Injectable drug-eluting elastomeric polymer: a novel submucosal injection material

Injectable chitosan-polyvinylpyrrolidone composite thermosensitive hydrogels with sustained submucosal lifting for endoscopic submucosal dissection

To develop a submucosal injection material with sustained submucosal lifting for endoscopic submucosal dissection (ESD), this study designed and prepared a novel composite thermosensitive hydrogel system with high pH chitosan-polyvinylpyrrolidone-β-glycerophosphate (HpHCS-PVP-GP). HpHCS improved the injectability of the hydrogels and retained the rapid gelation ability at low concentrations. The modification of PVP significantly improved the stability of low-temperature hydrogel precursor solutions and the integrity of hydrogels formed at 37 °C through hydrogen bonds between PVP and HpHCS. A mathematical model was established using response surface methodology (RSM) to evaluate the synergistic effect of HpHCS, GP, and PVP concentrations on gelation time. This RSM model and submucosal lifting evaluation using in vitro pig esophageal models were used to determine the optimal formula of HpHCS-PVP-GP hydrogels. Although the higher PVP concentration (5 % (w/v)) prolonged gelation time, it improved hydrogel mechanical strength, resulting in better submucosal lifting performance. The experiments of Bama mini pigs showed that the heights of the cushions elevated by the HpHCS-5%PVP-GP hydrogel remained about 80 % 1 h after injection. Repeated injections were avoided, and the hydrogel had no cytotoxicity after electric cutting. Therefore, the HpHCS-PVP-GP thermosensitive hydrogel might be a promising submucosal injection material for ESD.

Nanodrugs systems for therapy and diagnosis of esophageal cancer

With the increasing incidence of esophageal cancer, its diagnosis and treatment have become one of the key issues in medical research today. However, the current diagnostic and treatment methods face many unresolved issues, such as low accuracy of early diagnosis, painful treatment process for patients, and high recurrence rate after recovery. Therefore, new methods for the diagnosis and treatment of esophageal cancer need to be further explored, and the rapid development of nanomaterials has brought new ideas for solving this problem. Nanomaterials used as drugs or drug delivery systems possess several advantages, such as high drug capacity, adjustably specific targeting capability, and stable structure, which endow nanomaterials great application potential in cancer therapy. However, even though the nanomaterials have been widely used in cancer therapy, there are still few reviews on their application in esophageal cancer, and systematical overview and analysis are deficient. Herein, we overviewed the application of nanodrug systems in therapy and diagnosis of esophageal cancer and summarized some representative case of their application in diagnosis, chemotherapy, targeted drug, radiotherapy, immunity, surgery and new therapeutic method of esophageal cancer. In addition, the nanomaterials used for therapy of esophageal cancer complications, esophageal stenosis or obstruction and oesophagitis, are also listed here. Finally, the challenge and the future of nanomaterials used in cancer therapy were discussed.

A review of hydrogels used in endoscopic submucosal dissection for intraoperative submucosal cushions and postoperative management

Endoscopic submucosal dissection (ESD) has been clinically proved to have prominent advantages in the treatment of early gastrointestinal cancers over traditional surgery, including less trauma, fewer complications, a quicker recovery and lower costs. During the procedure of ESD, appropriate and multifunctional submucosal injected materials (SIMs) as submucosal cushions play an important role, however, even with many advances in design strategies of SIMs over the past decades, the performance of the submucosal cushions with postoperative management function seems to be still unsatisfactory. In this review, we gave a brief historical recount about the clinical development of SIMs, then some common applications of hydrogels used as SIMs in ESD were summarized, while an account of the universal challenges during ESD procedure was also outlined. Going one step further, some cutting-edge functional strategies of hydrogels for novel applications in ESD were exhibited. Finally, we concluded the advantages of hydrogels as SIMs for ESD as well as the treatment dilemma clinicians faced when it comes to deeply infiltrated lesions, some technical perspectives about linking the clinical demand with commercial supply were also proposed. Encompassing the basic elements of SIMs used in ESD surgery and the corresponding postoperative management requirements, this review could be a good reference for relevant practitioners in expanding the research horizon and improving the well-being index of patients.

Endoscopically injectable and self-crosslinkable hydrogel-mediated stem cell transplantation for alleviating esophageal stricture after endoscopic submucosal dissection

Esophageal stricture after extensive endoscopic submucosal dissection impairs the quality of life of patients with superficial esophageal carcinoma. Beyond the limitations of conventional treatments including endoscopic balloon dilatation and the application of oral/topical corticosteroids, several cell therapies have been recently attempted. However, such methods are still limited in clinical situations and existing setups, and the efficacies are less in some cases since the transplanted cells hardly remain at the resection site for a long time due to swallowing and peristalsis of the esophagus. Thus, a cell transplantation platform directly applicable with clinically established equipment and enabling stable retention of transplanted cells can be a promising therapeutic option for better clinical outcomes. Inspired by ascidians that rapidly self-regenerate, this study demonstrates endoscopically injectable and self-crosslinkable hyaluronate that allows both endoscopic injection in a liquid state and self-crosslinking as an in situ-forming scaffold for stem cell therapy. The pre-gel solution may compatibly be applied with endoscopic tubes and needles of small diameters, based on the improved injectability compared to the previously reported endoscopically injectable hydrogel system. The hydrogel can be formed via self-crosslinking under in vivo oxidative environment, while also exhibiting superior biocompatibility. Finally, the mixture containing adipose-derived stem cells and the hydrogel can significantly alleviate esophageal stricture after endoscopic submucosal dissection (75% of circumference, 5 cm in length) in a porcine model through paracrine effects of the stem cell in the hydrogel, which modulate regenerative processes. The stricture rates on Day 21 were 79.5% ± 2.0%, 62.8% ± 1.7%, and 37.9% ± 2.9% in the control, stem cell only, and stem cell-hydrogel groups, respectively (p < 0.05). Therefore, this endoscopically injectable hydrogel-based therapeutic cell delivery system can serve as a promising platform for cell therapies in various clinically relevant situations.

Injectable shear-thinning sodium alginate hydrogels with sustained submucosal lift for endoscopic submucosal dissection

Endoscopic submucosal dissection (ESD) is one of the most effective approaches for the minimally invasive treatment of early gastrointestinal cancers. Submucosal injections help safely and successfully remove lesions during ESD by elevating the mucosa and separating the submucosal muscle layer. Herein, we report dynamic injectable sodium alginate hydrogels (ISAHs) with shear-thinning for ESD surgery, which were easily fabricated by the sulfhydryl group of GSH-modified sodium alginate (SA-GSH) reacting with the aldehyde group of oxidized sodium alginate (OSA) at room temperature. ISAHs have advantageous self-healing abilities and antioxidant activity. Additionally, according to an in vitro test on porcine colorectal submucosal lifting, the submucosal elevation heights created by ISAHs were 13 % -18 % greater than those created by commercial ESD solutions (0.4 w/v% sodium hyaluronate). These properties and biocompatibility were confirmed in vitro and in vivo experiments. ISAHs will hopefully become a novel submucosal injectable hydrogel to assist ESD surgery.

Development of Biodegradable Osteopromotive Citrate-Based Bone Putty

The burden of bone fractures demands development of effective biomaterial solutions, while additional acute events such as noncompressible bleeding further motivate the search for multi-functional implants to avoid complications including osseous hemorrhage, infection, and nonunion. Bone wax has been widely used in orthopedic bleeding control due to its simplicity of use and conformation to irregular defects; however, its nondegradability results in impaired bone healing, risk of infection, and significant inflammatory responses. Herein, a class of intrinsically fluorescent, osteopromotive citrate-based polymer/hydroxyapatite (HA) composites (BPLP-Ser/HA) as a highly malleable press-fit putty is designed. BPLP-Ser/HA putty displays mechanics replicating early nonmineralized bone (initial moduli from ≈2-500 kPa), hydration induced mechanical strengthening in physiological conditions, tunable degradation rates (over 2 months), low swelling ratios (<10%), clotting and hemostatic sealing potential (resistant to blood pressure for >24 h) and significant adhesion to bone (≈350-550 kPa). Simultaneously, citrate's bioactive properties result in antimicrobial (≈100% and 55% inhibition of S. aureus and E. coli) and osteopromotive effects. Finally, BPLP-Ser/HA putty demonstrates in vivo regeneration in a critical-sized rat calvaria model equivalent to gold standard autograft. BPLP-Ser/HA putty represents a simple, off-the-shelf solution to the combined challenges of acute wound management and subsequent bone regeneration.

Phototherapy and optical waveguides for the treatment of infection

With rapid emergence of multi-drug resistant microbes, it is imperative to seek alternative means for infection control. Optical waveguides are an auspicious delivery method for precise administration of phototherapy. Studies have shown that phototherapy is promising in fighting against a myriad of infectious pathogens (i.e. viruses, bacteria, fungi, and protozoa) including biofilm-forming species and drug-resistant strains while evading treatment resistance. When administered via optical waveguides, phototherapy can treat both superficial and deep-tissue infections while minimizing off-site effects that afflict conventional phototherapy and pharmacotherapy. Despite great therapeutic potential, exact mechanisms, materials, and fabrication designs to optimize this promising treatment option are underexplored. This review outlines principles and applications of phototherapy and optical waveguides for infection control. Research advances, challenges, and outlook regarding this delivery system are rigorously discussed in a hope to inspire future developments of optical waveguide-mediated phototherapy for the management of infection and beyond.

Comparison of sodium alginate-based and sodium hyaluronate-based submucosal injection materials based on rheological analysis

As a viscous high-performance submucosal injection material (SIM) used in endoscopic submucosal dissection (ESD), sodium alginate-based SIM (SA-SIM) was recently introduced as high-performance SIM equivalent to sodium hyaluronate-based SIM (HA-SIM) in Japan. However, a comprehensive, detailed comparison of SA and HA is yet to be performed. In this study, we precisely measured the viscoelastic properties, submucosal elevation height (SEH), and injection pressure (IP). Furthermore, we compared the outcomes of ESD using an ex vivo ESD model. There was no significant difference in SEHs between HA-SIM and SA-SIM at all post-injection times, and the IP of the SA-SIM injection was significantly higher than that of the HA-SIM injection in all conditions (P < 0.0001). The viscosity at high shear rates of SA-SIM was higher than that of HA-SIM; this result was consistent with SEH/IP measurement results. No significant difference was observed in ESD procedure time and total volume of injected SIM between HA-SIM and SA-SIM (18.1 ± 6.7 and 17.8 ± 6.0 min, P = 0.8987; 13.3 ± 5.3 and 11.6 ± 5.9 ml, P = 0.4658, respectively). Although SA-SIM was slightly more difficult to inject than HA-SIM, there was no significant difference in performance between the materials. Thus, this basic study demonstrated that SA-SIM can be used for endoscopic treatment as well as HA-SIM, and supported previous clinical research data.

An innovative next-generation endoscopic submucosal injection material with a 2-step injection system (with video)

BACKGROUND AND AIMS

Next-generation submucosal injection materials (SIMs) with higher performance and flexibility than the current SIMs (eg, 0.4% sodium hyaluronate solution [HA]) are expected to improve the outcomes of endoscopic submucosal dissection (ESD) but are difficult to develop. We developed a next-generation SIM by devising a 2-solution-type SIM comprising 2.0% calcium chloride solution (Ca) and 0.4% sodium alginate solution (SA) and evaluated its performance.

METHODS

Viscoelasticity, submucosal elevation height, and injection pressure of HA, SA, and the next-generation SIM were measured. Outcomes of ESDs on pseudo-lesions in ex vivo porcine stomach/colon models were compared.

RESULTS

The dramatic increase in SA viscoelasticity with the addition of Ca facilitated the formation of highly viscous submucosal cushions that can be controlled by endoscopists. The submucosal elevation height of the next-generation SIM was significantly higher than that of HA or SA with the same injection pressure. The ESD procedure time using the next-generation SIM was significantly shorter than that using HA or SA (14.2 ± 6.1 vs 29.2 ± 9.1 minutes, P = .0004, or 14.2 ± 6.1 vs 29.1 ± 5.9 minutes, P <.0001). Furthermore, the total injection volume for the next-generation SIM was considerably lower than that for HA or SA (7.0 ± 0.9 vs 17.2 ± 3.4 mL, P <.0001, or 7.0 ± 0.9 vs 16.2 ± 2.9 mL, P <.0001).

CONCLUSIONS

We developed an ideal next-generation SIM that achieved high performance and high flexibility in ex vivo models. Our findings warrant further investigations in a patient population.

Off-label use of 0.4 % sodium hyaluronate teardrops: a safe and effective solution for submucosal injection in gastric endoscopic submucosal dissection

Background and study aims  Submucosal (SM) injection is a critical step in endoscopic submucosal dissection (ESD). In Japan, use of viscous solutions such as sodium hyaluronate are recommended; the commercially product available is MucoUp (Seikagaku Co. and Boston Scientific Japan Co., Japan). Nevertheless, MucoUp is expensive and unavailable in many Western countries. For the past 8 years, we have been using low-cost sterile teardrops solution composed of 0.4 % sodium hyaluronate (Adaptis Fresh, Legrand Laboratory, Brazil). This solution is readily available in drugstores with a cost of approximately US$ 10.00 for each 10-cc bottle. The aim of this study was to present the clinical outcome with off-label sodium hyaluronate use for SM injection in gastric ESD. Patients and methods  A single-center retrospective study of collected data investigating consecutive patients that underwent gastric ESD between 2012 and 2019. ESD was performed using 0.4 % sodium hyaluronate teardrop for SM injection and Flush Knife BT 2.5 (Fujifilm Co., Japan). The following data were analyzed: clinical-pathological features, en-bloc, R0 and curative resection rate, procedure duration, adverse events, and clinical outcome. Results  ESD was performed with sodium hyaluronate for submucosal injection in 78 patients. The en-bloc resection rate and R0 resection rate were 96.1 % and 92.3 %, respectively. The curative resection rate for epithelial lesions was 83.8 %. Adverse events occurred in 5 cases (6.3 %): delayed bleeding (3.8 %, 3 cases) and perforation (2.5 %, 2 cases); all managed successfully by clipping and thermal coagulation. The mean volume of sodium hyaluronate solution used per patient was 10 cc (SD: ± 8 cc). During follow-up (mean: 17 months; SD: ± 14.5 months), two patients developed metachronous lesions (2.5 %). Conclusions  Off-label use of teardrops with 0.4 % sodium hyaluronate for submucosal injection was demonstrated to be safe and able to provide an effective submucosal cushion that facilitates SM dissection in gastric ESD procedures.

Cellulose nanofiber dispersion as a new submucosal injection material for endoscopic treatment: preliminary experimental study

Background and aims  Although various solutions have been tested for submucosal injections during endoscopic treatment, the ideal solution has not been established. We investigated the suitability of a cellulose nanofiber (CNF) dispersion with high viscosity and thixotropy as a potential submucosal injection material for endoscopic treatment. Methods  We evaluated the catheter injectability and mucosa-elevating capacity of CNF dispersion compared with sodium hyaluronate (SH) solution, which has been reported to be a promising submucosal injection solution. The catheter injectability of CNF dispersion was examined under conditions equivalent to those used clinically in endoscopic treatment. The mucosa-elevating capacity of CNF dispersion was examined in porcine stomachs. Results  There was no significant difference between the catheter injectability of 0.4 % CNF dispersion and 0.4 % SH solutions; however, 0.4 % CNF dispersion maintained significantly higher and longer elevation of the submucosal layer than 0.4 % SH solution. A clear separation of the mucosal layer from the underlying muscle layer was achieved by injecting 0.4 % CNF dispersion. Conclusion  This preliminary study suggests that CNF dispersion could be an ideal submucosal injection material for endoscopic treatment because of its unique high thixotropy index.

Evaluation of Eleview® Bioadhesive Properties and Cushion-Forming Ability

Submucosal injection is generally required for both endoscopic-mucosal resection (EMR) and submucosal dissection (ESD). SIC-8000 (Eleview®) is a new liquid composition in the form of a microemulsion for submucosal injection, approved by the Food and Drug Administration (FDA) 510(k) and Conformité Européene (CE) marked, containing a biocompatible polymer as a cushioning agent. The aim of this study was to evaluate Eleview®’s performance in terms of bioadhesive properties and cushion-forming ability. The bioadhesion was evaluated by measuring the interaction between Eleview® and the extracellular matrix (the main component of the submucosal layer) using the texture analyzer. To better comprehend the mechanism of action of Eleview® after submucosal injection, force of detachment and adhesion work were measured for the following formulations: Eleview®, Eleview® without poloxamer (functional polymer), poloxamer solution alone, normal saline, and MucoUp® (competing product on the Japanese market). The results obtained show the interaction between Eleview® and the extracellular matrix, highlighting the stronger bioadhesive properties of Eleview® compared with Eleview® without poloxamer, poloxamer solution alone, as well as normal saline and MucoUp®. The ability of Eleview® to form a consistent and long-lasting cushion in situ, once injected into the submucosal layer, was tested ex vivo on a porcine stomach. The results obtained show a better permanence in situ for the product compared with normal saline injection and to MucoUp® (t-test, p < 0.05).

Design of Nanocomposite Injectable Hydrogels for Minimally Invasive Surgery

Biocompatible hydrogels are materials that hold great promise in medicine and biology since the porous structure, the ability to entrap a large amount of water, and the tunability of their mechanical and tissue adhesive properties make them suitable for several applications, including wound healing, drug and cell delivery, cancer treatment, bioelectronics, and tissue regeneration. Among the possible developed systems, injectable hydrogels, owing to their properties, are optimal candidates for in vivo minimally invasive procedures. To be injectable, a hydrogel must be liquid before and during the injection, but it must quickly jellify after injection to form a soft, self-standing, solid material. The possibility to work with a liquid precursor encoding the functions that will be available after gelation allows the development of biocompatible materials that can be employed in surgery and, in particular, in noninvasive procedures. The underlying idea is to reach the target tissue by using just a needle, or by exploiting the natural body orifices, reducing surgery procedure time, induced pain, and risk of infections. Hydrogels with different properties can be obtained by changing the type of cross-linking, the cross-linking density or the molecular weight of the polymer, or by introducing pending functional groups. The introduction of a nanofiller in the hydrogel network allows for expanding the suite of the structural and functional properties and for better mimicking native tissues. In this Account, we discuss how to provide a hydrogel network with designed properties by playing with both the polymeric chains and the fillers. We present selected examples from the literature that show how to introduce stiffness, stretchability, adhesiveness, self-healing, anisotropy, antimicrobial activity, biodegradability, and conductivity in injectable hydrogels. We further describe how the chemical composition, the mechanical properties, and the microarchitecture of the hydrogel influence cell adhesion, proliferation, and differentiation. Examples of injectable hydrogels for innovative minimally invasive procedures are then discussed in detail; in particular, we showcase the use of hydrogels for tumor resection and as vascular chemoembolization agents. We further discuss how one can improve the rheological properties of injectable hydrogels to exploit them in osteochondral tissue engineering. The effect of the introduction of a conductive filler is then presented in relation to the development of electroactive scaffolds for cardiac-tissue engineering and neural and nerve repair. We believe that the rational design of biocompatible, injectable hybrid hydrogels with tunable properties will likely play a crucial role in reducing the invasiveness and improving the outcome of several clinical and surgical setups.

A New Ex Vivo Model for the Evaluation of Endoscopic Submucosal Injection Material Performance

Increasing the performance of submucosal injection materials (SIMs) is important for endoscopic therapy of early gastrointestinal cancer. It is essential to establish an ex vivo model that can evaluate SIM performance accurately, for developing high-performance SIMs. In our previous study, we developed a new ex vivo model that can be used to evaluate the performance of various SIMs in detail by applying constant tension to the specimen's ends. We also confirmed that the proposed new ex vivo model allows accurate submucosal elevation height (SEH) measurement under uniform conditions and detailed comparisons of the performances of various types of SIMs. Here, we describe the new ex vivo model and explain the detailed setup methodology of this model. Since all parts of the new model were easy to obtain, the setup of the new model could be completed quickly. SEH of various SIMs could be measured more accurately by using the new model. The critical factor that determines SIM performance can be identified using the new model. SIM development speed will drastically increase after the factor has been identified.

Identification of the critical viscoelastic factor in the performance of submucosal injection materials

High-performance submucosal injection materials (SIMs) contribute to the success of endoscopic therapy for early-stage gastrointestinal neoplasms. This study aimed to identify the most important factor (viscoelastic parameter) that determines SIM performance and the ease of injection. To determine the ideal viscoelastic parameters of SIMs, submucosal elevation heights (SEHs) and the ease of submucosal injection [characterized by injection pressures (IPs)] were evaluated using a newly developed ex vivo model, in which a constant tension was applied to the studied specimen. The strongest positive correlation was observed between the loss modulus determined at an oscillation frequency of 0.1 rad/s and SEH (correlation coefficient > 0.9) and between the loss modulus at 10 rad/s and IP (correlation coefficient > 0.9). SIMs with high loss moduli (0.1 rad/s) also contributed to maintenance of the submucosal elevation. Moreover, the SEHs of pseudoplastic fluid SIMs (whose loss moduli increased slightly with increasing angular frequency) were greater than those of Newtonian fluid SIMs (whose loss modulus increased drastically with increasing angular frequency). In this study, the ideal viscoelastic SIM parameters were clarified. The loss modulus (0.1 rad/s) was the most important viscoelastic factor affecting SIM performance. Additionally, the development of pseudoplastic fluid SIMs may lead to the creation of next-generation SIMs, with a performance superior to that of sodium hyaluronate, which is currently used widely in endoscopic treatments.

Citrate chemistry and biology for biomaterials design

Leveraging the multifunctional nature of citrate in chemistry and inspired by its important role in biological tissues, a class of highly versatile and functional citrate-based materials (CBBs) has been developed via facile and cost-effective polycondensation. CBBs exhibiting tunable mechanical properties and degradation rates, together with excellent biocompatibility and processability, have been successfully applied in vitro and in vivo for applications ranging from soft to hard tissue regeneration, as well as for nanomedicine designs. We summarize in the review, chemistry considerations for CBBs design to tune polymer properties and to introduce functionality with a focus on the most recent advances, biological functions of citrate in native tissues with the new notion of degradation products as cell modulator highlighted, and the applications of CBBs in wound healing, nanomedicine, orthopedic, cardiovascular, nerve and bladder tissue engineering. Given the expansive evidence for citrate's potential in biology and biomaterial science outlined in this review, it is expected that citrate based materials will continue to play an important role in regenerative engineering.

Rebamipide solution: a novel submucosal injection material to promote healing speed and healing quality of ulcers induced by endoscopic submucosal dissection

BACKGROUND AND AIMS

Rebamipide is administered perorally to protect the gastric mucosa. We assessed the efficacy and safety of a novel rebamipide solution as a submucosal injection material for endoscopic submucosal dissection (ESD) using an in vivo porcine model.

METHODS

An endoscopist blinded to the test agents performed ESDs of hypothetical 30 mm lesions using a 2% rebamipide solution at 2 sites (rebamipide group) and a saline solution at 2 other sites (control group) in the stomachs of 8 pigs. The technical outcomes were compared between the 2 groups. The gastric ulcer stages were evaluated by endoscopy once weekly for 4 weeks after the ESD to determine the healing score (1-6). The pigs were killed at 1 week (n = 2), 2 weeks (n = 2), and 4 weeks (n = 4) after the ESD for pathologic evaluation of ESD-induced ulcers and scarring.

RESULTS

There were no significant differences in any of the technical outcomes between the 2 groups, and no adverse events related to the ESD in any of the animals. The healing score was significantly higher in the rebamipide group than in the control group at 2 weeks (P = .027), 3 weeks (P = .034), and 4 weeks (P = .012). In the histopathologic assessment, fibrosis was significantly less extensive in the rebamipide group than in the control group at 2 weeks (P = .02) and 4 weeks (P = .04).

CONCLUSIONS

The rebamipide solution appeared to promote both the speed and quality of healing of ESD-induced ulcers by suppressing fibrosis.

Development of a new ex vivo model for evaluation of endoscopic submucosal injection materials performance

BACKGROUND AND AIMS

Development of high-performance submucosal injection materials (SIMs) contribute to the advancement of endoscopic therapy for early-stage gastrointestinal neoplasms. This study aimed to develop a new ex vivo model that mimics the human gastrointestinal tract to evaluate the performance (the height and duration of the submucosal elevation) of various SIMs in detail.

METHODS

A new ex vivo model that applies a constant tension to the tested specimen (the porcine gastric specimen) was developed. SIMs were injected into the submucosa at the center or edge of the tested specimen, and submucosal elevation heights (SEHs) were measured over time.

RESULTS

The average value and standard deviation of SEH determined using the conventional model (the tested specimen was fixed with pins) were higher than those obtained using the new model, which showed that the new model could precisely measure the SEH of a given SIM. In addition, the performance (SEH) of SIMs decreased with increasing tension applied to the specimen, suggesting that the performance of SIMs deteriorates with the over-expansion of the gastrointestinal tract. The submucosal elevation formed at the specimen edge disappeared faster than that formed at the specimen's center.

CONCLUSIONS

The proposed new ex vivo model allows accurate SEH measurement under uniform conditions and detailed comparison of the performances of various types of SIMs and can contribute to the development of high-performance materials.

Design Strategies and Applications of Biomaterials and Devices for Hernia Repair

Hernia repair is one of the most commonly performed surgical procedures worldwide, with a multi-billion dollar global market. Implant design remains a critical challenge for the successful repair and prevention of recurrent hernias, and despite significant progress, there is no ideal mesh for every surgery. This review summarizes the evolution of prostheses design toward successful hernia repair beginning with a description of the anatomy of the disease and the classifications of hernias. Next, the major milestones in implant design are discussed. Commonly encountered complications and strategies to minimize these adverse effects are described, followed by a thorough description of the implant characteristics necessary for successful repair. Finally, available implants are categorized and their advantages and limitations elucidated, including non-absorbable and absorbable (synthetic and biologically derived) prostheses, composite prostheses, and coated prostheses. This review not only summarizes the state of the art in hernia repair, but also suggests future research directions toward improved hernia repair utilizing novel materials and fabrication methods.

Gastric endoscopic submucosal dissection using sodium carboxymethylcellulose as a new injection substance

AIM

To investigate the feasibility of endoscopic submucosal dissection (ESD) using sodium carboxymethylcellulose (SCMC) for gastric cancer.

METHODS

During October 2011 through April 2013, 98 lesions from 98 patients who underwent ESD using SCMC (ESD-SCMC) for early gastric cancer were enrolled in this study.　Two endoscopists, who had each performed fewer than 30 ESD procedures (less-experienced ESD physicians), performed ESD-SCMC under the supervision of two experts.　The primary outcome was the en bloc resection rate.　Secondary outcomes included the complete resection rate, the procedural time, the bleeding rate after SCMC injection, and complications.　Patient characteristics, time necessary for hemostasis after SCMC injection, rate of treatment completion by less-experienced ESD physicians alone, and the effects of SCMC during ESD and on resected specimens were also evaluated.

RESULTS

The en bloc resection rate was 100%.　Among these resections, 87.8% of the cases were completed by a less-experienced ESD physician alone.　The complete resection rate was 98.0%.　The mean total procedural time was 75.4 min.　The mean incidence of intraoperative bleeding following SCMC local injection was 1.7 times.　No bleeding was observed after SCMC injection in 29.6% of cases (29/98).　Five complications occurred: one case of microperforation (1.0%) and four cases of postoperative bleeding (4.0%).　SCMC remained in the submucosa.　The submucosa was readily manipulated when the deep submucosa was dissected, even after placing the specimen on a slide.

CONCLUSION

ESD-SCMC is feasible for the resection of early gastric cancer.

Endoscopic submucosal dissection and its potential role in the management of early colorectal neoplasia in UK

In Europe, colorectal cancer is the most common newly diagnosed cancer and the second most common cause of cancer deaths, accounting for approximately 436 000 incident cases and 212 000 deaths in 2008. National screening programmes will increase the number of early (pT1) cancers detected. pT1 cancers are those showing invasion through the muscularis mucosae into the submucosa but not into the muscularis propria. Microstaging of pT1 cancer is crucial in predicting those cases less likely to cause nodal disease and that will be cured with endoscopic resection alone. The submucosal extent and other histological features predict the risk of nodal disease, and for this reason, en bloc resection is highly desirable. Endoscopic submucosal dissection enables en bloc resection of mucosal and submucosal disease and could reduce the need for surgery in some cases by definitive initial resection.

Solutions for submucosal injection in endoscopic resection: a systematic review and meta-analysis

BACKGROUND AND AIMS

Submucosal injection is standard practice in endoscopic mucosal resection of gastrointestinal lesions. Several solutions are used. Our aim was to systematically review their efficacy and safety.

PATIENTS AND METHODS

We performed a systematic review and meta-analysis using a random effects model of randomized controlled trials (RCTs) from MEDLINE. Studies in animal models were qualitatively assessed for efficacy and safety.

RESULTS

In total, 54 studies were qualitatively assessed. Eleven RCTs were analyzed, two of which were on endoscopic submucosal dissection (ESD). The quantitative synthesis included nine RCTs on endoscopic mucosal resection (EMR), comprising 792 subjects and 793 lesions. Mean lesion size was 20.9 mm (range 8.5 - 46 mm). A total of 209 lesions were randomized to sodium hyaluronate (SH) vs normal saline (NS), 72 to 50 % dextrose (D50) vs NS, 82 to D50 vs SH, 43 to succinylated gelatin, 25 to hydroxyethyl starch and 36 to fibrinogen. In total, 385 were randomized to NS as controls. NS and SH are the best studied solutions and seem to be equally effective in achieving complete resection (OR 1.09; 95 %CI 0.82, 1.45). No solution was proven to be superior in complete resection rate, post-polypectomy bleeding or coagulation syndrome/perforation incidence. Many solutions have been tested in animal studies and most seem more effective for mucosal elevation than NS.

CONCLUSIONS

There are several solutions in clinical use and many more under research, but most are poorly studied. SH seems to be clinically equivalent to NS. There are no significant differences in post-polypectomy complications. Larger RCTs are needed to determine any small differences that may exist between solutions.

A feasibility study of a thermally sensitive elastin-like polypeptide for submucosal injection application in endoscopic resection in 3 animal models

BACKGROUND AND AIMS

Endoscopic submucosal dissection (ESD) can successfully resect large lesions en bloc by using a submucosal injection solution, but the cost of currently available submucosal injection solutions is not satisfactory. The authors' aim was to evaluate the feasibility and effectiveness of a thermally sensitive elastin-like polypeptide (ELP) used as submucosal injection solution in ESD.

METHODS

We conducted an ex vivo study to determine the optimal concentration of ELPs in rabbits, an in vivo study to evaluate the effectiveness of mucosal elevation in rats, and a large animal study to confirm the feasibility of preclinical application by using conventional clinical procedure in pigs.

RESULTS

ELP (500 μM) was proved to be the optimal injectable submucosal injection solution and elevated mucosa more efficiently than any control. The same concentration of ELP exhibited an equivalent effectiveness of mucosal elevation, the retention of the elevation, and minimal bleeding with sodium hyaluronate. The ESD procedure time with 500 μM ELP in a preclinical study with pigs was significantly shorter than with any other concentration of ELP and normal saline solution.

CONCLUSIONS

Use of ELP as submucosal injection solution was feasible, with higher and longer-lasting elevation and fewer adverse events.

Improved Techniques for Endoscopic Mucosal Resection (EMR) in Colorectal Adenoma

Background

Endoscopic therapy of colorectal adenomas and early cancers is a standard method. Besides oncological criteria, the method is limited by polyp location, size, and texture.

Method

Based on the current literature, technical modifications and developments in endoscopic mucosal resection are described.

Results

Numerous approaches exist to improve the conditions of resection, including optimisation of mucosal elevation and modification of techniques, tools, and devices.

Conclusion

Endoscopic therapy of sessile and flat colorectal polyps remains a challenge. Some of the presented modifications can help to address this challenge.

Citrate-Based Biomaterials and Their Applications in Regenerative Engineering

Advances in biomaterials science and engineering are crucial to translating regenerative engineering, an emerging field that aims to recreate complex tissues, into clinical practice. In this regard, citrate-based biomaterials have become an important tool owing to their versatile material and biological characteristics including unique antioxidant, antimicrobial, adhesive, and fluorescent properties. This review discusses fundamental design considerations, strategies to incorporate unique functionality, and examples of how citrate-based biomaterials can be an enabling technology for regenerative engineering.

Rebamipide delivered by brushite cement enhances osteoblast and macrophage proliferation

Many of the bioactive agents capable of stimulating osseous regeneration, such as bone morphogenetic protein-2 (BMP-2) or prostaglandin E2 (PGE2), are limited by rapid degradation, a short bioactive half-life at the target site in vivo, or are prohibitively expensive to obtain in large quantities. Rebamipide, an amino acid modified hydroxylquinoline, can alter the expression of key mediators of bone anabolism, cyclo-oxygenase 2 (COX-2), BMP-2 and vascular endothelial growth factor (VEGF), in diverse cell types such as mucosal and endothelial cells or chondrocytes. The present study investigates whether Rebamipide enhances proliferation and differentiation of osteoblasts when delivered from brushite cement. The reactive oxygen species (ROS) quenching ability of Rebampide was tested in macrophages as a measure of bioactivity following drug release incubation times, up to 14 days. Rebamipide release from brushite occurs via non-fickian diffusion, with a rapid linear release of 9.70% ± 0.37% of drug per day for the first 5 days, and an average of 0.5%-1% per day thereafter for 30 days. Rebamipide slows the initial and final cement setting time by up to 3 and 1 minute, respectively, but does not significantly reduce the mechanical strength below 4% (weight percentage). Pre-osteoblast proliferation increases by 24% upon exposure to 0.4 uM Rebamipide, and by up to 73% when Rebamipide is delivered via brushite cement. Low doses of Rebamipide do not adversely affect peak alkaline phosphatase activity in differentiating pre-osteoblasts. Rebamipide weakly stimulates proliferation in macrophages at low concentrations (118 ± 7.4% at 1 uM), and quenches ROS by 40-60%. This is the first investigation of Rebamipide in osteoblasts.

Endoscopic Submucosal Dissection (ESD) in Colorectal Tumors

Background

Endoscopic submucosal dissection (ESD) – initially developed for the treatment of early gastric cancer in Japan – is an attractive option for en bloc resection of larger sessile or flat colorectal neoplasia.

Methods

A review of the current literature on colorectal ESD was carried out.

Results

In contrast to conventional endoscopic mucosal resection (EMR), ESD for larger colorectal neoplasia yields high en bloc resection rates and very low recurrence rates. The frequency of delayed bleeding is similar for EMR and ESD. Higher perforation rates during ESD are mostly due to microperforations identified and treated during the intervention, and are therefore of minor clinical relevance. A major disadvantage of ESD is the necessity for high-level endoscopic skills and long procedure times. ESD also has the potential to replace laparoscopic surgery or transanal endoscopic microsurgery mainly due to its lower complication rates.

Conclusion

ESD for the resection of larger flat or sessile colorectal lesions has potential advantages over conventional EMR or minimally invasive surgery. Due to the low incidence of early gastric cancer, experience with ESD will remain limited in Western countries. The spread of colorectal ESD will depend on adequate training opportunities and also on modifications yielding a reduction in procedure time.

New progress in endoscopic treatment of esophageal diseases

The technique of endoscopic submucosal dissection (ESD), which was developed for en bloc resection of large lesions in the stomach, has been widely accepted for the treatment of the entire gastrointestinal tract. Many minimally invasive endoscopic therapies based on ESD have been developed recently. Endoscopic submucosal excavation, submucosal tunneling endoscopic resection and laparoscopic-endoscopic cooperative surgery have been used to remove submucosal tumors, especially tumors which originate from the muscularis propria of the digestive tract. Peroral endoscopic myotomy has recently been described as a scarless and less invasive surgical myotomy option for the treatment of achalasia. Patients benefit from minimally invasive endoscopic therapy. This article, in the highlight topic series, provides detailed information on the indications and treatments for esophageal diseases.

Successful endoscopic strategies for difficult polypectomy

PURPOSE OF REVIEW

Standard endoscopic polypectomy is a powerful technique to remove most polyps found in the gastrointestinal tract. However, a small percentage of polyps can be classified as difficult, based on size, location, and/or configuration. Traditionally, these difficult polyps were referred for surgical segmental colectomy. Recently, with advancements in endoscopic techniques and accessories, a majority of these difficult polyps are now able to be completely resected using entirely endoscopic techniques.

RECENT FINDINGS

Endoscopic techniques and accessories have been evolving during recent years, including increased dissemination of techniques of endoscopic submucosal dissection to the western hemisphere. In addition to refinement of endoscopic techniques, there has been increased interest in developing improved endoscopic accessories, including novel submucosal injectate with auto-dissecting properties, to improve safety and efficiency of endoscopic resection of difficult polyps.

SUMMARY

This article will review currently available techniques and strategies for successful endoscopic resection for difficult polyps.