Polymer nanomaterials for use as adjuvant surgical tools

Materials employed in the treatment of conditions encountered in surgical and clinical practice frequently face barriers in translation to application. Shortcomings can be generalized through their reduced mechanical stability, difficulty in handling, and inability to conform or adhere to complex tissue surfaces. To overcome an amalgam of challenges, research has sought the utilization of polymer-derived nanomaterials deposited in various fashions and formulations to improve the application and outcomes of surgical and clinical interventions. Clinically prevalent applications include topical wound dressings, tissue adhesives, surgical sealants, hemostats, and adhesion barriers, all of which have displayed the potential to act as superior alternatives to current materials used in surgical procedures. In this review, emphasis will be placed not only on applications, but also on various design strategies employed in fabrication. This review is designed to provide a broad and thought-provoking understanding of nanomaterials as adjuvant tools for the assisted treatment of pathologies prevalent in surgery. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanoscale Tools and Techniques in Surgery.

Controlled Release of a Therapeutic Peptide in Sprayable Surgical Sealant for Prevention of Postoperative Abdominal Adhesions

Formation of asymmetric, rigid scar tissue known as surgical adhesions is caused by traumatic disruption of mesothelial-lined surfaces in surgery. A widely adopted prophylactic barrier material (Seprafilm) for the treatment of intra-abdominal adhesions is applied operatively as a pre-dried hydrogel sheet but has reduced translational efficacy due its brittle mechanical properties. Topically administered peritoneal dialysate (Icodextrin) and anti-inflammatory drugs have failed to prevent adhesions due to an uncontrolled release profile. Hence, inclusion of a targeted therapeutic into a solid barrier host matrix with improved mechanical properties could provide dual utility in adhesion prevention and as a surgical sealant. Spray deposition of poly(lactide-co-caprolactone) (PLCL) polymer fibers through solution blow spinning has yielded a tissue-adherent barrier material with previously reported adhesion prevention efficacy due to a surface erosion mechanism that inhibits deposition of inflamed tissue. However, such an approach uniquely presents an avenue for controlled therapeutic release through mechanisms of diffusion and degradation. Such a rate is kinetically tuned via facile blending of "high" molecular weight (HMW) and "low" molecular weight (LMW) PLCL with slow and fast biodegradation rates, respectively. Here, we explore viscoelastic blends of HMW PLCL (70% w/v) and LMW PLCL (30% w/v) as a host matrix for anti-inflammatory drug delivery. In this work, COG133, an apolipoprotein E (ApoE) mimetic peptide with potent anti-inflammatory properties was selected and tested. In vitro studies with PLCL blends presented low (∼30%) and high (∼80%) percent release profiles over a 14-day period based on the nominal molecular weight of the HMW PLCL component. Two independent mouse models of cecal ligation and cecal anastomosis significantly reduced adhesion severity versus Seprafilm, COG133 liquid suspension, and no treatment control. The synergy of physical and chemical methods in a barrier material with proven preclinical studies highlights the value of COG133-loaded PLCL fiber mats in effectively dampening the formation of severe abdominal adhesions.

Clinical feasibility of absorbable gelatin film adhesion barrier (GM142 "TENALEAF®") in gynecological laparoscopic surgery: Safety assessment for first-in-human use and surgical video

AIM

To evaluate the safety and operability of the GM142 (TENALEAF®, Medical Division, Gunze Limited, Tokyo, Japan) adhesion barrier applied in patients undergoing surgery for benign gynecologic disease.

METHODS

This multicenter open study enrolled 34 patients from November 2018 to October 2019.

RESULTS

The primary outcome was the incidence of adverse events (AE) within 12 weeks postoperatively. None of the 30 patients completing the study experienced a life-threatening AE. Thirteen patients (43.3%) suffered 30 mild or moderate AE in total. No intestinal obstruction (0/30) was observed, with the sample size justified by the AdSpray® trial (8/61 patients with AE). No gelatin-specific Immunoglobulin E (IgE) antibodies were induced in the patients. The adhesion barrier could be easily inserted (even via trocar) and positioned. After malfunctions were reported in six patients, the instructions for use were updated for trocar use.

CONCLUSION

This study showed the safety and clinical feasibility GM142 as an adhesion barrier.

Short-term Outcomes and Difficulty of Repeat Laparoscopic Liver Resection

Objectives

To investigate the feasibility of repeat laparoscopic liver resection (Rep-LLR), including repeat anatomical resection (Rep-AR), as compared to initial-LLR (Ini-LLR).

Background

The indications of LLR have expanded to treatment of recurrent liver tumors. However, the feasibility of Rep-LLR, including Rep-AR, has not yet been adequately assessed.

Methods

Data of 297 patients who had undergone LLR were reviewed. Among the 297 patients, 235 (AR: 168) had undergone Ini-LLR and 62 (AR: 27) had undergone Rep-LLR, and the surgical outcomes were compared between the groups. In addition, multivariate analysis was performed to identify predictors of the difficulty of Rep-LLR based on the operation time and volume of blood loss.

Results

Of the 62 patients who had undergone Rep-LLR, 44, 14, and 4 had undergone second, third, and fourth repeat LRs, respectively. No significant intergroup differences were observed in regard to the operation time, blood loss, conversion rate to open surgery, postoperative morbidity, or postoperative hospital stay. However, the proportion of patients in whom the Pringle maneuver was used was significantly lower in the Rep-LLR group than in the Ini-LLR group. Multivariate analysis identified surgical procedure ≥sectionectomy at the initial/previous LR and an IWATE difficulty score of ≥6 as being independent predictors of the difficulty of Rep-LLR. Use of adhesion barriers at the initial/previous LR was associated with a decreased risk of failure to perform the Pringle maneuver during Rep-LLR.

Conclusions

Rep-LLR can offer outcomes comparable to those of Ini-LLR over the short term.

Sprayable tissue adhesive with biodegradation tuned for prevention of postoperative abdominal adhesions

Adhesions are dense, fibrous bridges that adjoin tissue surfaces due to uncontrolled inflammation following postoperative mesothelial injury. A widely used adhesion barrier material in Seprafilm often fails to prevent transverse scar tissue deposition because of its poor mechanical properties, rapid degradation profile, and difficulty in precise application. Solution blow spinning (SBS), a polymer fiber deposition technique, allows for the placement of in situ tissue-conforming and tissue-adherent scaffolds with exceptional mechanical properties. While biodegradable polymers such as poly(lactic-co-glycolic acid) (PLGA) have desirable strength, they exhibit bulk biodegradation rates and inflammatory profiles that limit their use as adhesion barriers and result in poor tissue adhesion. Here, viscoelastic poly(lactide-co-caprolactone) (PLCL) is used for its pertinent biodegradation mechanism. Because it degrades via surface erosion, spray deposited PLCL fibers can dissolve new connections formed by inflamed tissue, allowing them to function as an effective, durable, and easy-to-apply adhesion barrier. Degradation kinetics are tuned to match adhesion formation through the design of PLCL blends comprised of highly adhesive "low"-molecular weight (LMW) constituents in a mechanically robust "high"-molecular weight (HMW) matrix. In vitro studies demonstrate that blending LMW PLCL (30% w/v) with HMW PLCL (70% w/v) yields an anti-fibrotic yet tissue-adhesive polymer sealant with a 14-day erosion rate countering adhesion formation. PLCL blends additionally exhibit improved wet tissue adhesion strength (~10 kPa) over a 14-day period versus previously explored biodegradable polymer compositions, such as PLGA. In a mouse cecal ligation model, select PLCL blends significantly reduce abdominal adhesions severity versus no treatment and Seprafilm-treated controls.

Adhesion barriers in cardiac surgery: A systematic review of efficacy

BACKGROUND

Postoperative pericardial adhesions have been associated with increased morbidity, mortality, and surgical difficulty. Barriers exist to limit adhesion formation, yet little is known about their use in cardiac surgery. The study presented here provides the first major systematic review of adhesion barriers in cardiac surgery.

METHODS

Scopus and PubMed were assessed on November 20, 2020. Inclusion criteria were clinical studies on human subjects, and exclusion criteria were studies not published in English and case reports. Risk of bias was evaluated with the Cochrane Risk of Bias Tool. Barrier efficacy data was assessed with Excel and GraphPad Prism 5.

RESULTS

Twenty-five studies were identified with a total of 13 barriers and 2928 patients. Polytetrafluoroethylene (PTFE) was the most frequently evaluated barrier (13 studies, 67% of patients) with adhesion formation rate of 37.31% and standardized tenacity score of 26.50. Several barriers had improved efficacy. In particular, Cova CARD had a standardized tenacity score of 15.00.

CONCLUSIONS

Overall, the data varied considerably in terms of study design and reporting bias. The amount of data was also limited for the non-PTFE studies. PTFE has historically been effective in preventing adhesions. More recent barriers may be superior, yet the current data is nonconfirmatory. No ideal adhesion barrier currently exists, and future barriers must focus on the requirements unique to operating in and around the heart.

Adhesions as a risk factor for postoperative morbidity in patients undergoing repeat hepatectomy and the potential efficacy of adhesion barriers

BACKGROUND

The actual efficacy of use of adhesion barriers during liver surgery remains to be fully understood.

METHODS

We conducted an extensive review of clinical data and operation videos of 210 patients who underwent repeat hepatectomy to clarify the factors associated with the degree of adhesion as evaluated by the TORAD score.

RESULTS

Adhesion barriers were placed in 131 patients (Seprafilm^® [n = 77], Adspray^® [n = 32], and Interceed^® [n = 22)]), but not in the remaining 79 patients during the previous surgery. Multivariate analysis identified a high adhesion severity score at relaparotomy as being associated with an increased risk of postoperative global morbidity (odds ratio [OR], 1.75 per +1 point, P < .001) and major morbidity (OR, 1.88 per +1 point; P < .001), and use of an adhesion barrier at the previous surgery as being an independent predictor of a low adhesion severity score (OR, 0.21; P < .001). Use of adhesion barriers showed tendency toward lower adhesion severity scores at relaparotomy as compared to the control group, irrespective of the type of adhesion barrier used.

CONCLUSION

A high degree of adhesion formation was directly associated with an increased risk of postoperative morbidity after relaparotomy, and use of adhesion barriers appears to reduce the extent of adhesion.

Oxidized Regenerated Cellulose Sheets in Postoperative Intrathoracic Adhesions

Adhesiolysis is often necessary in intrathoracic adhesion during ipsilateral repeat lung resection. This procedure has a risk of surgical complications, including unintentional intraoperative damage of the pulmonary vessels or lung parenchyma. We used an oxidized regenerated cellulose (ORC) sheet to prevent intrathoracic adhesion after lung resection in 55 patients. The sheet was placed on the surface of the resected region and on the lung surface under the wound. No major postoperative complications were observed. Three cases underwent ipsilateral thoracic surgery for the treatment of lung malignancies, and there were no intrathoracic adhesions around the ORC sheet-covered area.

[Existing and forward-looking ways to prevent adhesions in IPOM hernia repair. A research overview]

IPOM intraperitoneal hernia repair, in comparison with other abdominal wall reconstruction methods, has a number of significant advantages. Among them are a reduction in operative time, low rate of surgical site infections, quick rehabilitation, and good cosmetic results. At the same time, one of the main constraining factors for its widespread use is the rather high frequency of adhesion formation between the implant and the abdominal organs. The first way to solve this serious problem is to improve the structure of the implant itself, and in the first place, its anti-adhesive layer. The second is the search for adjuvant tools that work in «problematic» areas, prone to adhesions formation, such as the points of implant fixation, its edges, or the areas of damage to antiadhesive layer due to a violation of the operative technique. It is desirable that they could exert their effect also in other parts of the abdominal cavity, which, despite the absence of a zone of «active» intervention, can also undergo adhesions. Based on this, the purpose of this review was to summarize modern data on the anti-adhesive activity of both composite implants and specialized membranes and liquid agents.

DendroPrime as an adhesion barrier on fracture fixation plates: an experimental study in rabbits

We tested the anti-adhesional effect of a new thiol-ene-based coating in a rabbit model. In 12 New Zealand white rabbits, the periosteum and cortex of the proximal phalanx of the second toe of both hind paws was scratched. Stainless steel plates were fixated with screws. One plate was coated with DendroPrime and the other left bare. The non-operated second toes of both hind paws of an additional four rabbits served as controls. Seven weeks after surgery, the soft tissue adhesion to the plates was evaluated macroscopically, and joint mobility was measured biomechanically. Toe joint mobility was about 20% greater and statistically significant in specimens with coated plates compared with the bare plates. Soft tissue overgrowth and, in some cases, synovitis or adhesions between the plate and the tendon were observed on all bare plates but not on any of the coated plates. We conclude that the thiol-ene-based coating can improve joint mobility by about 20%. This material has a potential to reduce adhesion around plates in fracture surgery.

Outcomes of adhesion barriers in gynecologic surgeries: A retrospective study at a medical center

During second-look surgery or hospitalization, intra-abdominal surgeries may cause severe postoperative complications, such as pelvic adhesion, postoperative ileus, and severe pain. However, only few studies have analyzed the outcomes of antiadhesive barriers in second-look surgery. This retrospective study aims to identify the outcomes of different antiadhesive barriers by analyzing surgical images. The study included patients who received an adhesion barrier during second-look surgery between January 2011 and November 2017. Four brands of adhesive barriers were used: Interceed, Seprafilm, Adept, and SurgiWrap. Adhesion scores were calculated for four quadrants of the uterus and surrounding structures before and after the use of antiadhesive barriers. The differences between the data of 2 observers and surgery times were also determined. A total of 18 patients were enrolled in the study. The adhesion scores were not significantly different before and after the placement of antiadhesive barriers. The difference in the adhesion scores between the two observers was also not significant, except in the Seprafilm group (P = .029). Furthermore, no significant change in the adhesion scores was observed between the first and second surgeries. Therefore, using adhesion barriers may not decrease the adhesion scores in the current setting.

Electrospun Water-Borne Polyurethane Nanofibrous Membrane as a Barrier for Preventing Postoperative Peritendinous Adhesion

Peritendinous adhesion is a major complication after tendon injury and the subsequent repairs or reconstructions. The degree of adhesion can be reduced by the interposition of a membranous barrier between the traumatized tendon and the surrounding tissue. In the present study, electrospun water-borne polyurethane (WPU) nanofibrous membranes (NFMs) were created for use after the reparation or reconstruction of tendons to reduce adhesion. In the electrospinning process, water was employed as the solvent for WPU, and this solvent was ecofriendly and nontoxic. The nanofibrous architecture and pore size of the WPU NFMs were analyzed. Their microporosity (0.78⁻1.05 µm) blocked the penetration of fibroblasts, which could result in adhesion and scarring around the tendon during healing. The release of WPU mimicked the lubrication effect of the synovial fluid produced by the synovium around the tendon. In vitro cell studies revealed that the WPU NFMs effectively reduced the number of fibroblasts that became attached and that there was no significant cytotoxicity. In vivo studies with the rabbit flexor tendon repair model revealed that WPU NFMs reduced the degree of peritendinous adhesion, as determined using a gross examination; a histological cross section evaluation; and measurements of the range of motion of interphalangeal joints (97.1 ± 14.7 and 79.0 ± 12.4 degrees in proximal and distal interphalangeal joints respectively), of the length of tendon excursion (11.6 ± 1.9 cm), and of the biomechanical properties.

Novel technique for adhesion barrier insertion by using cut-off surgical glove fingers in laparoscopic surgery

AIM

Laparoscopic surgery causes fewer postoperative adhesions than laparotomy and adhesion barriers are used to lessen the chance of adhesion. Sodium hyaluronate and carboxymethylcellulose (SH-CMC), a bioresorbable membrane, is effective in preventing adhesions. However, its properties make it difficult to insert the film into the abdominal cavity and to place it into the target area during laparoscopic surgeries. Here we report a novel technique for applying SH-CMC during laparoscopic surgeries by using cut-off surgical glove fingers.

METHODS

In our dry-box experiment, we found that SH-CMC became more flexible after moisturizing for 30 s. Therefore, for this procedure, we moisturizing both sides of the SH-CMC sheet (7.35 × 6.35 cm) on wet gauze (for 30 s). The film was rolled into cut-off surgical glove fingers and inserted into the abdominal cavity through a 12-mm trocar. The film was then removed from the glove finger and unrolled onto the target area (glove-finger method).

RESULTS

The dry-box experiment revealed that moisturizing both sides of SH-CMC for 30 s/side, 15 min after package removal, made the film more flexible. Ninety of 96 attempts with SH-CMC were successful among the 24 patients who underwent total laparoscopic hysterectomy with our glove-finger method.

CONCLUSION

Our glove-finger method can realize the smooth application of SH-CMC to the target area during laparoscopic surgeries.

Treatment of de-peritonealized intestine with 4DryField® PH prevents adhesions between non-resorbable intra-peritoneal hernia mesh and bowel

BACKGROUND

Intraperitoneal onlay meshes (IPOM) can be associated with intestine-to-mesh adhesion formation, implementing risks like pain, enterocutaneous fistula, infection, and female infertility. This study investigates, whether a treatment of impaired intestinum with the anti-adhesive and hemostyptic agent 4DryField^® PH prevents adhesion formation.

METHODS

In 20 male LEWIS rats uncoated polypropylene meshes were sewn to the inner abdominal wall and the cecum of the respective animal was de-peritonealized by peritoneal abrasion by a gauze swap, and meso-sutures ensured a constant contact of injured areas. Rats were treated with 4DryField^® PH gel either premixed or applied as a powder with in-situ transformation (100 mg powder plus 0.4 ml 0.9% saline solution). One week postoperatively, the extent of intestine-to-mesh adhesions and the quality of mesh ingrowth were evaluated macroscopically by two independent investigators using two scoring systems. Furthermore, specimens were analysed microscopically. All data were compared with control animals without 4DryField^® PH treatment and analysed statistically using student's t-test.

RESULTS

Treatment of de-peritonealised cecum with 4DryField^® PH significantly reduced intestine-to-mesh adhesions in both treatment groups as compared to controls without 4DryField^® PH treatment (68% reduction with premixed gel, P<0.0001; 80% reduction with in-situ gel, P<0.0001). There was no impact on the quality of mesh ingrowth, confirmed histologically by a single-layer mesothelial coverage.

CONCLUSION

These experiments mimick clinical IPOM implantation scenarios with adjacent bowel depleted from peritoneum. 4DryField^® PH gel treatment resulted in intestinal mesothelial surface recovering without development of bowel-to-mesh adhesions. Concurrently, integration of mesh into the abdominal wall is undisturbed by 4DryField^® PH treatment.

Effectiveness and short-term safety of modified sodium hyaluronic acid-carboxymethylcellulose at cesarean delivery: a randomized trial

BACKGROUND

The rising cesarean birth rate has drawn attention to risks associated with repeat cesarean birth. Prevention of adhesions with adhesion barriers has been promoted as a way to decrease operative difficulty. However, robust data demonstrating effectiveness of such interventions are lacking.

OBJECTIVE

We report data from a multicenter trial designed to evaluate the short-term safety and effectiveness of a modified sodium hyaluronic acid (HA)-carboxymethylcellulose (CMC) absorbable adhesion barrier for reduction of adhesions following cesarean delivery.

STUDY DESIGN

Patients who underwent primary or repeat cesarean delivery were included in this multicenter, single-blinded (patient), randomized controlled trial. Patients were randomized into either HA-CMC (N = 380) or no treatment (N = 373). No other modifications to their treatment were part of the protocol. Short-term safety data were collected following randomization. The location and density of adhesions (primary outcome) were assessed at their subsequent delivery using a validated tool, which can also be used to derive an adhesion score that ranges from 0-12.

RESULTS

No differences in baseline characteristics, postoperative course, or incidence of complications between the groups following randomization were noted. Eighty patients from the HA-CMC group and 92 controls returned for subsequent deliveries. Adhesions in any location were reported in 75.6% of the HA-CMC group and 75.9% of the controls (P = .99). There was no significant difference in the median adhesion score; 2 (range 0-10) for the HA-CMC group vs 2 (range 0-8) for the control group (P = .65). One third of the HA-CMC patients met the definition for severe adhesions (adhesion score >4) compared to 15.5% in the control group (P = .052). There were no significant differences in the time from incision to delivery (P = .56). Uterine dehiscence in the next pregnancy was reported in 2 patients in HA-CMC group vs 1 in the control group (P = .60).

CONCLUSION

Although we did not identify any short-term safety concerns, HA-CMC adhesion barrier applied at cesarean delivery did not reduce adhesion formation at the subsequent cesarean delivery.

Ionically cross-linked hyaluronic acid: wetting, lubrication, and viscoelasticity of a modified adhesion barrier gel

Hyaluronic acid (HA), in linear or cross-linked form, is a common component of cosmetics, personal care products, combination medical products, and medical devices. In all cases, the ability of the HA solution or gel to wet surfaces and/or disrupt and lubricate interfaces is a limiting feature of its mechanism of action. We synthesized ferric ion-cross-linked networks of HA based on an adhesion barrier, varied the degree of cross-linking, and performed wetting goniometry, viscometry, and dynamic mechanical analysis. As cross-linking increases, so do contact angle, viscosity, storage modulus, and loss modulus; thus, wetting and lubrication are compromised. These findings have implications in medical device materials, such as adhesion barriers and mucosal drug delivery vehicles.

Evaluation of Perivascular Adhesion Formation in New Zealand White Rabbits Using Oxiplex and DuraSeal Xact Adhesion Barrier System

Background

Adhesion formation after spine surgery is a result of normal wound healing that may place patients at increased risk for complications during revision surgery. Preventing adhesions could reduce the risk of complications during revision surgery, and possibly reduce the need for revision procedures. This study evaluates the ability of DuraSeal Xact Adhesion Barrier System (DSX) (Covidien, Mansfield, Massachusetts) and Oxiplex/SP gel (OX) (FzioMed, San Luis Obispo, California) to affect the extent and severity of postoperative perivascular adhesion development in an anterior spinal surgical rabbit model.

Methods

We determined the extent and severity of postoperative adhesion development 34 days after surgery in 12 male New Zealand White rabbits randomly assigned to intraoperative treatment with either DSX or OX, or to an untreated control group. Adhesion severity and extent were scored on scale from 0 (none) to 3 (severe).

Results

The extent and severity of adhesions in the DSX group were significantly less than in the untreated control group. The DSX group mean extent score was 1.3 ± 0.5 (vs 2.5, P = .01) and the mean severity score was 1.25 ± 0.5 (vs 2.8, P = .005). The extent and severity of adhesions in the OX group were not significantly different from the control group.

Conclusion

In this study, we found DSX to be the most effective compound in preventing adhesion formation after anterior spine surgery.

Clinical Relevance

Extrapolating these results in rabbits to humans, less scarring between the major blood vessels could decrease the rate of complications in revision spine procedures.