Experimental Study on Rats with Critical-Size Bone Defects Comparing Effects of Autologous Bone Graft, Equine Bone Substitute Bio-Gen® Alone or in Association with Platelet-Rich Fibrin (PRF).

BACKGROUND: A critical-sized bone defect (CsBD) is considered one that will not heal spontaneously and requires reconstruction. This study aims to compare the results of using different bone reconstructive techniques and to study the potential of platelet-rich fibrin (PRF) to enhance the healing properties of a bone substitute (BS). METHODS: In this experimental study on rats, the treatment of critical-sized bone defects was carried out by analysing four groups: a control group in which the bone defect was left empty; a group treated with Bio-Gen®; another group in which the defect was treated with PRF in combination with Bio-Gen®; and the last that was treated with autologous bone graft (ABG). The defects were evaluated by microcomputed tomography (µCT) and then histomorphometrically. RESULTS: From both the histological and imagistic point of view, the best results were registered in the ABG group, followed by the group treated with Bio-Gen® with PRF, Bio-Gen® group, and control group, with statistically significant differences. CONCLUSIONS: A 5 mm defect in the rat radius can be considered critical. ABG showed the best results in treating the bone defect. PRF significantly enhanced the efficacy of Bio-Gen®.

Advanced PEG-tyramine biomaterial ink for precision engineering of perfusable and flexible small-diameter vascular constructs via coaxial printing.

Vascularization is crucial for providing nutrients and oxygen to cells while removing waste. Despite advances in 3D-bioprinting, the fabrication of structures with void spaces and channels remains challenging. This study presents a novel approach to create robust yet flexible and permeable small (600-1300 µm) artificial vessels in a single processing step using 3D coaxial extrusion printing of a biomaterial ink, based on tyramine-modified polyethylene glycol (PEG-Tyr). We combined the gelatin biocompatibility/activity, robustness of PEG-Tyr and alginate with the shear-thinning properties of methylcellulose (MC) in a new biomaterial ink for the fabrication of bioinspired vessels. Chemical characterization using NMR and FTIR spectroscopy confirmed the successful modification of PEG with Tyr and rheological characterization indicated that the addition of PEG-Tyr decreased the viscosity of the ink. Enzyme-mediated crosslinking of PEG-Tyr allowed the formation of covalent crosslinks within the hydrogel chains, ensuring its stability. PEG-Tyr units improved the mechanical properties of the material, resulting in stretchable and elastic constructs without compromising cell viability and adhesion. The printed vessel structures displayed uniform wall thickness, shape retention, improved elasticity, permeability, and colonization by endothelial-derived - EA.hy926 cells. The chorioallantoic membrane (CAM) and in vivo assays demonstrated the hydrogel's ability to support neoangiogenesis. The hydrogel material with PEG-Tyr modification holds promise for vascular tissue engineering applications, providing a flexible, biocompatible, and functional platform for the fabrication of vascular structures.

Bioactive Composite Cryogels Based on Poly (Vinyl Alcohol) and a Polymacrolactone as Tissue Engineering Scaffolds: In Vitro and In Vivo Studies.

In light of the increasing resistance of pathogenic microorganisms to the action of antibiotics, essential oils extracted from plants with therapeutic activity provide a significant alternative to obtaining dressings for the treatment of skin wounds. The encapsulation of essential oils in an amphiphilic gel network allows better dispersion and preservation of hydrophobic bioactive substances while promoting their prolonged release. In this study, we focused on the development of a poly (vinyl alcohol) (PVA)/poly (ethylene brassylate-co-squaric acid) (PEBSA) platform embedded with thymol (Thy), and α-tocopherol (α-Tcp) as a co-drug structure with prospective use for the treatment and healing of skin wounds. The new complex bioactive system was prepared through repeated freeze-thaw processes. The influence of the composition on surface topography, hydrophilic/hydrophobic character, and in vitro interaction with simulated body fluids was evidenced. BALB/3T3 fibroblast cell culture demonstrated the cryogel scaffolds' cytocompatibility. Tests on Wistar rats confirmed their biocompatibility, integration with host tissue, and the absence of inflammatory processes. The bioactive compound significantly enhanced the healing process of full-thickness excision wounds in a rat model. Further investigations on in vivo infection models would assess the potential of the PVA/PEBSA platform with dual bioactive activity for clinical antimicrobial and wound healing therapy.

Modern Approaches in Wounds Management.

Wound management represents a well-known continuous challenge and concern of the global healthcare systems worldwide. The challenge is on the one hand related to the accurate diagnosis, and on the other hand to establishing an effective treatment plan and choosing appropriate wound care products in order to maximize the healing outcome and minimize the financial cost. The market of wound dressings is a dynamic field which grows and evolves continuously as a result of extensive research on developing versatile formulations with innovative properties. Hydrogels are one of the most attractive wound care products which, in many aspects, are considered ideal for wound treatment and are widely exploited for extension of their advantages in healing process. Smart hydrogels (SHs) offer the opportunities of the modulation physico-chemical properties of hydrogels in response to external stimuli (light, pressure, pH variations, magnetic/electric field, etc.) in order to achieve innovative behavior of their three-dimensional matrix (gel-sol transitions, self-healing and self-adapting abilities, controlled release of drugs). The SHs response to different triggers depends on their composition, cross-linking method, and manufacturing process approach. Both native or functionalized natural and synthetic polymers may be used to develop stimuli-responsive matrices, while the mandatory characteristics of hydrogels (biocompatibility, water permeability, bioadhesion) are preserved. In this review, we briefly present the physiopathology and healing mechanisms of chronic wounds, as well as current therapeutic approaches. The rational of using traditional hydrogels and SHs in wound healing, as well as the current research directions for developing SHs with innovative features, are addressed and discussed along with their limitations and perspectives in industrial-scale manufacturing.

Exploring the Antioxidant Potential of Gellan and Guar Gums in Wound Healing.

It is acknowledged that the presence of antioxidants boosts the wound-healing process. Many biopolymers have been explored over the years for their antioxidant potential in wound healing, but limited research has been performed on gum structures and their derivatives. This review aims to evaluate whether the antioxidant properties of gellan and guar gums and wound healing co-exist. PubMed was the primary platform used to explore published reports on the antioxidant wound-healing interconnection, wound dressings based on gellan and guar gum, as well as the latest review papers on guar gum. The literature search disclosed that some wound-healing supports based on gellan gum hold considerable antioxidant properties, as evident from the results obtained using different antioxidant assays. It has emerged that the antioxidant properties of guar gum are overlooked in the wound-healing field, in most cases, even if this feature improves the healing outcome. This review paper is the first that examines guar gum vehicles throughout the wound-healing process. Further research is needed to design and evaluate customized wound dressings that can scavenge excess reactive oxygen species, especially in clinical practice.

Optimizing phenol-modified hyaluronic acid for designing shape-maintaining biofabricated hydrogel scaffolds in soft tissue engineering.

In this study, we developed a well-printable biomaterial ink for 3D printing of shape-maintaining hydrogel scaffolds. The hydrogel base comprised tyramine-modified hyaluronic acid (HA-Tyr) and gelatin methacrylate (GelMA) and was dually cross-linked. Using the Box-Behnken design, we explored how varying the ink composition affected fiber formation and shape preservation. By adjusting the polymer ratios, we produced a stable hydrogel with varying responses, from a viscous liquid to a thick gel, and optimized 3D scaffolds that were structurally stable both during and after printing, offering precision and flexibility. Our ink exhibited shear-thinning behavior and high swelling capacity, as well as ECM-like characteristics and biocompatibility, making it an ideal candidate for soft tissues matrices with storage modulus of around 300 Pa. Animal trials and CAM assays confirmed its biocompatibility and integration with host tissue.

Polysaccharides-Calcium Phosphates Composite Beads as Bone Substitutes for Fractures Repair and Regeneration.

The tendency of population aging is continuously increasing, which is directly correlated with a significative number of associated pathologies. Several metabolic bone diseases such as osteoporosis or chronic kidney disease-mineral and bone disorders involve a high risk of fractures. Due to the specific fragility, bones will not self-heal and supportive treatments are necessary. Implantable bone substitutes, a component of bone tissue engineering (BTE) strategy, proved to be an efficient solution for this issue. The aim of this study was to develop composites beads (CBs) with application in the complex field of BTE, by assembling the features of both biomaterials' classes: biopolymers (more specific, polysaccharides: alginate and two different concentrations of guar gum/carboxymethyl guar gum) and ceramics (more specific, calcium phosphates), in a combination described for the first time in the literature. The CBs prepared by double crosslinking (ionic and physically) showed adequate physico-chemical characteristics and capabilities (morphology, chemical structure and composition, mechanical strength, and in vitro behaviour in four different acellular simulated body fluids) for bone tissue repair. Moreover, preliminary in vitro studies on cell cultures highlighted that the CBs were free of cytotoxicity and did not affect the morphology and density of cells. The results indicated that the beads based on a higher concentration of guar gum have superior properties than those with carboxymetilated guar, especially in terms of mechanical properties and behaviour in simulated body fluids.

Experimentally Induced Burns in Rats Treated with Innovative Polymeric Films Type Therapies.

Considering that microbial resistance to antibiotics is becoming an increasingly widespread problem, burn management, which usually includes the use of topical antimicrobial dressings, is still facing difficulties regarding their efficiency to ensure rapid healing. In this context, the main objective of this research is to include new oxytetracycline derivatives in polymeric-film-type dressings for the treatment of wounds caused by experimentally induced burns in rats. The structural and physico-chemical properties of synthesized oxytetracycline derivatives and the corresponding membranes were analyzed by FT-IR and MS spectroscopy, swelling ability and biodegradation capacity. In vitro antimicrobial activity using Gram-positive and Gram-negative bacterial strains and pathogenic yeasts, along with an in vivo study of a burn wound model induced in Wistar rats, was also analyzed. The newly obtained polymeric films, namely chitosan-oxytetracycline derivative membranes, showed good antimicrobial activity noticed in the tested strains, a membrane swelling ratio (MSR) of up to 1578% in acidic conditions and a biodegradation rate of up to 15.7% on day 7 of testing, which are important required characteristics for the tissue regeneration process, after the production of a burn. The in vivo study proved that chitosan-derived oxytetracycline membranes showed also improved healing effects which contributes to supporting the idea of using them for the treatment of wounds caused by burns.

3D high-precision melt electro written polycaprolactone modified with yeast derived peptides for wound healing.

In this study melt electro written (MEW) scaffolds of poly(ε-caprolactone) PCL are decorated with anti-inflammatory yeast-derived peptide for skin wound healing. Initially, 13 different yeast-derived peptides were screened and analyzed using both in vitro and in vivo assays. The MEW scaffolds are functionalized with the selected peptide VLSTSFPPW (VW-9) with the highest activity in reducing pro-inflammatory cytokines and stimulating fibroblast proliferation, migration, and collagen production. The peptide was conjugated to the MEW scaffolds using carbodiimide (CDI) and thiol chemistry, with and without plasma treatment, as well as by directly mixing the peptide with the polymer before printing. The MEW scaffolds modified using CDI and thiol chemistry with plasma treatment showed improved fibroblast and macrophage penetration and adhesion, as well as increased cell proliferation and superior anti-inflammatory properties, compared to the other groups. When applied to full-thickness excisional wounds in rats, the peptide-modified MEW scaffold significantly enhanced the healing process compared to controls (p < 0.05). This study provides proof of concept for using yeast-derived peptides to functionalize biomaterials for skin wound healing.

18F-FDG PET/MRI Imaging in a Preclinical Rat Model of Cardiorenal Syndrome-An Exploratory Study.

Cardiorenal syndrome (CRS) denotes the bidirectional interaction of chronic kidney disease and heart failure with an adverse prognosis but with a limited understanding of its pathogenesis. This study correlates biochemical blood markers, histopathological and immunohistochemistry features, and 2-deoxy-2-fluoro-D-glucose positron emission tomography (18F-FDG PET) metabolic data in low-dose doxorubicin-induced heart failure, cardiorenal syndrome, and renocardiac syndrome induced on Wistar male rats. To our knowledge, this is the first study that investigates the underlying mechanisms for CRS progression in rats using 18F-FDG PET. Clinical, metabolic cage monitoring, biochemistry, histopathology, and immunohistochemistry combined with PET/MRI (magnetic resonance imaging) data acquisition at distinct points in the disease progression were employed for this study in order to elucidate the available evidence of organ crosstalk between the heart and kidneys. In our CRS model, we found that chronic treatment with low-dose doxorubicin followed by acute 5/6 nephrectomy incurred the highest mortality among the study groups, while the model for renocardiac syndrome resulted in moderate-to-high mortality. 18F-FDG PET imaging evidenced the doxorubicin cardiotoxicity with vascular alterations, normal kidney development damage, and impaired function. Given the fact that standard clinical markers were insensitive to early renal injury, we believe that the decreasing values of the 18F-FDG PET-derived renal marker across the groups and, compared with their age-matched controls, along with the uniform distribution seen in healthy developing rats, could have a potential diagnostic and prognostic yield in cardiorenal syndrome.

Borrowing the Features of Biopolymers for Emerging Wound Healing Dressings: A Review.

Wound dressing design is a dynamic and rapidly growing field of the medical wound-care market worldwide. Advances in technology have resulted in the development of a wide range of wound dressings that treat different types of wounds by targeting the four phases of healing. The ideal wound dressing should perform rapid healing; preserve the body's water content; be oxygen permeable, non-adherent on the wound and hypoallergenic; and provide a barrier against external contaminants-at a reasonable cost and with minimal inconvenience to the patient. Therefore, choosing the best dressing should be based on what the wound needs and what the dressing does to achieve complete regeneration and restoration of the skin's structure and function. Biopolymers, such as alginate (ALG), chitosan (Cs), collagen (Col), hyaluronic acid (HA) and silk fibroin (SF), are extensively used in wound management due to their biocompatibility, biodegradability and similarity to macromolecules recognized by the human body. However, most of the formulations based on biopolymers still show various issues; thus, strategies to combine them with molecular biology approaches represent the future of wound healing. Therefore, this article provides an overview of biopolymers' roles in wound physiology as a perspective on the development of a new generation of enhanced, naturally inspired, smart wound dressings based on blood products, stem cells and growth factors.

Acrylate-endcapped urethane-based hydrogels: An in vivo study on wound healing potential.

Improving wound healing by developing innovative dressing materials has been an important focus over the past few years in the biomedical field. In this regard, the current study focuses on developing new dressings based on acrylate-endcapped urethane-based polymers (AUPs). The materials have been processed into films and electrospun mats. Exudate uptake capacity, mechanical properties and fiber morphology were evaluated herein. The results showed superior uptake capacity of both films and mats when compared to Aquacel®Ag, Exufiber® and Help®. Addition of a high molar mass poly(ethylene glycol) to the AUP polymers benefits both the film and electrospun dressings in terms of flexibility and elongation. An in vivo study was conducted to assess the wound healing properties of these dressings on an acute wound model induced to rats. A macroscopic evaluation indicated that wound contraction and wound fraction percentages were improved significantly in case of the AUP-materials when compared to both the positive (Aquacel®Ag) and negative (Exufiber® and Help®) controls. A histopathological assay, to underline the changes noticed on a macroscopical level, was also performed. The data obtained proved that the developed dressings are beneficial towards tissue regeneration and accelerated wound healing. These findings offer a practical yet adequate strategy for the fabrication of acrylate-endcapped urethane-based materials for wound healing applications.

Gelatin-Based Versus Alginate-Based Hydrogels: Providing Insight in Wound Healing Potential.

Wound dressings under the form of films constituted of modified alginate (methacrylated alginate - AlgMA) versus a gelatine derivative containing norbornene functionalities (GelNB) are developed and evaluated for their moisturizing effects, followed by further in vivo testing to assay their wound healing potential. The gel fraction results shows that AlgMA and GelNB films displayed a high crosslinking efficiency while the swelling assay reveals a stronger water uptake capacity for AlgMA films compared to GelNB and to commercial dressing AquacelAg, used as positive control. Referring to the in vivo wound healing effect, the GelNB films not only exhibit proper healing properties, yet is higher to the AquacelAg, while the AlgMA films exhibit similar wound healing effect as the positive control. On a microscopic level, the healing phases (from inflammation to proliferation and contraction) are present for both materials, yet at a faster rate for the GelNB films, which is in line with the macroscopic findings. These results provide data which support that GelNB films outperform AlgMA films, but both can be used for wound healing applications.

Imaging Constructs: The Rise of Iron Oxide Nanoparticles.

Over the last decade, an important challenge in nanomedicine imaging has been the work to design multifunctional agents that can be detected by single and/or multimodal techniques. Among the broad spectrum of nanoscale materials being investigated for imaging use, iron oxide nanoparticles have gained significant attention due to their intrinsic magnetic properties, low toxicity, large magnetic moments, superparamagnetic behaviour and large surface area-the latter being a particular advantage in its conjunction with specific moieties, dye molecules, and imaging probes. Tracers-based nanoparticles are promising candidates, since they combine synergistic advantages for non-invasive, highly sensitive, high-resolution, and quantitative imaging on different modalities. This study represents an overview of current advancements in magnetic materials with clinical potential that will hopefully provide an effective system for diagnosis in the near future. Further exploration is still needed to reveal their potential as promising candidates from simple functionalization of metal oxide nanomaterials up to medical imaging.

Duplex echography as an adjuvant tool to clinical examination to detect early postoperative free flap vascular compromise.

BACKGROUND: Clinical examination remains the cornerstone for postoperative monitoring of free flaps but is highly dependent on the surgeon's ability and experience. Duplex echography provides a noninvasive objective evaluation of tissue perfusion. The authors hypothesized that duplex echography may be a more sensitive and specific monitoring method for early detection of postoperative flap compromise compared to clinical examination alone. The goal was to evaluate any differences between combined duplex echography and clinical examination flap monitoring versus isolated clinical evaluation. METHODS: A total of 730 free flaps in 700 patients were included in the study. We conducted an intra-subject prospective study of a cohort of patients who underwent free flap reconstruction in our unit to compare clinical examination with duplex echography for postoperative monitoring. An inter-subject study was also undertaken comparing the prospective cohort with a historical control group of patients in whom free flap monitoring was made using clinical examination alone. The patency flow and velocities through the artery and vein of the flap were measured at the donor and recipient vessels of every anastomosis by duplex scanning, by the same plastic surgeon every 4 hr, during the first 18 hr after surgery. RESULTS: Duplex echography and clinical evaluation were used in 175 patients. The historical cohort included a total of 525 flaps. Every patient with suspicion of vascular compromise based on duplex echography was taken back for surgical re-exploration. There were no cases of overdiagnosis using duplex echography (Sensitivity 100%, Specificity 100%). Clinical evaluation detected issues with the vascularan astomoses in 23/175 flaps. However, it failed to detect 12/22 cases which presented with vascular complications and gave a false indication of possible complications in 13 flaps (Sensitivity 45%, Specificity 92%). CONCLUSION: In our practice, duplex echography is considered a useful adjunct monitoring tool for early detection of postoperative flap compromise, which compliments clinical evaluation. It provides anatomic and hemodynamic information of the vascular status and may therefore increase survival of flaps by allowing earlier detection of vascular compromise, compared to clinical examination alone, in postoperative monitoring of free flaps.

Role of Ultrahigh Frequency Ultrasound in Evaluating Experimental Flaps.

BACKGROUND: Experimental flap follow-up needs faster, safer, and less invasive techniques that can be easily correlated to clinical procedures. For this reason, we aimed to test the role of ultrahigh frequency ultrasound in follow-up of flap viability. Further on, we aimed to analyze if the chimeric groin flap can be mobilized in a sandwiched position without affecting its vascular supply by twisting its pedicle. METHODS: A total of 12 male Wistar rats, split into three groups, were used. Group A (n = 4) had the chimeric groin flap repositioned in a sandwich position on the anterior abdominal wall and underwent ultrahigh frequency ultrasound follow-up at days 10 and 14. Group B (n = 4) also had the flaps sandwiched, however, at day 14 the vascularity of flaps was proven by infusion of nontargeted ultrasound contrast agents, after which flaps were sent for histological analysis. Group C (C1 n = 2, C2 n = 2) was the control group. In C1 the chimeric groin flap was harvested and sent for histology on day 0, acting as a histological benchmark of flap viability, and in C2 the chimeric groin flap was re-sutured in its anatomical position and after 14 days, flaps were harvested and sent for histological analysis, acting as a direct control for Group B. RESULTS: Ultrasound showed constant vascular flow in both adipose and skin flaps in the sandwiched position. Microbubble study showed diffuse perfusion within flaps. Ultrasound measurements of flow velocity, flap volume, and percentage of vascularity showed a decrease in flap volume and increase in vascularity over 14 days. Histology showed similar viability in both groups. CONCLUSION: Ultrahigh frequency ultrasound may be a valuable tool for postoperative flap assessment, while the chimeric flap can be moved freely in a sandwich position making it suitable for adding tissue substitutes within its components.

New Chimeric Groin Flap: Experimental Model in Rats.

AIM: Increased emphasis is on using tissue substitutes and stem cells to improve flap applicability and survival rates. To accomplish this, the first step is to have a versatile experimental flap, easy to harvest and use as a template. We sought to develop a reliable experimental chimeric groin flap with free mobility and reliable bloods supply that can be twisted, relocated, and integrated easily with other materials. MATERIALS AND METHODS: Ten male Wistar rats were included. The flap consists of a 2.5-cm skin paddle centered on the medial branch of the inferior epigastric artery and a 4.5/2-cm fat pad supplied by the lateral branch of the inferior epigastric artery. After being raised, flaps were resutured in their anatomical position. Flaps were followed up for 15 days. At the end of the study, the viability of flaps was analyzed by ultrahigh-frequency ultrasound, nontargeted contrast study, and histology assessment. RESULTS: All flaps survived without significant complications. Nontargeted microbubbles spread evenly in both the superficial and deep flap. Ultrasound assessment at day 15 showed no significant areas of necrosis or edema. Histology examination of 3 random flaps confirmed vessel patency and flap viability. CONCLUSION: We propose a simple, easy to harvest and reliable experimental flap which offers a main advantage of all-around mobility through its chimeric design. It is a suitable model for bioengineering studies as it can be used as a template for integration of tissue substitutes or stem cells, between its 2 components.

Nanomaterials Designed for Antiviral Drug Delivery Transport across Biological Barriers.

Viral infections are a major global health problem, representing a significant cause of mortality with an unfavorable continuously amplified socio-economic impact. The increased drug resistance and constant viral replication have been the trigger for important studies regarding the use of nanotechnology in antiviral therapies. Nanomaterials offer unique physico-chemical properties that have linked benefits for drug delivery as ideal tools for viral treatment. Currently, different types of nanomaterials namely nanoparticles, liposomes, nanospheres, nanogels, nanosuspensions and nanoemulsions were studied either in vitro or in vivo for drug delivery of antiviral agents with prospects to be translated in clinical practice. This review highlights the drug delivery nanosystems incorporating the major antiviral classes and their transport across specific barriers at cellular and intracellular level. Important reflections on nanomedicines currently approved or undergoing investigations for the treatment of viral infections are also discussed. Finally, the authors present an overview on the requirements for the design of antiviral nanotherapeutics.

Vibrational Spectroscopy Fingerprinting in Medicine: from Molecular to Clinical Practice.

In the last two decades, Fourier Transform Infrared (FTIR) and Raman spectroscopies turn out to be valuable tools, capable of providing fingerprint-type information on the composition and structural conformation of specific molecular species. Vibrational spectroscopy's multiple features, namely highly sensitive to changes at the molecular level, noninvasive, nondestructive, reagent-free, and waste-free analysis, illustrate the potential in biomedical field. In light of this, the current work features recent data and major trends in spectroscopic analyses going from in vivo measurements up to ex vivo extracted and processed materials. The ability to offer insights into the structural variations underpinning pathogenesis of diseases could provide a platform for disease diagnosis and therapy effectiveness evaluation as a future standard clinical tool.