Self-degradation of tissue adhesive based on oxidized dextran and poly-l-lysine

Toward chronopharmaceutical drug delivery patches and biomaterial coatings for the facilitation of wound healing

Implantation of a biomaterial entails a form of injury where the integration of the implant into the host tissue greatly depends on the proper healing of the wound. Wound healing, itself, consists of a number of physiological processes, each occurring within a characteristic time window. A composite, multilayered polymeric drug delivery carrier for adhesion to the wound site and its supply with molecules released at precise time windows at which the stages in the healing process that they target occur is conceptualized here. We also present a simplified version of one such multilayered composite fabricated by a combination of solvent casting and dip coating, comprising the base poly(ε-caprolactone) layer reinforced with hydroxyapatite nanoparticles, poly(glutamic acid) mesolayer and poly-l-lysine surface layer, each loaded with specific small molecules and released at moderately distinct timescales, partially matching the chronology of wound healing. To that end, the base layer proved suitable for the delivery of an anti-inflammatory molecule or an angiogenic agent, the mesolayer appeared appropriate for the delivery of an epithelialization promoter or a granulation factor, and the adhesive surface layer interfacing directly with the site of injury showed promise as a carrier of a vasodilator. The drug release mechanisms were diffusion-driven, suggesting that the drug/carrier interaction is a key determinant of the release kinetics, as important as the nature of the polymer and its hydrolytic degradation rate in the aqueous medium. Morphological and phase composition analyses were performed, along with the cell compatibility ones, demonstrating solid adhesion and proliferation of both transformed and primary fibroblasts on both surfaces of the composite films. The design of the multilayered composite drug delivery carriers presented here is prospective, but requires further upgrades to achieve the ideal of a perfect timing of the sequential drug release kinetics and a perfect resonance with the physiological processes defining the chronology of wound healing.

Dess-Martin oxidation of hydroxypropyl and hydroxyethyl cellulose, and exploration of their polysaccharide/polypeptide hydrogels

Oxidation of polysaccharides can provide biomaterials with aldehyde and ketone functional groups, which are particularly useful in biomedical applications, like drug delivery, tissue adhesion and hydrogel preparation. However, despite their potential, only a few such methods have been reported, and achieving selective, quantitative oxidation of polysaccharides remains challenging. Herein we report utilization of a mild oxidant, Dess-Martin periodinane, for the chemoselective oxidation of hydroxypropyl cellulose (HPC) and hydroxyethyl cellulose (HEC). Our findings reveal that the oxidation of HPC is fast, efficient and achieves near-quantitative conversion. Moreover, both Ox-HPC and Ox-HEC exhibit low cell toxicity, and readily form hydrogels by reaction with a polypeptide comprising amino acids with amine-containing a-substituents, α-poly-l-lysine. The peptide/polysaccharide hydrogels display self-healing properties, injectability, and antimicrobial activity, making them highly attractive for biomedical applications including in wound dressings.

Polysaccharide-based hydrogels for medical devices, implants and tissue engineering: A review

Hydrogels are highly biocompatible biomaterials composed of crosslinked three-dimensional networks of hydrophilic polymers. Owing to their natural origin, polysaccharide-based hydrogels (PBHs) possess low toxicity, high biocompatibility and demonstrate in vivo biodegradability, making them great candidates for use in various biomedical devices, implants, and tissue engineering. In addition, many polysaccharides also show additional biological activities such as antimicrobial, anticoagulant, antioxidant, immunomodulatory, hemostatic, and anti-inflammatory, which can provide additional therapeutic benefits. The porous nature of PBHs allows for the immobilization of antibodies, aptamers, enzymes and other molecules on their surface, or within their matrix, potentiating their use in biosensor devices. Specific polysaccharides can be used to produce transparent hydrogels, which have been used widely to fabricate ocular implants. The ability of PBHs to encapsulate drugs and other actives has been utilized for making neural implants and coatings for cardiovascular devices (stents, pacemakers and venous catheters) and urinary catheters. Their high water-absorption capacity has been exploited to make superabsorbent diapers and sanitary napkins. The barrier property and mechanical strength of PBHs has been used to develop gels and films as anti-adhesive formulations for the prevention of post-operative adhesion. Finally, by virtue of their ability to mimic various body tissues, they have been explored as scaffolds and bio-inks for tissue engineering of a wide variety of organs. These applications have been described in detail, in this review.

Glycopolypeptide hydrogels with adjustable enzyme-triggered degradation: A novel proteoglycans analogue to repair articular-cartilage defects

Proteoglycans (PGs), also known as a viscous lubricant, is the main component of the cartilage extracellular matrix (ECM). The loss of PGs is accompanied by the chronic degeneration of cartilage tissue, which is an irreversible degeneration process that eventually develops into osteoarthritis (OA). Unfortunately, there is still no substitute for PGs in clinical treatments. Herein, we propose a new PGs analogue. The Glycopolypeptide hydrogels in the experimental groups with different concentrations were prepared by Schiff base reaction (Gel-1, Gel-2, Gel-3, Gel-4, Gel-5 and Gel-6). They have good biocompatibility and adjustable enzyme-triggered degradability. The hydrogels have a loose and porous structure suitable for the proliferation, adhesion, and migration of chondrocytes, good anti-swelling, and reduce the reactive oxygen species (ROS) in chondrocytes. In vitro experiments confirmed that the glycopolypeptide hydrogels significantly promoted ECM deposition and up-regulated the expression of cartilage-specific genes, such as type-II collagen, aggrecan, and glycosaminoglycans (sGAG). In vivo, the New Zealand rabbit knee articular cartilage defect model was established and the hydrogels were implanted to repair it, the results showed good cartilage regeneration potential. It is worth noting that the Gel-3 group, with a pore size of 122 ​± ​12 ​μm, was particularly prominent in the above experiments, and provides a theoretical reference for the design of cartilage-tissue regeneration materials in the future.

Novel external reinforcement device for gastrointestinal anastomosis in an experimental study

BACKGROUND

Anastomotic leakage has been reported to occur when the load on the anastomotic site exceeds the resistance created by sutures, staples, and early scars. It may be possible to avoid anastomotic leakage by covering and reinforcing the anastomotic site with a biocompatible material. The aim of this study was to evaluate the safety and feasibility of a novel external reinforcement device for gastrointestinal anastomosis in an experimental model.

METHODS

A single pig was used in this non-survival study, and end-to-end anastomoses were created in six small bowel loops by a single-stapling technique using a circular stapler. Three of the six anastomoses were covered with a novel external reinforcement device. Air was injected, a pressure test of each anastomosis was performed, and the bursting pressure was measured.

RESULTS

Reinforcement of the anastomotic site with the device was successfully performed in all anastomoses. The bursting pressure was 76.1 ± 5.7 mmHg in the control group, and 126.8 ± 6.8 mmHg in the device group, respectively. The bursting pressure in the device group was significantly higher than that in the control group (p = 0.0006).

CONCLUSIONS

The novel external reinforcement device was safe and feasible for reinforcing the anastomoses in the experimental model.

New Methacrylated Biopolymer-Based Hydrogels as Localized Drug Delivery Systems in Skin Cancer Therapy

The aim of the present work was to obtain drug-loaded hydrogels based on combinations of dextran, chitosan/gelatin/xanthan, and poly (acrylamide) as a sustained and controlled release vehicle of Doxorubicin, a drug used in skin cancer therapy that is associated with severe side effects. Hydrogels for use as 3D hydrophilic networks with good manipulation characteristics were produced using methacrylated biopolymer derivatives and the methacrylate group's polymerization with synthetic monomers in the presence of a photo-initiator, under UV light stimulation (365 nm). Transformed infrared spectroscopy analysis (FT-IR) confirmed the hydrogels' network structure (natural-synthetic composition and photocrosslinking), while scanning electron microscopy (SEM) analysis confirmed the microporous morphology. The hydrogels are swellable in simulated biological fluids and the material's morphology regulates the swelling properties: the maximum swelling degree was obtained for dextran-chitosan-based hydrogels because of their higher porosity and pore distribution. The hydrogels are bioadhesive on a biological simulating membrane, and values for the force of detachment and work of adhesion are recommended for applications on skin tissue. The Doxorubicin was loaded into the hydrogels and the drug was released by diffusion for all the resulting hydrogels, with small contributions from the hydrogel networks' relaxation. Doxorubicin-loaded hydrogels are efficient on keratinocytes tumor cells, the sustained released drug interrupting the cells' division and inducing cell apoptosis; we recommend the obtained materials for the topical treatment of cutaneous squamous cell carcinoma.

Biological activities and applications of exopolysaccharides produced by lactic acid bacteria: a mini-review

Exopolysaccharides (EPSs) are naturally occurring high-molecular-weight carbohydrates that have been widely studied for their biological activities, including antioxidant, immunomodulatory, anticancer and gut microbiota regulation activities. Polysaccharides are abundant in nature and can be derived from animals, plants, algae, and microorganisms, but among polysaccharides with potential uses, EPSs from microorganisms have the advantages of a short production cycle, high yield, and independence of production from season and climate and thus have broad prospects. While the safety of the producing microorganism can represent a problem in application of microbial EPSs, lactic acid bacteria (LAB) have been used by humans for thousands of years, and they and their products are generally recognized as safe. This makes LAB excellent sources for exopolysaccharides. EPS-producing LAB are readily found in nature. Through screening of strains, optimization of culture conditions, and improvement of the growth medium, the yield of EPSs from LAB can be increased and the scope of application broadened. This review summarizes EPSs from LAB in terms of structure, function and applications, as well as yield optimization, and introduces recent research on the biological activities and practical applications of LAB EPSs, aiming to provide references for researchers in related areas.

Construction of a cellulose-based high-performance adhesive with a crosslinking structure bridged by Schiff base and ureido groups

Biomass-based adhesives are considered to be the preferred alternative to formaldehyde-type wood adhesives due to their wide range of sources, low cost, and sustainability. Herein, an environmentally friendly Schiff base cross-linked compact three-dimensional network structure bio-adhesive (DAC-PEI-U) derived from polyethyleneimine (PEI), urea, and cellulose was successfully prepared, verifying by detailed FTIR, NMR, and XPS analysis. Schiff base bridging between aldehyde groups in dialdehyde cellulose (DAC) and amino groups in polyurea (PEIU) not only constructed crosslinking networks but also endowed adhesives with good adhesion property. The dry bond strength of DAC-PEI-U adhesive reached 2.71 MPa, and the wet shear strength was 1.51 MPa (hot water) and 1.34 MPa (boiling water), respectively. It not only improves the water resistance and bonding process, but also displays simple synthesis and low cost. The improved performance of DAC-PEI-U adhesive is attributed to the generation of hyperbranched cross-linking structure in the adhesive system, which results in increased cross-linking density and promotes the formation of dense cross-sections in the curing adhesive. This work paves a solid way for developing cellulose-based wood adhesives with wet bonding properties, thus holding great potential as an alternative to formaldehyde-type adhesives in wood-based panel and indoor panel bonding industries.

Elucidating the degradation mechanism of a self-degradable dextran-based medical adhesive

We developed a self-degradable medical adhesive, LYDEX, consisting of periodate-oxidized aldehyde-functionalized dextran (AD) and succinic anhydride-treated ε-poly-l-lysine (SAPL). After gelation and adhesion of LYDEX by Schiff base bond formation between the AD aldehyde groups and SAPL amino groups, molecular degradation associated with the Maillard reaction is initiated, but the detailed degradation mechanism remains unknown. Herein, we elucidated the degradation mechanism of LYDEX by analyzing the main degradation products under typical solution conditions in vitro. The degradation of the LYDEX gel with a sodium periodate/dextran content of 2.5/20 was observed using gel permeation chromatography and infrared and ¹H NMR spectroscopy. The AD ratio in the AD-SAPL mixture increased as the molecular weight decreased with the degradation time. This discovery of LYDEX self-degradability is useful for clarifying other polysaccharide hydrogel degradation mechanisms, and valuable for the use of LYDEX in medical applications, such as hemostatic or sealant materials.

Self-healing polysaccharide-based injectable hydrogels with antibacterial activity for wound healing

Because the wound is difficult to heal, repeated bacterial infection will lead to complex clinical problems. Therefore, it is necessary to find an effective method to strengthen the healing process and resist bacterial infection. Hydrogels have many advantages, such as injectability and self-healing under physiological conditions, so they have been widely studied in recent years. Hydrogels can keep the wound moist and promote the wound healing. In addition, the growth of bacteria can be obviously inhibited by hydrogels themself or by doping some antibacterial active substances. Based on this, herein, this review highlighted the preparation and properties of different polysaccharide-based injectable hydrogels, and discuss their biological applications in antibacterial therapy for wound healing in recent years.

Injectable double network hydrogel with hemostasis and antibacterial activity for promoting multidrug−resistant bacteria infected wound healing

Multidrug−resistant bacteria infections frequently occur in wound care due to the excessive use of antibiotics. It can cause scars formation, wound closure delaying, multiple organ failure, and high mortality. Here,...

Emerging Biopolymer-Based Bioadhesives

Bioadhesives have been widely used in healthcare and biomedical applications due to their ease-of-operation for wound closure and repair compared to conventional suturing and stapling. However, several challenges remain for developing ideal bioadhesives, such as unsatisfied mechanical properties, non-tunable biodegradability, and limited biological functions. Considering these concerns, naturally derived biopolymers have been considered good candidates for making bioadhesives owing to their ready availability, facile modification, tunable mechanical properties, and desired biocompatibility and biodegradability. Over the past several years, remarkable progress has been made on biopolymer-based adhesives, covering topics from novel materials designs and advanced processing to clinical translation. The developed bioadhesives have been applied for diverse applications, including tissue adhesion, hemostasis, antimicrobial, wound repair/tissue regeneration, and skin-interfaced bioelectronics. Here in this comprehensive review, recent progress on biopolymer-based bioadhesives is summarized with focuses on clinical translations and multifunctional bioadhesives. Furthermore, challenges and opportunities such as weak adhesion strength at the hydrated state, mechanical mismatch with tissues, and unfavorable immune responses are discussed with an aim to facilitate the future development of high-performance biopolymer-based bioadhesives.

A paintable ophthalmic adhesive with customizable properties based on symmetrical/asymmetrical cross-linking

In situ and efficient incision sealing for ophthalmic surgery remains unresolved. Current commercially available gel adhesives often suffer from unsuitable gelation time, difficulty in micro-delivery, and mismatched degradation period, leading to difficulties for application in ocular tissue areas. Herein, a novel hydrogel adhesive was developed based on the simultaneous crosslinking of poly(lysine) (PLL) and lysine (Lys) with an end-modified active ester multi-arm polyethylene glycol (PEG) via the amidation reaction, where the residual terminal active ester of PEG can also bond to amino groups on tissue to provide strong adhesion. Due to the different molecular structures around their amino groups, PLL and Lys can crosslink with 4-arm-PEG-NHS (active ester) respectively, to form symmetrical and asymmetrical crosslinking networks, which exhibit various mechanical properties. Therefore, just by adjusting PLL/Lys ratios, the PEG-PLL-Lys hydrogel can easily possess a suitable gelation time, appropriate mechanical properties and matched degradation rate. As a result, a paintable, readily accessible and biocompatible ophthalmic tissue adhesive (sealant) is prepared for sealing ocular tissue incision. Considering the simple strategy and outstanding performance, the PEG-PLL-Lys hydrogel is promising for clinical transformation.

A multifunctional shape-adaptive and biodegradable hydrogel with hemorrhage control and broad-spectrum antimicrobial activity for wound healing

Hemorrhage is the leading cause of preventable death of injured military and civilian patients, and subsequent infection risks endanger their lives or impede the healing of their wounds. Here, we report an injectable biodegradable hydrogel with hemostatic, antimicrobial, and healing-promoting properties. The hydrogel was prepared by dynamic cross-linking of a natural polysaccharide (dextran) with antimicrobial peptide ε-poly-l-lysine (EPL) and encapsulating base fibroblast growth factor (bFGF). The amino groups of EPL were allowed to react with the aldehyde of oxidized dextran (OD) through the Schiff-base reaction for the generation of hydrogels that have fast self-healing and injectable characteristics and adapt to the shapes of wounds. The prepared OD/EPL hydrogels promoted blood clotting in vitro and stopped bleeding in a rat liver injury model within 6 min through their platelet-aggregating ability and sealing effect. These hydrogels exhibited inherent antimicrobial effects without the use of antibiotics and effectively killed a broad spectrum of pathogenic microbes, including Gram-positive methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative Escherichia coli, and Pseudomonas aeruginosa and fungus Candida albicans in vitro. Moreover, these OD/EPL hydrogels were compatible with mammalian cells in vitro and in vivo and biodegradable in the mouse body. The loaded bFGF can be released sustainably, and it can promote angiogenesis, endothelial cell migration, and consequently accelerate the healing of wounds. The OD/EPL hydrogel inhibited MRSA infection in a rat full-thickness skin wound model and promoted healing. This kind of multifunctional hydrogel is a promising wound dressing for the emergency treatment of acute deep or penetrating injuries.

A comprehensive review on α-D-Glucans: Structural and functional diversity, derivatization and bioapplications

Glucans are the most abundant natural polysaccharides across the living kingdom with tremendous biological activities. Now a days, α-D-glucans are gaining importance as a prebiotics, nutraceuticals, immunostimulants, antiproliferative agents and biodegradable polymers in pharmaceutical and cosmetic sectors. A wide variety of bioresources including bacteria, fungi, lichens, algae, plants and animals produce α-D-glucans either as an exopolysaccharide (EPS) or a cell wall component or an energy storage polymer. The α-D-glucans exhibit great structural and functional diversity as the type of linkage and percentage of branching dictate the functional properties of glucans. Among the different linkages, bioactivities are greatly confined to the α-D-(1 → 3) linkages whereas starch and other polymers consisting of α-D-(1 → 4) (1 → 6) linkages are specific for food and pharmaceutical applications. However, the bioactivities of the α-D-(1 → 3) glucans in native form is limited mainly due to their hydrophobic nature. Hence several derivatization techniques have been developed to improve the bioavailability as well as bioactive features such as antiviral, antimicrobial, anti-inflammatory, antioxidant, immunomodulatory and antitumor properties. Though, several reports have presented about α-D-glucans, still there is an ambiguity in terms of their structure among different natural sources and moreover no comprehensive information was available on their derivatization techniques and application potential. Therefore, the present review summarizes distinct description on diverse sources, type of linkages, derivatization techniques as well as the application potential of the native and modified α-D-glucans.

Contributions of exopolysaccharides from lactic acid bacteria as biotechnological tools in food, pharmaceutical, and medical applications

Exopolysaccharides (EPS) are important bioproducts produced by some genera of lactic acid bacteria. EPS are famous for their shelf-life improving properties, techno-functional enhancing abilities in food and dairy industries, besides their beneficial health effects. Furthermore, exopolysaccharides have many prospective and well-established contributions in the field of drugs and diagnostic industry. In this review, classification of EPS produced by LAB was presented. Moreover, current and potential applications of EPS in food, dairy, baking industries, cereal-based, and functional products were described. Also, some clinical and pharmaceutical applications of EPS such as intelligent drug delivery systems (microsystems and nanosystems for sustained delivery), interpenetrating polymer networks (IPNs), anticancer drug-targeting, recombinant macromolecular biopharmaceuticals, gene delivery, tissue engineering, and role of EPS in diagnostics were highlighted. Finally, future prospects concerning enhancing EPS production, minimizing costs of their production, and exploring their contribution in further applications were discussed.

An antimicrobial peptide-immobilized nanofiber mat with superior performances than the commercial silver-containing dressing

Silver-containing dressings are widely used for the treatment of infected wounds in clinics, but the potential risks of heavy metals are still a common concern. In this study, we prepared a type of electrospun starch nanofiber mat containing the antimicrobial peptide ε-poly-lysine (Starch-EPL) and compared its relevant properties with a representative silver-containing dressing 3M™ Tegaderm™ Alginate Ag (Alginate-Ag). SEM, FTIR and EDAX results show the two samples have similar fiber structures and are loaded with antibacterial agents. The comparison results indicate that the Starch-EPL nanofiber mat has equivalent permeability and absorbency with Alginate-Ag but higher mechanical property and wettability. Moreover, the Starch-EPL nanofiber mat has comparable antibacterial activity against both Gram-negative and Gram-positive bacteria with Alginate-Ag, but markedly better biocompatibility than that. The Starch-EPL nanofiber mat can inhibit the growth of bacteria for at least 14 days by sustainably releasing EPL, showing great potential as a long-term antibacterial dressing. All these results demonstrate that the Starch-EPL nanofiber mat may be a good candidate to replace the traditional silver-containing dressings.

Efficacy of a novel self-assembling peptide hemostatic gel as rescue therapy for refractory acute gastrointestinal bleeding

BACKGROUND

Acute gastrointestinal bleeding (AGIB) results in significant morbidity and mortality. Topical hemostatic products have been developed for endoscopic use to help in the management of difficult bleeding. Our aim was to demonstrate the ease of use, safety, and efficacy of PuraStat, a novel hemostat, to control AGIB.

METHODS

We describe 77 patients (41 men) who were treated for acute upper and lower AGIB in a 2-year period. In 50 patients, bleeding occurred as a complication of a previous endoscopic procedure, predominantly endoscopic mucosal resection (EMR) and endoscopic retrograde cholangiopancreatography (ERCP); however, in the other 27 patients, it derived from peptic ulcers, angiodysplasia, cancers, and surgical anastomoses. Bleeding was spurting in 13 of the 77 patients and oozing in 64. PuraStat was used after the failure of at least two conventional hemostatic methods.

RESULTS

A mean of 2.6 conventional hemostatic methods had been attempted prior to the application of PuraStat. PuraStat achieved successful hemostasis in 90.9 % of patients. In 41 patients, once hemostasis was obtained with PuraStat, endoscopists further stabilized hemostasis by using at least one additional method. Recurrence of bleeding was observed in eight patients (10.4 %). In 16 patients with intraprocedural bleeding, it was possible to complete the procedures (14 EMR, 2 ERCP) after PuraStat hemostasis. No adverse events related to PuraStat were recorded.

CONCLUSIONS

PuraStat is feasible, safe, and effective in controlling different types of gastrointestinal hemorrhage after failure of conventional hemostatic methods. Its application also does not hinder continuing endotherapy.

Surgical applications of intracorporal tissue adhesive agents: current evidence and future development

Introduction: Traditional mechanical closure techniques pose many challenges including the risk of infection, tissue reaction, and injury to both patients and clinicians. There is an urgent need to develop tissue adhesive agents to reform closure technique. This review examined a variety of tissue adhesive agents available in the market in an attempt to gain a better understanding of intracorporal tissue adhesive agents as medical devices.Areas covered: Fundamental principles and clinical determinants of the tissue adhesives were summarized. The available tissue adhesives for intracorporal use and their relevant clinical evidence were then presented. Lastly, the perspective of future development for intracorporal tissue adhesive were discussed. Clinical evidence shows current agents are efficacious as adjunctive measures to mechanical closure and these agents have been trialed outside of clinical indications with varied results.Expert opinion: Despite some advancements in the development of tissue adhesives, there is still a demand to develop novel technologies in order to address unmet clinical needs, including low tensile strength in wet conditions, non-controllable polimerization and sub-optimal biocompatibility. Research trends focus on producing novel adhesive agents to remit these challenges. Examples include the development of biomimetic adhesives, externally activated adhesives, and multiple crosslinking strategies. Economic feasibility and biosafety are limiting factors for clinical implementation.

Controlling the degradation of cellulose scaffolds with Malaprade oxidation for tissue engineering

Cellulose scaffolds, whose biodegradation can be controlled through the reaction with amine compounds in the human body, were developed for tissue engineering applications.

Poly-l-lysine-based tissue embedding compatible with matrix-assisted laser desorption ionization-mass spectrometry imaging analysis of dry and fragile aristolochia plants

The integrity of tissue is crucial for a high-quality analysis of matrix-assisted laser desorption ionization-mass spectrometry image (MALDI-MSI). Various embedding media utilized in traditional tissue-sectioning techniques are generally not recommended for MALDI-MSI of dry and fragile plant tissues because of the ion suppression effect in MALDI ionization in the low-mass region as well as the undesirable structural deformation during the sample preparation. In this work, a novel poly-L-lysine (PLL)-based tissue embedding method was developed for MALDI-MSI analysis of dry and fragile aristolochia plant (AP) tissues. The practical application in fixation, embedding, cryosectioning, and mounting of the dry and fragile AP tissues demonstrated that the PLL-based embedding technique could provide good rigidity to the plant tissues analysis compared to that without embedding and gelatin embedding. With the assistance of the PLL embedding medium, high spatial resolution molecular ion maps of main compounds, including aristolochic acids I (AAI) and aristolochic acids II (AAII) in AP root tissue, could be achieved by MALDI-MSI with enhanced signal intensities and no obvious background interference. This work provides an alternative approach for embedding the dry and fragile plant tissues comparable with MALDI-MSI analysis.

Efficacy of a novel endoscopically deliverable muco-adhesive hemostatic powder in an acute gastric bleeding porcine model

This study investigated the effectiveness of new hemostatic adhesive powder (UI-EWD) in a swine mode of acute gastric bleeding. Gastric ulcer bleeding was induced endoscopically at two locations in each of eight heparinized mini-pigs. UI-EWD and saline were sprayed endoscopically in the experimental (n = 5) and control groups (n = 3), respectively. The hemostatic effect and hydrogel persistence on ulcers were periodically evaluated endoscopically. Initial hemostasis was achieved successfully in all lesions in the experimental group. Follow-up endoscopy showed minor delayed bleeding in 10% at 6 hours in the experimental group, whereas re-bleeding was observed in 50% at 6 hours in the control group. UI-EWD gel persisted at 90%, 80%, and 50% of ulcer bases at 6, 18, and 42 hours post-application, respectively. This study suggests that muco-adhesive UI-EWD may be effective in the endoscopic treatment of active ulcer bleeding.

Injectable hydrogels based on the hyaluronic acid and poly (γ-glutamic acid) for controlled protein delivery

Injectable hydrogels have great potential in minimally invasive delivery. In this work, novel injectable hydrogels were prepared via self-crosslinking of aldehyde hyaluronic acid (HA-CHO) and hydrazide-modified poly (γ-glutamic acid) (γ-PGA-ADH) for proteins delivery. The HA/γ-PGA hydrogels could be formed in situ as fast as 9s with high swelling ratios. Rheological properties illustrated a wide processing range and good mechanical properties, which were reflected by broad linear viscoelastic region and higher threshold shear stress (σ_c) and storage modulus (G'). Meanwhile, the gelation time, swelling ratio, rheological properties, as well as the protein release behavior could be modulated conveniently. Bovine serum albumin (BSA) was designed as a model drug to study the release behavior. We found that the release mechanisms were either diffusion or Case-II relaxation depending on the different hydrogel components. The HA/γ-PGA hydrogels also showed good biocompatibility. Therefore, the HA/γ-PGA hydrogels have great potential as promising injectable biomaterials for controlled protein delivery.

Dual Regulations of Thermosensitive Heparin-Poloxamer Hydrogel Using ε-Polylysine: Bioadhesivity and Controlled KGF Release for Enhancing Wound Healing of Endometrial Injury

Hydrogel was not only used as an effective support matrix to prevent intrauterine adhesion after endometrial injury but also served as scaffold to sustain release of some therapeutics, especially growth factor. However, because of the rapid turnover of the endometrial mucus, the poor retention and bad absorption of therapeutic agents in damaged endometrial cavity were two important factors hindering their pharmacologic effect. Herein, a mucoadhesive hydrogel was described by using heparin-modified poloxamer (HP) as the matrix material and ε-polylysine (EPL) as functional excipient. Various EPL-HP hydrogels formulations are screened by rheological evaluation and mucoadhesion studies. It was found that the rheological and mucoadhesive properties of EPL-HP hydrogels were easily controlled by changing the amount of EPL in formulation. The storage modulus of EPL-HP hydrogel with 90 μg/mL of EPL (EPL-HP-90) was elevated to be 1.9 × 10⁵ Pa, in accordance with the adhesion force rising to 3.18 N (10-fold higher than HP hydrogels). Moreover, in vitro release of model drug keratinocyte growth factor (KGF) from EPL-HP hydrogel was significantly accelerated by adding EPL in comparison with HP hydrogel. Both strong mucoadhesive ability and the accelerated drug release behavior for EPL-HP-90 made more of the encapsulated KGF absorbed by the uterus basal layer and endometrial glands after 8 h of administration in uterus cavity. Meanwhile, the morphology of endometrium in the injured uterus was repaired well after 3 d of treatment with KGF-EPL-HP-90 hydrogels. Compared with KGF-HP group, not only proliferation of endometrial epithelial cell and glands but also angiogenesis in the regenerated endometrium was obviously enhanced after treatment with KGF-EPL-HP-90 hydrogels. Alternatively, the cellular apoptosis in the damaged endometrium was significantly inhibited after treatment with KGF-EPL-HP-90 hydrogels. Overall, the mucoadhesive EPL-HP hydrogel with a suitable KGF release profile may be a more promising approach than HP hydrogel alone to repair the injured endometrium.

Enhanced sealing strength of a hydrophobically-modified Alaska pollock gelatin-based sealant

A novel tissue sealant composed of hydrophobically-modified Alaska pollock gelatin and polyethylene glycol-based crosslinker showed higher sealing effect than commercially available tissue sealant.

Design and development of polysaccharide hemostatic materials and their hemostatic mechanism

The formation of stable blood clots or hemostasis is essential to prevent major blood loss and death from excessive bleeding.

Probiotic-loaded microcapsule system for human in situ folate production: Encapsulation and system validation

This study focused on the use of a new system, an alginate|Ɛ-poly-l-lysine|alginate|chitosan microcapsule (APACM), able to immobilize a folate-producing probiotic, Lactococcus lactis ssp. cremoris (LLC), which provides a new approach to the utilization of capsules and probiotics for in situ production of vitamins. LLC is able to produce 95.25±26μg·L^-1 of folate, during 10h, and was encapsulated in the APACM. APACM proved its capacity to protect LLC against the harsh conditions of a simulated digestion maintaining a viable concentration of 6logCFU·mL^-1of LLC. A nutrients exchange capacity test, was performed using Lactobacillus plantarum UM7, a high lactic acid producer was used here to avoid false negative results. The production and release of 2g·L^-1 of lactic acid was achieved through encapsulation of L. plantarum, after 20h. The adhesion of APACM to epithelial cells was also quantified, yielding 38% and 33% of capsules adhered to HT-29 cells and Caco-2 cells, respectively.

Injectable in situ forming poly(l-glutamic acid) hydrogels for cartilage tissue engineering

Injectable, in situ forming hydrogels have exhibited many advantages in regenerative medicine. Herein, we present the novel design of poly(l-glutamic acid) injectable hydrogels via the self-crosslinking of adipic dihydrazide (ADH)-modified poly(l-glutamic acid) (PLGA-ADH) and aldehyde-modified poly(l-glutamic acid) (PLGA-CHO), and investigate their potential in cartilage tissue engineering. Both the hydrazide modification degree of PLGA-ADH and oxidation degree of PLGA-CHO can be adjusted by the amount of activators and sodium periodate, respectively. Experiments reveal that the solid content of the hydrogels, -NH₂/-CHO molar ratio, and oxidation degree of PLGA-CHO have a great effect on the gelation time, equilibrium swelling, mechanical properties, microscopic morphology, and in vitro degradation of the hydrogels. Encapsulation of rabbit chondrocytes within the hydrogels showed viability of the entrapped cells and cytocompatibility of the injectable hydrogels. A preliminary study exhibits injectability and rapid in vivo gel formation, as well as mechanical stability, cell ingrowth, and ectopic cartilage formation. These results suggest that the PLGA hydrogel has potential as an injectable cell delivery carrier for cartilage regeneration and could serve as a new biomaterial for tissue engineering.

Present and future medical applications of microbial exopolysaccharides

Microbial exopolysaccharides (EPS) have found outstanding medical applications since the mid-20th century, with the first clinical trials on dextran solutions as plasma expanders. Other EPS entered medicine firstly as conventional pharmaceutical excipients (e.g., xanthan - as suspension stabilizer, or pullulan - in capsules and oral care products). Polysaccharides, initially obtained from plant or animal sources, became easily available for a wide range of applications, especially when they were commercially produced by microbial fermentation. Alginates are used as anti-reflux, dental impressions, or as matrix for tablets. Hyaluronic acid and derivatives are used in surgery, arthritis treatment, or wound healing. Bacterial cellulose is applied in wound dressings or scaffolds for tissue engineering. The development of drug controlled-release systems and of micro- and nanoparticulated ones, has opened a new era of medical applications for biopolymers. EPS and their derivatives are well-suited potentially non-toxic, biodegradable drug carriers. Such systems concern rating and targeting of controlled release. Their large area of applications is explained by the available manifold series of derivatives, whose useful properties can be thereby controlled. From matrix inclusion to conjugates, different systems have been designed to solubilize, and to assure stable transport in the body, target accumulation and variable rate-release of a drug substance. From controlled drug delivery, EPS potential applications expanded to vaccine adjuvants and diagnostic imaging systems. Other potential applications are related to the bioactive (immunomodulator, antitumor, antiviral) characteristics of EPS. The numerous potential applications still wait to be developed into commercial pharmaceuticals and medical devices. Based on previous and recent results in important medical-pharmaceutical domains, one can undoubtedly state that EPS medical applications have a broad future ahead.

Injectable in situ self-cross-linking hydrogels based on poly(L-glutamic acid) and alginate for cartilage tissue engineering

Injectable hydrogels as an important biomaterial class have been widely used in regenerative medicine. A series of injectable poly(l-glutamic acid)/alginate (PLGA/ALG) hydrogels were fabricated by self-cross-linking of hydrazide-modified poly(l-glutamic acid) (PLGA-ADH) and aldehyde-modified alginate (ALG-CHO). Both the degree of PLGA modification and the oxidation degree of ALG-CHO could be adjusted by the amount of activators and sodium periodate, respectively. The effect of the solid content of the hydrogels and oxidation degree of ALG-CHO on the gelation time, equilibrium swelling, mechanical properties, microscopic morphology, and in vitro degradation of the hydrogels was examined. Encapsulation of rabbit chondrocytes within hydrogels showed viability of the entrapped cells and good biocompatibility of the injectable hydrogels. A preliminary study exhibited injectability and rapid in vivo gel formation, as well as mechanical stability, cell ingrowth, and ectopic cartilage formation. The injectable PLGA/ALG hydrogels demonstrated attractive properties for future application in a variety of pharmaceutical delivery and tissue engineering, especially in cartilage tissue engineering.