Highly porous drug-eluting structures: from wound dressings to stents and scaffolds for tissue regeneration

Developmental prospects of carrageenan-based wound dressing films: Unveiling techno-functional properties and freeze-drying technology for the development of absorbent films - A review

This review explores the intricate wound healing process, emphasizing the critical role of dressing material selection, particularly for chronic wounds with high exudate levels. The aim is to tailor biodegradable dressings for comprehensive healing, focusing on maximizing moisture retention, a vital element for adequate recovery. Researchers are designing advanced wound dressings that enhance techno-functional and bioactive properties, minimizing healing time and ensuring cost-effective care. The study delves into wound dressing materials, highlighting carrageenan biocomposites superior attributes and potential in advancing wound care. Carrageenan's versatility in various biomedical applications demonstrates its potential for tissue repair, bone regeneration, and drug delivery. Ongoing research explores synergistic effects by combining carrageenan with other novel materials, aiming for complete biocompatibility. As innovative solutions emerge, carrageenan-based wound-healing medical devices are poised for global accessibility, addressing challenges associated with the complex wound-healing process. The exceptional physico-mechanical properties of carrageenan make it well-suited for highly exudating wounds, offering a promising avenue to revolutionize wound care through freeze-drying techniques. This thorough approach to evaluating the wound healing effectiveness of carrageenan-based films, particularly emphasizing the development potential of lyophilized films, has the potential to significantly improve the quality of life for patients receiving wound healing treatments.

The Development and Characterisation of a P(3HB-co-4HB)-Bioactive Glass-Graphene Hydrogel as a Potential Formulation for Biomedical and Therapeutical Translation

The clinical management of wounds is known to be a significant challenge: not only does the dressing need to ensure and provide the appropriate barrier and healing characteristics, but consideration of patient compliance concerning comfort, functionality, and practicality also needs to be included. The poly(3-hydroxybutyrate-co-4-hydroxubutyrate) (P(3HB-co-4HB)) copolymer, isolated from Cupriavidus malaysiensis USM1020 (C. malaysiensis USM1020), was produced in the presence of excess carbon sources (1,4-butanediol and 1,6-hexanediol) using either a shake flask cultivation process or a bioreactor fermentation system. P(3HB-co-4HB) is widely known to be biodegradable and highly biocompatible and contains a tuneable 4HB monomer molar fraction, which is known to affect the final physicochemical properties of the intracellular copolymer. In this paper, we describe not only the fabrication of the polymeric gel but also its optimised profiling using a range of physical and mechanical techniques, i.e., SEM, FTIR, DMA, DSC, and WCA. The further enhancement of the gel through additional functionalisation with sol-gel-derived bioactive glass and liquid-exfoliated graphene was also investigated. The biocompatibility and biological characterisation of the substrates was assessed using murine osteoblasts (MC3T3), human primary dermal fibroblasts (HDFs), human fibroblast (BJ) cells, and standard cell culture assays (i.e., metabolic activity, LDH release, and live/dead staining). In short, P(3HB-co-4HB) was successfully isolated from the bacteria, with the defined physico-chemical profiles dependent on the culture substrate and culturing platform used. The additional enhancement of the copolymer with bioactive glass and/or graphene was also demonstrated by varying the combination loading of the materials, i.e., graphene resulted in an increase in tensile strength (~11 MPa) and the wettability increased following the incorporation of bioactive glass and 0.01 wt% graphene (WCA ~46.3°). No detrimental effects in terms of biocompatibility were noticed during the 7 days of culture in the primary and established cell lines. This study demonstrates the importance of optimising each of the individual components within the biocomposite and their relationship concerning the fine-tuning of the material's properties, thus targeting and impacting the endpoint application.

Sugarcane Bagasse-Derived Cellulose Nanocrystal/Polyvinyl Alcohol/Gum Tragacanth Composite Film Incorporated with Betel Leaf Extract as a Versatile Biomaterial for Wound Dressing

In this study, nanocomposite film was fabricated using cellulose nanocrystals (CNCs) as nanofiller in a polymer matrix of polyvinyl alcohol (PVA) and gum tragacanth (GT) via solution casting. CNCs were extracted from sugarcane bagasse using a steam explosion technique followed by acid hydrolysis. Initial analysis of CNCs by transmission electron microscopy (TEM) showed nanosized particles of 104 nm in length and 7 nm in width. Physical and chemical characteristics of neat PVA, PVA/GT, and PVA/GT/CNC films with varying concentrations of CNCs (from 2% to 10%) were analyzed by the scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrometry, mechanical test, and swelling test. The SEM analysis showed cluster formation of CNCs in the polymer matrix at high concentration. The developed films were transparent. FTIR spectrometry analysis confirmed the chemical functional groups of the various components in the film. The presence of GT and CNCs in the polymer matrix improved the characteristics of films as evident in the prolonged stability for 7 days and increased mechanical properties. The highest elastic modulus of 1526.11 ± 31.86 MPa and tensile strength of 80.39 MPa were recorded in PVA/GT/CNC2 film. The swelling ability, however, decreased from 260% to 230%. Cytotoxicity analysis of the PVA/GT/CNC film showed that it is nontoxic to mouse fibroblast cells L929 with 95% cell viability. Films loaded with betel leaf extract exhibited excellent antibacterial activities against Staphylococcus aureus DMST 8840 and Pseudomonas aeruginosa TISTR 781 with 28.20 ± 0.84 mm and 23.60 ± 0.55 mm inhibition zones, respectively. These results demonstrate that PVA/GT/CNC loaded with the betel leaf extract could act as promising and versatile wound dressings to protect the wound surface from infection and dehydration.

Emulsion templated scaffolds of poly(ε-caprolactone) - a review

The role of poly(ε-caprolactone) (PCL) and its 3D scaffolds in tissue engineering has already been established due to its ease of processing into long-term degradable implants and approval from the FDA. This review presents the role of high internal phase emulsion (HIPE) templating in the fabrication of PCL scaffolds, and the versatility of the technique along with challenges associated with it. Considering the huge potential of HIPE templating, which so far has mainly been focused on free radical polymerization of aqueous HIPEs, we provide a summary of how the technique has been expanded to non-aqueous HIPEs and other modes of polymerization such as ring-opening. The scope of coupling of HIPE templating with some of the advanced fabrication methods such as 3D printing or electrospinning is also explored.

Mechanical properties, in vitro and in vivo biocompatibility analysis of pure iron porous implant produced by metal injection molding: A new eco-friendly feedstock from natural rubber (Hevea brasiliensis)

Metal injection molding (MIM) has become an important manufacturing technology for biodegradable medical devices. As a biodegradable metal, pure iron is a promising biomaterial due to its mechanical properties and biocompatibility. In light of this, we performed the first study that manufactured and evaluated the in vitro and in vivo biocompatibility of samples of iron porous implants produced by MIM with a new eco-friendly feedstock from natural rubber (Hevea brasiliensis), a promisor binder that provides elastic property in the green parts. The iron samples were submitted to tests to determine density, microhardness, hardness, yield strength, and stretching. The biocompatibility of the samples was studied in vitro with adipose-derived mesenchymal stromal cells (ADSCs) and erythrocytes, and in vivo on a preclinical model with Wistar rats, testing the iron samples after subcutaneous implant. Results showed that the manufactured samples have adequate physical, and mechanical characteristics to biomedical devices and they are cytocompatible with ADSCs, hemocompatible and biocompatible with Wistars rats. Therefore, pure iron produced by MIM can be considered a promising material for biomedical applications.

Preparation of a Hydrogel Nanofiber Wound Dressing

The study addressed the production of a hydrogel nanofiber skin cover and included the fabrication of hydrogel nanofibers from a blend of polyvinyl alcohol and alginate. The resulting fibrous layer was then crosslinked with glutaraldehyde, and, after 4 h of crosslinking, although the gelling component, i.e., the alginate, crosslinked, the polyvinyl alcohol failed to do so. The experiment included the comparison of the strength and ductility of the layers before and after crosslinking. It was determined that the fibrous layer following crosslinking evinced enhanced mechanical properties, which acted to facilitate the handling of the material during its application. The subsequent testing procedure proved that the fibrous layer was not cytotoxic. The study further led to the production of a modified hydrogel nanofiber layer that combined polyvinyl alcohol with alginate and albumin. The investigation of the fibrous layers produced determined that following contact with water the polyvinyl alcohol dissolved leading to the release of the albumin accompanied by the swelling of the alginate and the formation of a hydrogel.

Evaluation of in vitro and in vivo biocompatibility of iron produced by powder metallurgy

Biodegradable metallic materials (BMMs) are expected to corrode gradually in vivo after providing the structural support to the tissue during its regeneration and healing processes. These characteristics make them promising candidates for use in stents. These endoprostheses are produced from metal alloys by casting and thermomechanical treatment. Since porous alloys and metals have less corrosion resistance than dense ones, the use of powder metallurgy becomes an option to produce them. Among the metals, iron has been proposed as a material in the manufacturing of stents because of its mechanical properties. However, even then it is unclear what toxicity threshold is safe to the body. Thus, the objective of this research was to verify the biocompatibility of sintered 99.95% and 99.5% pure iron by powder metallurgy in vitro with Adipose-derived mesenchymal stromal cells (ADSCs) and in vivo with a Wistar rat model. Herein, characterizations of iron powder samples produced by the powder metallurgy and the process parameters as compression pressure, atmosphere, sintering time and temperature were determined to evaluate the potential of production of biodegradable implants. The samples obtained from pure iron were submitted to tests of green and sintered density, porosity, microhardness, hardness and metallography. The biocompatibility study was performed by indirect and direct cell culture with iron. The effects of corrosion products of iron on morphology, viability, and proliferation of ADSCs were evaluated in vitro. Hemolysis assay was performed to verify the hemocompatibility of the samples. In vivo biocompatibility was evaluated after pure iron discs were implanted subcutaneously into the dorsal area of Wistar rats that were followed up to 6 months. The results presented in this paper validated the potential to produce biodegradable medical implants by powder metallurgy. Both iron samples were hemocompatible and biocompatible in vitro and in vivo, although the 99.95% iron had better performance in vitro than 99.5%.

Nanostructured Fibers Containing Natural or Synthetic Bioactive Compounds in Wound Dressing Applications

The interest in wound healing characteristics of bioactive constituents and therapeutic agents, especially natural compounds, is increasing because of their therapeutic properties, cost-effectiveness, and few adverse effects. Lately, nanocarriers as a drug delivery system have been actively investigated and applied in medical and therapeutic applications. In recent decades, researchers have investigated the incorporation of natural or synthetic substances into novel bioactive electrospun nanofibrous architectures produced by the electrospinning method for skin substitutes. Therefore, the development of nanotechnology in the area of dressings that could provide higher performance and a synergistic effect for wound healing is needed. Natural compounds with antimicrobial, antibacterial, and anti-inflammatory activity in combination with nanostructured fibers represent a future approach due to the increased wound healing process and regeneration of the lost tissue. This paper presents different approaches in producing electrospun nanofibers, highlighting the electrospinning process used in fabricating innovative wound dressings that are able to release natural and/or synthetic substances in a controlled way, thus enhancing the healing process.

Chitosan-laponite nanocomposite scaffolds for wound dressing application

The pivotal issue of skin regeneration research is the development of effective biomaterials that exhibit biological activities as fungicide and bactericide, combining simple and low cost manufacturing technologies. In this context, nanocomposite scaffolds based on chitosan (Ch)/Laponite (Lap) were produced by using different concentrations of Lap via freeze-drying process for potential application in skin regeneration. The influence of Lap concentration on the scaffold properties was evaluated. The prepared scaffolds were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), porosity, swelling capacity, and mechanical analyses. The results revealed that the scaffolds exhibited a porous architecture, besides the increase in the clay content, leads to an increase in the porosity, an improvement of mechanical strength, and a decrease of swelling capacity. In vitro tests were also carried out to evaluate the biocompatibility of the materials, such as bioadhesion, antibacterial activity, viability, and cell adhesion. Viability and cell adhesion demonstrated that all scaffolds were not cytotoxic and the fibroblast cells readily attached on the surface of the scaffolds. Thereby, the results suggested that the nanocomposite scaffolds are biomaterials potentially useful as wound dressings.

3D printed Polycaprolactone scaffolds with dual macro-microporosity for applications in local delivery of antibiotics

Advanced scaffolds used in tissue regenerating applications should be designed to address clinically relevant complications such as surgical site infection associated with surgical procedures. Recognizing that patient-specific scaffolds with local drug delivery capabilities are a promising approach, we combined 3D printing with traditional salt-leaching techniques to prepare a new type of scaffold with purposely designed macro- and micro-porosity. The dual macro/micro porous scaffolds of medical-grade polycaprolactone (mPCL) were characterized for their porosity, surface area, mechanical properties and degradation. The use of these scaffolds for local prophylactic release of Cefazolin to inhibit S. aureus growth was investigated as an example of drug delivery with this versatile platform. The introduction of microporosity and increased surface area allowed for loading of the scaffold using a simple drop-loading method of this heat-labile antibiotic and resulted in significant improvement in its release for up to 3 days. The Cefazolin released from scaffolds retained its bioactivity similar to that of fresh Cefazolin. There were no cytotoxic effects in vitro against 3 T3 fibroblasts at Cefazolin concentration of up to 100 μg/ml and no apparent effects on blood clot formation on the scaffolds in vitro. This study therefore presents a novel type of scaffolds with dual macro- and micro-porosity manufactured by a versatile method of 3D printing combined with salt-leaching. These scaffolds could be useful in tissue regeneration applications where it is desirable to prevent complications using local delivery of drugs.

Fabrication and hemocompatibility assessment of novel polyurethane-based bio-nanofibrous dressing loaded with honey and Carica papaya extract for the management of burn injuries

Management of burn injury is an onerous clinical task since it requires continuous monitoring and extensive usage of specialized facilities. Despite rapid improvizations and investments in burn management, >30% of victims hospitalized each year face severe morbidity and mortality. Excessive loss of body fluids, accumulation of exudate, and the development of septic shock are reported to be the main reasons for morbidity in burn victims. To assist burn wound management, a novel polyurethane (PU)-based bio-nanofibrous dressing loaded with honey (HN) and Carica papaya (PA) fruit extract was fabricated using a one-step electrospinning technique. The developed dressing material had a mean fiber diameter of 190±19.93 nm with pore sizes of 4–50 µm to support effective infiltration of nutrients and gas exchange. The successful blending of HN- and PA-based active biomolecules in PU was inferred through changes in surface chemistry. The blend subsequently increased the wettability (14%) and surface energy (24%) of the novel dressing. Ultimately, the presence of hydrophilic biomolecules and high porosity enhanced the water absorption ability of the PU-HN-PA nanofiber samples to 761.67% from 285.13% in PU. Furthermore, the ability of the bio-nanofibrous dressing to support specific protein adsorption (45%), delay thrombus formation, and reduce hemolysis demonstrated its nontoxic and compatible nature with the host tissues. In summary, the excellent physicochemical and hemocompatible properties of the developed PU-HN-PA dressing exhibit its potential in reducing the clinical complications associated with the treatment of burn injuries.

Smart Dressings Based on Nanostructured Fibers Containing Natural Origin Antimicrobial, Anti-Inflammatory, and Regenerative Compounds

A fast and effective wound healing process would substantially decrease medical costs, wound care supplies, and hospitalization significantly improving the patients' quality of life. The search for effective therapeutic approaches seems to be imperative in order to avoid the aggravation of chronic wounds. In spite of all the efforts that have been made during the recent years towards the development of artificial wound dressings, none of the currently available options combine all the requirements necessary for quick and optimal cutaneous regeneration. Therefore, technological advances in the area of temporary and permanent smart dressings for wound care are required. The development of nanoscience and nanotechnology can improve the materials and designs used in topical wound care in order to efficiently release antimicrobial, anti-inflammatory and regenerative compounds speeding up the endogenous healing process. Nanostructured dressings can overcome the limitations of the current coverings and, separately, natural origin components can also overcome the drawbacks of current antibiotics and antiseptics (mainly cytotoxicity, antibiotic resistance, and allergies). The combination of natural origin components with demonstrated antibiotic, regenerative, or anti-inflammatory properties together with nanostructured materials is a promising approach to fulfil all the requirements needed for the next generation of bioactive wound dressings. Microbially compromised wounds have been treated with different essential oils, honey, cationic peptides, aloe vera, plant extracts, and other natural origin occurring antimicrobial, anti-inflammatory, and regenerative components but the available evidence is limited and insufficient to be able to draw reliable conclusions and to extrapolate those findings to the clinical practice. The evidence and some promising preliminary results indicate that future comparative studies are justified but instead of talking about the beneficial or inert effects of those natural origin occurring materials, the scientific community leads towards the identification of the main active components involved and their mechanism of action during the corresponding healing, antimicrobial, or regenerative processes and in carrying out systematic and comparative controlled tests. Once those natural origin components have been identified and their efficacy validated through solid clinical trials, their combination within nanostructured dressings can open up new avenues in the fabrication of bioactive dressings with outstanding characteristics for wound care. The motivation of this work is to analyze the state of the art in the use of different essential oils, honey, cationic peptides, aloe vera, plant extracts, and other natural origin occurring materials as antimicrobial, anti-inflammatory and regenerative components with the aim of clarifying their potential clinical use in bioactive dressings. We conclude that, for those natural occurring materials, more clinical trials are needed to reach a sufficient level of evidence as therapeutic agents for wound healing management.

Novel bioresorbable stent coating for drug release in congenital heart disease applications

A novel double opposed helical poly-l-lactic acid (PLLA) bioresorbable stent has been designed for use in pediatrics. The aim was to test the PLLA stent biocompatibility. The PLLA stent was immersed into whole pig's blood in a closed loop circuit then fibrin and platelet association was assessed via enzyme-linked immunosorbent assay. D-Dimer was valued at 0.2 ± 0.002 ng/mL and P-selectin 0.43 ± 00.01 ng/mL indicating limited association of fibrin and platelets on the stent. To improve biocompatibility by targeting inflammatory cells, dexamethasone was incorporated on PLLA fibers with two coating methods. Both coatings were poly(l-lactide-co-glycolide) acid (PLGA) but one was made porous with sucrose while the other remained nonporous. There was no change in mechanical properties of the fiber with either coating of PLGA polymer. The total amount of dexamethasone released was then determined for each coating. The cumulative drug release for the porous fiber was significantly higher (∼100%) over 8 weeks than the nonporous fiber (40%). Surface examination of the fiber with scanning electron microscopy showed more surface microfracturing in coatings that contain pores. The biocompatibility of this novel stent was demonstrated. Mechanical properties of the fiber were not altered by coating with PLGA polymer. Anti-inflammatory drug release was optimized using a porous PLGA polymer.