to assess the quality of the studies used to compile the guidelines and to clarify the terminology used in histological assessment.

METHOD

An electronic search of PubMed and Embase was performed using the search terms 'anal intraepithelial neoplasia', 'AIN', 'anal cancer', 'guidelines', 'surveillance' and 'management'. Literature reviews and guidelines or practice guidelines in peer reviewed journals from 1 January 2000 to 31 December 2014 assessing the treatment, surveillance or management of patients with AIN related to human papilloma virus were included. The guidelines identified by the search were assessed for the quality of evidence behind them using the Oxford Centre for Evidence-based Medicine 2011 Levels of Evidence.

RESULTS

The database search identified 5159 articles and two further guidelines were sourced from official body guidelines. After inclusion criteria were applied, 28 full-text papers were reviewed. Twenty-five of these were excluded, leaving three guidelines for inclusion in the systematic review: those published by the Association of Coloproctology of Great Britain and Ireland, the American Society of Colon and Rectal Surgeons and the Italian Society of Colorectal Surgery. No guidelines were identified on the management of AIN III from human papilloma virus associations and societies. All three guidelines agree that a high index of clinical suspicion is essential for diagnosing AIN with a disease-specific history, physical examination, digital rectal examination and anal cytology. There is interchange of terminology from high-grade AIN (HGAIN) (which incorporates AIN II/III) and AIN III in the literature leading to confusion in therapy use. Treatment varies from immunomodulation and photodynamic therapy to targeted destruction of areas of HGAIN/AIN II/III using infrared coagulation, electrocautery, cryotherapy or surgical excision but with little consensus between the guidelines. Recommendations on surveillance strategies are similarly discordant, ranging from 6-monthly physical examination to annual anoscopy ± biopsy. Over 50% of the recommendations are based on Level 3 or Level 4 evidence and many were compiled using studies that were more than 10 years old.

CONCLUSION

Despite concordance regarding diagnosis, there is significant variation in the guidelines over recommendations on the treatment and surveillance of patients with HGAIN/AIN II/III. All three sets of guidelines are based on low level, outdated evidence originating from the 1980s and 1990s.

Delayed absorbable synthetic plug (GORE® BIO-A®) for the treatment of fistula-in-ano: a systematic review

AIM

Recent advances in the treatment of fistula-in-ano have focused on surgical techniques that preserve sphincter integrity. Plugs that obliterate the lumen of the fistula track have been proposed as one such method, and may be derived from biological or delayed absorbable synthetic materials. Biological plugs have highly variable results and have not been widely adopted. The aim of this systematic review was to assess the effectiveness and safety of a delayed absorbable synthetic plug (GORE® BIO-A®) for treatment of anal fistula.

METHOD

A systematic review of all literature in the English language relevant to the use of a plug to treat anal fistula and published between 1 January 2008 and 15 February 2015 was carried out by searching MEDLINE, EMBASE and the Cochrane Library of Systematic Reviews/Controlled Trials for relevant literature. Relevant articles were identified, quality assessed using the methodological index for nonrandomized studies criteria and data were extracted by two independent researchers (SKN and NNA). The identified articles were assessed with regard to fistula healing rate, duration of follow-up and complication rates related to the use of delayed absorbable synthetic fistula plugs.

RESULTS

Twenty six potential articles were identified from the literature search. Using the predefined inclusion and exclusion criteria, six were included in the final analysis, data extraction and data synthesis. Of these included in the review only three were prospective in design. Complete data were available for 187 of the 221 patients who underwent this treatment. The age of the participants ranged from 19 to 82 years. The fistula healing rates were reported to be between 15.8% and 72.7% at a follow-up ranging between 2 and 19 months. Early or delayed plug extrusion occurred in 16 (8.5%) of the 187 patients. Deterioration in continence was reported in 11 (5.8%) of 187 patients.

CONCLUSION

There are insufficient high-quality data on the delayed absorbable synthetic (GORE® BIO-A®) fistula plug to draw meaningful conclusions regarding its effectiveness. It does, however, appear to be a simple and safe technique associated with low complication rates and a minor deterioration in continence in a few cases.