Materials in Surgery: A Review of Biomaterials in Postsurgical Tissue Adhesion and Seroma Prevention

Effectiveness of 5-Fluorouracil and Hypertonic Glucose in the Prevention of Post-mastectomy Seroma in an Experimental Animal Model

INTRODUCTION

Seroma is a frequent complication that can affect the final result of reconstructive and cosmetic surgeries.

METHODOLOGY

This study evaluated the effectiveness of 5-Fluorouracil and 75% hypertonic glucose in preventing seroma in a mastectomy rat model, as well as cellular and vascular events in adjacent tissues. A left mastectomy with lymphadenectomy was performed in 60 Wistar-Albino female rats. Animals randomly allocated to the control group (Group I; n = 20) were sutured right after mastectomy. The intervention groups received 1.0 mL of 75% hypertonic glucose (Group II; n = 20) or 1.0 mL of 5-Fluorouracil (Group III; n = 20) at the surgical site before suturing. The assessment of the presence of seroma was performed in all animals at 24, 48, and 72 h and on the 7th and 12th postoperative day. After the 12th day, a tissue sample was taken from the surgical site and sent for histological analysis. The occurrence of seroma was assessed using GEE. A significance level of 5% was adopted.

RESULTS

Differences in seroma formation over time were observed for both Control Group I (p=0.041) and Intervention Group II (p<0.001). In Intervention Group III, there was no difference in the percentage and volume of seroma across the assessment points (p=0.627). When both the Control and Intervention Group II were compared to Intervention Group III, we found a reduction in seroma formation in the last group. The reduction in the inflammatory process was more regular to Intervention Group III.

CONCLUSION

In this animal model, 5-Fluorouracil was more effective in preventing seroma formation than 75% Hypertonic Glucose. No Level Assigned This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Self-healing, injectable hydrogel based on dual dynamic covalent cross-linking against postoperative abdominal cavity adhesion

Clinically, increasing the peritoneal barrier is an effective adjunct to reducing postoperative peritoneal adhesion. This study presents a facile template for preparing a supramolecular hybrid hydrogel through dynamic covalent cross-linking between carboxymethyl chitosan (CMCS), 2-formylphenylboronic acid (2-FPBA), and quercetin (Que). The as-prepared complex CMCS/2-FPBA/Que (CFQ) hydrogel exhibited favorable antibacterial, anti-inflammatory, and antioxidant effects. A L929 cytotoxicity evaluation confirmed the favorable cytocompatibility of the CFQ hydrogel. The postoperative anti-adhesion ability of the CFQ hydrogel was further evaluated in rats with lateral wall defects and cecal abrasions. Compared with control groups, the tissue adhesion rate was significantly reduced by increasing the Que concentration in all the hydrogel-treated groups. Additionally, the sustained-release time of the C3F0.8Q0.08 hydrogel can exceed 14 days, which is highly desirable for clinical wound treatment. STATEMENT OF SIGNIFICANCE: Postoperative adhesions are a very common postoperative complication that seriously affects the quality of life of patients. The currently commonly used methods for preventing adhesion mainly use degradable barrier materials for physical separation. In this study, we prepared a dual dynamic covalently cross-linked CFQ hydrogel, which is not only degradable and injectable, but also has multiple properties such as antibacterial, antioxidant and anti-inflammatory, which can effectively prevent postoperative adhesion and promote wound healing.

Anti-Adhesion Effect of Composite Film Materials Based on Glycoluril-Modified Sodium Carboxymethyl Cellulose

The aim of the study was to develop composite film materials derived from modified sodium carboxymethyl cellulose and to evaluate their anti-adhesive effects.

Lysine-urethane-based tissue adhesion for mastectomy-an approach to reducing the seroma rate?

Purpose

Postoperative seromas are a problem in the surgical treatment of breast cancer. The aim of the study was to evaluate whether the lysine-urethane-based tissue adhesive TissuGlu^® without drainage is equal/ non-inferior to standard mastecomy with drainage.

Methods

The study was designed as a prospective, randomized, multicentre non-inferiority study comparing the use of TissuGlu^® without drainage with standard wound care with a drain insertion in ablative breast procedures. The number of clinical interventions, quality of life and wound complications were followed-up for 90 days in both groups.

Results

Although the statistical power was not reached, twice as many clinical interventions were performed in the TissuGlu^® group than in the drainage group, especially aspirations of clinically relevant seromas (p = 0.014). The TissuGlu^® group produced overall less wound fluid, but developed a clinically relevant seroma (100% vs. 63%) which made an intervention necessary. Less hospitalisation time was observed in the TissuGlu^® group, but the complication rate was higher. There was no significant difference in regards to postoperative pain. In summary the non-inferiority of TissuGlu^® compared to standard drainage couldn’t be reached.

Discussion

The present evaluation shows no advantage of the tissue adhesive TissuGlu^® in terms of seroma formation and frequency of intervention compared to a standard drainage for mastectomies, but the shorter inpatient stay certainly has a positive effect on the quality of life.

How Much Blood Could a JP Suck If a JP Could Suck Blood?

OBJECTIVE

Active surgical drains minimize fluid accumulation in the postoperative period. The Jackson-Pratt (JP) system consists of a silicone drain connected by flexible tubing to a bulb. When air in the bulb is evacuated, negative pressure is applied at the surgical site to aspirate fluid. The objective of this study was to determine if the evacuation method and volume of accumulated fluid affect the pressure generated by the bulb.

METHODS

Bulbs were connected to a digital manometer under various experimental conditions. A random number generator determined the initial evacuation method for each bulb, either side-in or bottom-up. Subsequent evacuations were alternated until data was collected in triplicate for each method. Predetermined amounts of water were placed into the bulb; air was evacuated; and pressure was recorded. The digital manometer was allowed to equilibrate for 1 minute prior to data acquisition.

RESULTS

The average amount of pressure after a side-in evacuation of a JP bulb was 87.4 cm H₂ O compared to 17.7 cm H₂ O for a bottom-up evacuation (P < 0.0001). When the drain contained 25 mL, 50 mL, 75 mL, and 100 mL of fluid, the pressure applied dropped to 72.6, 41.3, 37.0, and 35.6 cm H₂ O, respectively.

CONCLUSIONS

JP drains generate negative pressure in order to reduce fluid accumulation at surgical sites. Although its function is frequently taken for granted, this study demonstrates that both the specific method for evacuating the bulb as well as the amount of fluid in the bulb significantly affect the performance of this device.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:1806-1809, 2019.

Bioadhesives for internal medical applications: A review

Bioadhesives such as tissue adhesives, hemostatic agents, and tissue sealants have gained increasing popularity in different areas of clinical operations during the last three decades. Bioadhesives can be categorized into internal and external ones according to their application conditions. External bioadhesives are generally applied in topical medications such as wound closure and epidermal grafting. Internal bioadhesives are mainly used in intracorporal conditions with direct contact to internal environment including tissues, organs and body fluids, such as chronic organ leak repair and bleeding complication reduction. This review focuses on internal bioadhesives that, in contrast with external bioadhesives, emphasize much more on biocompatibility and adhesive ability to wet surfaces rather than on gluing time and intensity. The crosslinking mechanisms of present internal bioadhesives can be generally classified as follows: 1) chemical conjugation between reactive groups; 2) free radical polymerization by light or redox initiation; 3) biological or biochemical coupling with specificity; and 4) biomimetic adhesion inspired from natural phenomena. In this review, bioadhesive products of each class are summarized and discussed by comparing their designs, features, and applications as well as their prospects for future development.

STATEMENT OF SIGNIFICANCE

Despite the emergence of numerous novel bioadhesive formulations in recent years, thus far, the classification of internal and external bioadhesives has not been well defined and universally acknowledged. Many of the formulations have been proposed for treatment of several diseases even though they are not applicable for such conditions. This is because of the lack of a systematic standard or evaluation protocol during the development of a new adhesive product. In this review, the definition of internal and external bioadhesives is given for the first time, and with a focus on internal bioadhesives, the criteria of an ideal internal bioadhesive are adequately discussed; this is followed by the review of recently developed internal bioadhesives based on different gluing mechanisms.

Econazole-releasing porous space maintainers for fungal periprosthetic joint infection

While antibiotic-eluting polymethylmethacrylate space maintainers have shown efficacy in the treatment of bacterial periprosthetic joint infection and osteomyelitis, antifungal-eluting space maintainers are associated with greater limitations for treatment of fungal musculoskeletal infections including limited elution concentration and duration. In this study, we have designed a porous econazole-eluting space maintainer capable of greater inhibition of fungal growth than traditional solid space maintainers. The eluted econazole demonstrated bioactivity in a concentration-dependent manner against the most common species responsible for fungal periprosthetic joint infection as well as staphylococci. Lastly, these porous space maintainers retain compressive mechanical properties appropriate to maintain space before definitive repair of the joint or bony defect.

A postoperative anti-adhesion barrier based on photoinduced imine-crosslinking hydrogel with tissue-adhesive ability

Postoperative adhesion is a serious complication that can further lead to morbidity and/or mortality. Polymer anti-adhesion barrier material provides an effective precaution to reduce the probability of postoperative adhesion. Clinical application requires these materials to be easily handled, biocompatible, biodegradable, and most importantly tissue adherent to provide target sites with reliable isolation. However, currently there is nearly no polymer barrier material that can fully satisfy these requirements. In this study, based on the photoinduced imine-crosslinking (PIC) reaction, we had developed a photo-crosslinking hydrogel (CNG hydrogel) that composed of o-nitrobenzyl alcohol (NB) modified carboxymethyl cellulose (CMC-NB) and glycol chitosan (GC) as an anti-adhesion barrier material. Under light irradiation, CMC-NB generated aldehyde groups which subsequently reacted with amino groups distributed on GC or tissue surface to form a hydrogel barrier that covalently attached to tissue surface. Rheological analysis demonstrated that CNG hydrogel (30mg/mL polymer content) could be formed in 30s upon light irradiation. Tissue adhesive tests showed that the tissue adhesive strength of CNG hydrogel (30mg/mL) was about 8.32kPa-24.65kPa which increased with increasing CMC-NB content in CNG hydrogel. Toxicity evaluation by L929 cells demonstrated that CNG hydrogel was cytocompatible. Furthermore, sidewall defect-cecum abrasion model of rat was employed to evaluate the postoperative anti-adhesion efficacy of CNG hydrogel. And a significantly reduction of tissue adhesion (20% samples with low score adhesion) was found in CNG hydrogel treated group, compared with control group (100% samples with high score adhesion). In addition, CNG hydrogel could be degraded in nearly 14days and showed no side effect on wound healing. These findings indicated that CNG hydrogel can effectively expanded the clinical treatments of postoperative tissue adhesion.

STATEMENT OF SIGNIFICANCE

In this study, a tissue adhesive photo-crosslinking hydrogel (CNG) was developed based on photo-induced imine crosslinking reaction (PIC) for postoperative anti-adhesion. CNG hydrogel showed the features of easy and convenient operation, fast and controllable gelation, suitable gel strength, good biocompatibility, and most importantly strong tissue adhesiveness. Therefore, it shows very high performance to prevent postoperative tissue adhesion. Overall, our study provides a more suitable hydrogel barrier material that can overcome the shortcomings of current barriers for clinical postoperative anti-adhesion.

Prospective randomized controlled study to assess the value of a hemostatic and sealing agent for preventing seroma after axillary lymphadenectomy

BACKGROUND AND OBJECTIVES

Postoperative seroma after axillary lymphadenectomy leads to an increased use of resources and an impaired quality of life of patients. This randomized clinical trial was designed to assess the value of a hemostatic and sealing agent for decreasing seroma occurrence after axillary lymphadenectomy.

METHODS

A prospective, randomized, blind study was conducted on 91 axillary lymphadenectomies distributed into a control group (n = 47) and a test group in which a collagen sponge coated with human coagulation factors was used (n = 44). Primary end-points were number of days before removal of axillary drainage, axillary drainage output, and occurrence of seroma, wound infection, haematoma, or wound dehiscence, within 8 weeks of surgery. Bivariate and multivariate analyses on seroma occurrence were performed.

RESULTS

Seroma occurred in 29 patients (31.86%). A significant direct relationship (P = 0.002) was only noted between use of the hemostatic and sealing agent and nonoccurrence of seroma. In the multivariate study, the only variable found to be significantly related to seroma occurrence was use of the above agent (P = 0.046; odds ratio: 3.365 [95%CI: 1.024-11.060]).

CONCLUSIONS

Use of a collagen sponge coated with human coagulation factors following axillary lymphadenectomy was associated to a lower incidence of postoperative seroma. J. Surg. Oncol. 2016;114:423-427. © 2016 Wiley Periodicals, Inc.

Adhesion Prevention after Laminectomy Using Silk-Polyethylene Glycol Hydrogels

Laminectomy is a common operation in spine surgery to reduce spinal cord and nerve pressure. However, scar tissues often form in the spinal canal and adhere to the dura surface, resulting in low back pain postsurgery. In the present study, biodegradable silk-polyethylene glycol (PEG) hydrogels are evaluated for adhesion prevention after laminectomies in New Zealand rabbits, with nondegradable expanded polytetrafluoroethylene (ePTFE) membranes and saline as controls. No significant difference among the three groups is observed within 2 weeks. Silk is fully degraded within 6 weeks, leaving a gap separating the scar tissue and the dura mater. Severe dural scar adhesion form in the saline control group after 8 weeks, while no or mild adhesion is observed in the ePTFE membrane and silk-PEG hydrogel samples. Human dermal fibroblasts (HS-865-SK cells) are cultured in the silk-PEG hydrogel extracts and on top of gel surfaces. Compared to the controls of tissue culture plate (no silk) and sonicated silk hydrogels (no PEG), the proliferation of fibroblasts in both conditions is significantly reduced initially but resumes after 120 h, suggesting the surface properties of the hydrogels and local, temporal release of PEG accounts for the adhesion prevention observed in vivo in this study.

Binding of Anticell Adhesive Oxime-Crosslinked PEG Hydrogels to Cardiac Tissues

Postsurgical cardiac adhesions increase the number of surgeries as well as patient mortality and morbidity. A fast gelling oxime-crosslinked PEG hydrogel with tunable gelation time, degradation, and mechanical properties is presented. This material is cytocompatible and prevents cellular adhesion. Material retention on different cardiac tissues is demonstrated ex vivo over time and that functional group ratio alters material retention on different cardiac tissues.

Comparative stability of the bioresorbable ferric crosslinked hyaluronic acid adhesion prevention solutions

The Intergel® ferric crosslinked hyaluronate (FeHA) adhesion prevention solution (APS) (FDA) is associated with serious post-operative complications (Henley, http://www.lawyersandsettlements.com/features/gynecare-intergel/intergel-timeline.html, 2007; FDA, 2003; Roman et al., Fertil Steril 2005, 83 Suppl 1:1113-1118; Tang et al., Ann Surg 2006;243(4):449-455; Wiseman, Fertil Steril 2006;86(3):771; Wiseman, Fertil Steril 2006;85(4):e7). This prompted us to examine the in situ stability of crosslinked HA materials to hyaluronidase lyase degradation. Variables such as ferric ionic crosslink density, HA concentration, gel geometry, and molecular weight (MW) of HA polymer were studied. Various formulations of the crosslinked "in house" [Isayeva et al., J Biomed Mater Res: Part B - Appl Biomater 2010, 95B (1):9-18] FeHA (0.5%, w/v; 30, 50, 90% crosslinked), the Intergel® FeHA (0.5%, w/v; 90%), and the non-crosslinked HA (0.05-0.5%, w/v) were degraded at a fixed activity of hyaluronidase lyase from Streptomyces hyalurolyticus (Hyase) at 37°C over time according to the method [Payan et al., J Chrom B: Biomed Sci Appl 1991;566(1):9-18]. Under our conditions, the data show that the crosslink density affects degradation the most, followed by HA concentration and then gel geometry. We found that MW has no effect. Our results are one possible explanation of the observations that the Intergel® FeHA APS (0.5%, w/v; 90%) material persisted an order of magnitude longer than expected [t1/2 = 500 hrs vs. t1/2 = 50 hrs (FDA; Johns et al., Fertil Steril 1997;68(1):37-42)]. These data also demonstrate the sensitivity of the in vitro hyaluronidase assay to predict the in situ stability of crosslinked HA medical products as previously reported [Sall et al., Polym Degrad Stabil 2007;92(5):915-919].

Optimizing the closed suction surgical drainage system

BACKGROUND

Closed suction drains are indicated in a wide array of postoperative settings, with many distinct drainage systems available to the surgeon. The purpose of this study was to compare the suction gradients achieved using 2 different sizes of suction reservoirs and 2 different techniques for generating negative pressure.

MATERIALS AND METHODS

Drainage reservoirs of 100 and 400 ml were chosen to evaluate their ability to achieve suction. Suction was established in both sizes of drains by pressing the sides of the reservoir together or by pushing the bottom of the reservoir toward the top. Negative pressures were recorded with the reservoir empty, and after every 10-ml addition of saline. Averages were graphed to illustrate the applied suction over a range of drain volumes.

RESULTS

The 100-ml drainage system reached a peak suction of -117.6 mmHg, while the 400-ml drainage system reached only a peak suction of -71.4 mmHg. Both of the maximum suction readings were achieved using the full-squeeze technique. The bottom-pushed-in technique did not result in any sustained measurable levels of suction using either of the reservoir volumes.

CONCLUSIONS

Smaller drain reservoirs are more successful in generating a high initial suction than larger reservoirs, especially when the volume of fluid in the drain is relatively low. In all sizes of drains, compressing the sides of the reservoir is a far better technique for establishing negative pressure than pressing the bottom of the drain up toward the top.

Design strategies and applications of tissue bioadhesives

In the past two decades tissue adhesives and sealants have revolutionized bleeding control and wound healing. This paper focuses on existing tissue adhesive design, their structure, functioning mechanism, and their pros and cons in wound management. It also includes the latest advances in the development of new tissue adhesives as well as the emerging applications in regenerative medicine. We expect that this paper will provide insightful discussion on tissue bioadhesive design and lead to innovations for the development of the next generation of tissue bioadhesives and their related biomedical applications.

Prevention of seroma formation with TissuGlu® surgical adhesive in a canine abdominoplasty model: long term clinical and histologic studies

BACKGROUND

Seroma formation is a common postoperative complication following many surgical procedures including abdominoplasty. Recently, a lysine-derived urethane (LDU) surgical adhesive was shown to prevent seroma formation in short term studies in a canine model of abdominoplasty. This current study evaluates efficacy of the adhesive (TissuGlu®, Cohera Medical, Inc.) in the same model at longer time points, and examines the histological tissue response to extended exposure to the adhesive.

MATERIALS AND METHODS

Bilateral subcutaneous pockets were created in the ventrolateral abdominal wall and additional tissue damage was inflicted using electrocautery. On one side, the tissue layers were treated with the adhesive prior to closure, whereas the control side received no treatment prior to standard closure of the incision. Seroma fluid accumulation was measured and histologic analysis was performed at 3 and 12 weeks.

RESULTS

Seroma formation (mean±SD, 690±870 ml; median volume of 348.5 ml) was observed on the control side, whereas the treated side had adherence between the tissue layers, and minimal if any fluid accumulation (mean±SD, 44±53 ml; median volume of 15 ml) (p<0.01) (n=8) at 3 week necropsy. In animals survived to 12 weeks, two of the four control sides required aspiration of serous fluid, and dead space persisted for the entirety of the study in one animal. For the adhesive treated sites, none of the four animals showed signs of seroma at euthanasia, although serial aspiration was performed in one treatment site within the first month and resulted in resolution of the process. The adhesive was detected in the surgical site at 3 and 12 weeks, and independent histological analysis found it to be a non-irritant compared to control (no treatment).

CONCLUSIONS

Long term evaluation of TissuGlu® Surgical Adhesive showed that it is capable of preventing the formation of seroma in this canine abdominoplasty model, indicating that it may be of clinical benefit in the prevention of seroma formation in patients undergoing abdominoplasty.

Adhesion prevention in patients with multiple cesarean deliveries

Adhesion formation is a well-known complication of abdominal surgery. Although one third of all deliveries in the United States are by cesarean delivery (CD), little is known about adhesions in the obstetric setting. Various surgical techniques for reducing adhesion formation following CD have been investigated. The relative benefits of peritoneal closure and single-layer uterine closure are areas of continued research and debate. Adhesion prevention products are also becoming more commonplace in gynecologic surgery. Two membrane/adhesion barriers have been approved in the United States. A barrier consisting of oxidized regenerated cellulose (Interceed absorbable adhesion barrier) has been shown to reduce adhesions during microsurgery. Its use may be limited following CD because complete hemostasis is crucial to its efficacy. Seprafilm adhesion barrier, composed of hyaluronic acid and carboxymethylcellulose, is approved for use in abdominal or pelvic laparotomy. Preliminary data suggest that it may be effective for reducing adhesions following CD. This article discusses what is currently known about adhesion prevention in the obstetric population and highlights the paucity of level I evidence available to clinicians in this setting.

Biodegradable and thermoreversible PCLA-PEG-PCLA hydrogel as a barrier for prevention of post-operative adhesion

Biodegradable polymers can serve as barriers to prevent the post-operative intestinal adhesion. Herein, we synthesized a biodegradable triblock copolymer poly(ɛ-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(ɛ-caprolactone-co-lactide) (PCLA-PEG-PCLA). The concentrated polymeric aqueous solution was injectable, and a hydrogel could be rapidly formed due to percolation of a self-assembled micelle network at the body temperature without requirement of any chemical reactions. This physical hydrogel retained its integrity in vivo for a bit more than 6 weeks and was eventually degraded due to hydrolysis. The synthesized polymer exhibited little cytotoxicity and hemolysis; the acute inflammatory response after implanting the hydrogel was acceptable, and the degradation products were less acidic than those of other polyester-containing materials. A rabbit model of sidewall defect-bowel abrasion was employed, and a significant reduction of post-operative peritoneal adhesion has been found in the group of in situ formed PCLA-PEG-PCLA hydrogels.

Adverse effects of polyvinylidene fluoride-coated polypropylene mesh used for laparoscopic intraperitoneal onlay repair of incisional hernia

BACKGROUND

Polyvinylidene fluoride-coated polypropylene meshes have been developed specifically for intraperitoneal onlay mesh repair. They combine a macroporous design with biomechanical characteristics compatible with the abdominal wall and are reported to have favourable antiadhesive properties. This retrospective study reports complications related to one of these materials, DynaMesh.

METHODS

Twenty-nine patients underwent intraperitoneal onlay mesh repair with DynaMesh at one of two hospitals. Patients characteristics, surgical procedures and postoperative analgesia were comparable at both sites.

RESULTS

Six patients developed DynaMesh-related complications that required surgical reintervention by laparotomy within 1 year of operation. Surgical reintervention was for adhesions in five patients and the mesh had to be explanted in three. One mesh was explanted because of early infection. Adhesions to DynaMesh were found in two patients who had surgery for unrelated reasons.

CONCLUSION

Laparoscopic intraperitoneal onlay DynaMesh repair was associated with a high rate of complications.

Block copolymers for the rational design of self-forming postsurgical adhesion barriers

Post-surgical adhesions, abnormal fibrous linkages between adjacent tissue surfaces, represent one of the most common and significant complications facing surgical recovery today. Physical barriers and gels have been the most successful at limiting their formation, yet are not effective in cases where the pro-adhesive site is either unknown or difficult to reach (e.g. during laparoscopic surgery). In this work, poly(methacrylic acid-co-t-butylmethacrylate)-b-poly(ethylene glycol (M(N) = 1000) methacrylate) diblock and statistical copolymers were synthesized as a platform for designing self-forming adhesion barriers, which can attach to exposed pro-adhesive sites through binding with the positively charged extracellular matrix, basement membrane proteins and deposited fibrin. An experimental model based upon a quartz crystal microbalance with dissipation was developed to test the diblock copolymers ability (i) to adsorb to an amine-terminated self-assembled monolayer, and (ii) to inhibit subsequent protein adsorption. These results were also confirmed using an in vitro cell attachment model. As the mole fraction of methacrylic acid content increased, polymer adsorption increased. All synthesized diblock copolymers investigated provided high resistance to protein adsorption, with blockade ranging from 55% to 81%. Except for the uncharged control polymers, the ability of these materials to resist cellular attachment showed similar trends, with the suppression of attachment approaching 75%. Energy dissipation analysis and variable-angle spectroscopic ellipsometry revealed two competing adsorption mechanisms depending on the molecular properties of the polymer.