Cilostazol-Loaded Poly(ε-Caprolactone) Electrospun Drug Delivery System for Cardiovascular Applications

Electrospinning in Drug Delivery: Progress and Future Outlook

There is intense research during the past few decades to design and fabricate drug delivery systems using the electrospinning system. Electrospinning is an efficient technique to produce nanofiber materials with different dimensions and morphologies by adjusting the processing parameters. Electrospinning is becoming an innovative technology that promotes the pursuit and maintenance of human health. Herein, the review discusses the contribution of electrospinning technology in drug delivery systems, summarising the modification of the various electrospinning system configurations and the effects of the process parameters on fibers, their application in drug delivery including carrier materials, loaded drugs and their release mechanisms and illustrates their various medical applications. Finally, this review discusses the challenges, bottlenecks, and development prospects of electrospinning technology in the field of drug delivery in terms of scaling up for clinical use and exploring potential solutions to pave the way to establish electrospinning for future drug delivery systems.

Physical Properties for Novel Cilostazol Co-amorphous; Effect of Preparation Method and Molar Ratio on the Co-amorphous

Co-amorphous materials have gained special attention in the pharmaceutical field due to their high potential to enhance the oral bioavailability of poorly aqueous soluble drugs. In co-amorphous studies, few reports have examined the physical properties and molecular states of different active pharmaceutical ingredients (APIs) : co-amorphous former (CF) molar ratios and preparation methods. Therefore, we investigated the effect of molar ratio and preparation method on the physical properties of a novel co-amorphous system consisting of cilostazol and l-tryptophan, which we identified through screening. Co-amorphous consisting of molar ratios of 1 : 1 (co-milling (CM) 1 : 1), 1 : 1.5 (CM 1 : 1.5), and 1 : 2 (CM 1 : 2) were prepared by the CM method, while samples with a molar ratio of 1 : 1 (spray drying (SD) 1 : 1) were prepared by the spray drying method. CM 1 : 1.5 and CM 1 : 2 showed the highest solubility. Storage stability was excellent for CM 1:1.5, CM 1 : 2, and SD 1 : 1, whereas physical properties were improved by co-amorphization. To investigate the factors responsible for the improved physical properties, the molecular state of the co-amorphous system was evaluated, and it was inferred that hydrogen bonds were formed between cilostazol and l-tryptophan. Solid-state 13C-NMR showed several new peaks specific to the solid state in the co-milled sample compared to SD 1 : 1 and cilostazol amorphous, suggesting that the molecular state may differ depending on the preparation method. As described above, different physical properties and molecular states were observed in the novel co-amorphous system consisting of cilostazol and l-tryptophan when the molar ratio of APIs and CF, and the preparation method differed.

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.

Pharmaceutical/Biomedical Applications of Electrospun Nanofibers - Comprehensive Review, Attentive to Process Parameters and Patent Landscape

Nanotechnology is a new science and business endeavour with worldwide economic benefits. Growing knowledge of nanomaterial fabrication techniques has increased the focus on nanomaterial preparation for various purposes. Nanofibers are one-dimensional nanomaterials having distinct physicochemical properties and characteristics. Nanofibers are nanomaterial types with a cross-sectional dimension of tens to hundreds of nanometres. They may create high porosity mesh networks with significant interconnections among pores, making them suitable for advanced applications. Electrospinning stands out for its ease of use, flexibility, low cost, and variety among the approaches described in the literature. The most common method for making nanofibers is electrospinning. This article extensively describes and summarizes the impact of various process variables on the fabrication of nanofibers. Special attention has been given to scientific and patent prospection to confirm the research interests in nanofibers.

Solid implantable devices for sustained drug delivery

Implantable drug delivery systems (IDDS) are an attractive alternative to conventional drug administration routes. Oral and injectable drug administration are the most common routes for drug delivery providing peaks of drug concentrations in blood after administration followed by concentration decay after a few hours. Therefore, constant drug administration is required to keep drug levels within the therapeutic window of the drug. Moreover, oral drug delivery presents alternative challenges due to drug degradation within the gastrointestinal tract or first pass metabolism. IDDS can be used to provide sustained drug delivery for prolonged periods of time. The use of this type of systems is especially interesting for the treatment of chronic conditions where patient adherence to conventional treatments can be challenging. These systems are normally used for systemic drug delivery. However, IDDS can be used for localised administration to maximise the amount of drug delivered within the active site while reducing systemic exposure. This review will cover current applications of IDDS focusing on the materials used to prepare this type of systems and the main therapeutic areas of application.

Effects of Poloxamers as Excipients on the Physicomechanical Properties, Cellular Biocompatibility, and In Vitro Drug Release of Electrospun Polycaprolactone (PCL) Fibers

Electrospun microfibers are emerging as one of the advanced wound dressing materials for acute and/or chronic wounds, especially with their ability to carry drugs and excipients at a high loading while being able to deliver them in a controlled manner. Various attempts were made to include excipients in electrospun microfibers as wound dressing materials, and one of them is poloxamer, an amphiphilic polymer that exhibits wound debridement characteristics. In this study, we formulated two types of poloxamers (i.e., P188 and P338) at 30% (w/w) loading into electrospun polycaprolactone (PCL) fibers to evaluate their physicomechanical properties, biocompatibility, and in vitro drug release of a model drug. Our findings showed that the incorporation of poloxamers in the PCL solutions during electrospinning resulted in a greater "whipping" process for a larger fiber deposition area. These fibers were mechanically stiffer and stronger, but less ductile as compared to the PCL control fibers. The incorporation of poloxamers into electrospun PCL fibers reduced the surface hydrophobicity of fibers according to our water contact angle studies and in vitro degradation studies. The fibers' mechanical properties returned to those of the PCL control groups after "dumping" the poloxamers. Moreover, poloxamer-loaded PCL fibers accelerated the in vitro release of the model drug due to surface wettability. These poloxamer-loaded PCL fibers were biocompatible, as validated by MTT assays using A549 cells. Overall, we demonstrated the ability to achieve a high loading of poloxamers in electrospun fibers for wound dressing applications. This work provided the basic scientific understanding of materials science and bioengineering with an emphasis on the engineering applications of advanced wound dressings.

Electrospun Materials Based on Polymer and Biopolymer Blends-A Review

This review covers recent developments and progress in polymer and biopolymer blending and material preparation by electrospinning. Electrospinning is a technique that is used to produce nanofibers to improve the quality of membranes. Electrospun nanofibers are highly applicable in biomedical sciences, supercapacitors, and in water treatment following metal ion adsorption. The key affecting factors of electrospinning have been checked in the literature to obtain optimal conditions of the electrospinning process. Future research directions and outlooks have been suggested to think about innovative ideas for research in this field.

Drug loaded implantable devices to treat cardiovascular disease

INTRODUCTION

It is widely acknowledged that cardiovascular diseases (CVDs) continue to be the leading cause of death globally. Furthermore, CVDs are the leading cause of diminished quality of life for patients, frequently as a result of their progressive deterioration. Medical implants that release drugs into the body are active implants that do more than just provide mechanical support; they also have a therapeutic role. Primarily, this is achieved through the controlled release of active pharmaceutical ingredients (API) at the implementation site.

AREAS COVERED

In this review, the authors discuss drug-eluting stents, drug-eluting vascular grafts, and drug-eluting cardiac patches with the aim of providing a broad overview of the three most common types of cardiac implant.

EXPERT OPINION

Drug eluting implants are an ideal alternative to traditional drug delivery because they allow for accurate drug release, local drug delivery to the target tissue, and minimise the adverse side effects associated with systemic administration. Despite the fact that there are still challenges that need to be addressed, the ever-evolving new technologies are making the fabrication of drug eluting implants a rewarding therapeutic endeavour with the possibility for even greater advances.

Fabrication and Characterisation of 3D-Printed Triamcinolone Acetonide-Loaded Polycaprolactone-Based Ocular Implants

Triamcinolone acetonide (TA) is a corticosteroid that has been used to treat posterior segment eye diseases. TA is injected intravitreally in the management of neovascular disorders; however, frequent intravitreal injections result in many potential side effects and poor patient compliance. In this work, a 3D bioprinter was used to prepare polycaprolactone (PCL) implants loaded with TA. Implants were manufactured with different shapes (filament-, rectangular-, and circle-shaped) and drug loadings (5, 10, and 20%). The characterisation results showed that TA was successfully mixed and incorporated within the PCL matrix without using solvents, and drug content reached almost 100% for all formulations. The drug release data demonstrate that the filament-shaped implants (SA/V ratio~7.3) showed the highest cumulative drug release amongst all implant shapes over 180 days, followed by rectangular- (SA/V ratio~3.7) and circle-shaped implants (SA/V ratio~2.80). Most implant drug release data best fit the Korsmeyer−Peppas model, indicating that diffusion was the prominent release mechanism. Additionally, a biocompatibility study was performed; the results showed >90% cell viability, thus proving that the TA-loaded PCL implants were safe for ocular application.

Preparation of Isopropyl Acrylamide Grafted Chitosan and Carbon Bionanocomposites for Adsorption of Lead Ion and Methylene Blue

Wastewater, which is rich with heavy elements, dyes, and pesticides, represents one of the most important environmental pollutants. Thus, it has been significant to fabricate environmentally friendly polymers with high adsorption ability for those pollutants. Herein, crosslinked chitosan (C-Cs) was prepared using isopropyl acrylamide and methylene bisacrylamide. Carbon nanoparticles (C-NPs) were also obtained by the treatment of the agricultural wastes, which was used with C-Cs to prepare C-Cs/C-NPs nanocomposite (C-Cs/C-NC). Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscope (TEM) were used to investigate the prepared adsorbent. C-Cs, C-NPs, and C-Cs/C-NC were used in water treatment for the adsorption of lead ions (Pb⁺²) and methylene blue (MB). The adsorption process occurred by the prepared samples was investigated under different conditions, including contact time, as well as different doses and concentrations of adsorbents. The findings exhibited that the adsorption of Pb⁺² and MB by C-Cs/C-NC was higher than C-Cs and C-NPs. In addition, the kinetic and isotherm models were studied, where the results showed that the adsorption of Pb⁺² and MB by various adsorbents obeys pseudo-second-order and Langmuir isotherms, respectively.

Cefazolin Loaded Oxidized Regenerated Cellulose/Polycaprolactone Bilayered Composite for Use as Potential Antibacterial Dural Substitute

Oxidized regenerated cellulose/polycaprolactone bilayered composite (ORC/PCL bilayered composite) was investigated for use as an antibacterial dural substitute. Cefazolin at the concentrations of 25, 50, 75 and 100 mg/mL was loaded in the ORC/PCL bilayered composite. Microstructure, density, thickness, tensile properties, cefazolin loading content, cefazolin releasing profile and antibacterial activity against S. aureus were measured. It was seen that the change in concentration of cefazolin loading affected the microstructure of the composite on the rough side, but not on the dense or smooth side. Cefazolin loaded ORC/PCL bilayered composite showed greater densities, but lower thickness, compared to those of drug unloaded composite. Tensile modulus was found to be greater and increased with increasing cefazolin loading, but tensile strength and strain at break were lower compared to the drug unloaded composite. In vitro cefazolin release in artificial cerebrospinal fluid (aCSF) consisted of initial burst release on day 1, followed by a constant small release of cefazolin. The antibacterial activity was observed to last for up to 4 days depending on the cefazolin loading. All these results suggested that ORC/PCL bilayered composite could be modified to serve as an antibiotic carrier for potential use as an antibacterial synthetic dura mater.

Piperine-loaded electrospun nanofibers, an implantable anticancer controlled delivery system for postsurgical breast cancer treatment

Tumorectomy followed by radiotherapy, hormone, and chemotherapy, are the current mainstays for breast cancer treatment. However, these strategies have systemic toxicities and limited treatment outcomes. Hence, there is a crucial need for a novel controlled release delivery system for implantation following tumor resection to effectively prevent recurrence. Here, we fabricated polycaprolactone (PCL)-based electrospun nanofibers containing piperine (PIP), known for chemopreventive and anticancer activities, and also evaluated the impact of collagen (Coll) incorporation into the matrices. In addition to physicochemical characterization such as morphology, hydrophilicity, drug content, release properties, and mechanical behaviors, fabricated nanofibers were investigated in terms of cytotoxicity and involved mechanisms in MCF-7 and 4T1 breast tumor cell lines. In vivo antitumor study was performed in 4T1 tumor-bearing mice. PIP-PCL⁷⁵-Coll²⁵ nanofiber was chosen as the optimum formulation due to sustained PIP release, good mechanical performance, and superior cytotoxicity. Demonstrating no organ toxicity, animal studies confirmed the superiority of locally administered PIP-PCL⁷⁵-Coll²⁵ nanofiber in terms of inhibition of growth tumor, induction of apoptosis, and reduction of cell proliferation compared to PIP suspension, blank nanofiber, and the control. Taken together, we concluded that PIP-loaded nanofibers can be introduced as a promising treatment for implantation upon breast tumorectomy.

Advancement of Nanofibrous Mats and Common Useful Drug Delivery Applications

Electrospinning enables simple and cost-effective production of polymer nanofibers from different polymer materials. Drug delivery systems are capable of achieving maximum drug treatment benefits by significantly reducing adverse complications. Electrospun nanofibers have recently attracted considerable attention owing to their distinctive properties, including flexibility and biocompatibility. The implementation of functional constituents within nanostructure fibers blends is an effective technique for the administration of a variety of drugs in animal research, broadening the nanofiber capability and reliability. The nanofibrous mesh and its various application purposes are discussed in terms of a summary of recent research, emphasizing the ease of streaming and a large number of combinations of this approach, which could lead to a breakthrough in targeted therapy.

Ibuprofen-Loaded Electrospun PCL/PEG Nanofibrous Membranes for Preventing Postoperative Abdominal Adhesion

Electrospun nanofibrous membranes are a widely used physical barrier for reducing postoperative adhesion. However, these physical barriers could not prevent adhesion formation completely. Because a high-intensity inflammation occurs in the surgical area, the presence of relevant drugs to control such an inflammation is desperately needed. In this study, we fabricated an electrospun composite ibuprofen-loaded poly(ethylene glycol) (PEG)/polycaprolactone (PCL) nanofibrous membrane (NFM) to prevent abdominal adhesions. This membrane aimed to act as a barrier between the abdominal wall and surrounding tissues, without interrupting mass transfer and normal wound healing. Among various fabricated composite NFMs, PCL/25PEG-6% NFMs showed the lowest fiber diameter (448.8 ± 124.4 nm), the smallest pore size (<2 μm), and moderate ultimate stress and strain. The PCL/25PEG-6% NFMs had the lowest water contact angle (≈75°) and the highest drug profile release (≈80%) within 14 days. Furthermore, in vitro toxicity examination of PCL/25PEG-6% toward fibroblast cells demonstrated a cell viability of ≈82% after 3 days, proving its prolonged antiadhesion ability. In addition, the low number of adherent cells with a rounded shape and low cell proliferation on these NFMs indicated their special antiadhesive effects. Collectively, these results indicated that the PCL/25PEG-6% membrane might be a suitable barrier to prevent abdominal adhesion.

Development of an Electrospun Patch Platform Technology for the Delivery of Carvedilol in the Oral Mucosa

The work herein presented aims to develop and characterize carvedilol (CVD) releasable non-water-soluble monolayers and a multilayer patch made of ultrathin micron and submicron fibers for drug delivery into the sublingual mucosa. Firstly, the developed formulations containing CVD within different biopolymers (PDLA, PCL, and PHB) were characterized by scanning electron microscopy (SEM), attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), and for their in vitro drug release. SEM micrographs assessed the fiber morphology attained by adding carvedilol. ATR-FTIR spectra revealed good chemical compatibility between CVD and the tested biopolymers, whereas DSC and WAXS confirmed that CVD was in an amorphous state within the biopolymeric fibers. In vitro release studies showed enhanced CVD release kinetics from the electrospun biopolymer monolayers compared to the dissolution rate of the commercial form of the pure drug, except for the slow-releasing PDLA fibers. Finally, the selected CVD-loaded layer, i.e., electrospun PHB, was built into a three-layer patch to tackle mucosa adhesion and unidirectional release, while retaining the enhanced release kinetics. The patch design proposed here further demonstrates the potential of the electro-hydrodynamic processing technology to render unique mucoadhesive controlled delivery platforms for poorly water-soluble drugs.

Curcumin polymeric membranes for postoperative peritoneal adhesion: Comparison of nanofiber vs. film and phospholipid-enriched vs. non-enriched formulations

Intra-abdominal adhesion remains a major postoperative problem and is able to place individuals at lifelong risk of serious complications. Among available approaches, insertion of a barrier membrane at the site of injury partially inhibited adhesion formation. Moreover, the local administration of an anti-adhesive agent showed some favorable effects. In this study, we aimed to prepare and fully characterize polycaprolactone (PCL)-based film casts and electrospun nanofibers (NFs) containing a natural anti-inflammatory agent, curcumin (CUR), with extended-release properties. We also compared their efficiencies in preventing tissue adhesions. Additionally, the impact of soy phosphatidylcholine (SPC) enrichment on adhesion prevention was investigated. Prepared membranes were evaluated in terms of surface morphology (SEM, AFM), surface wettability, CUR release profiles, structural properties (FTIR, XRD, DSC), and mechanical behaviors. To further analyze the anti-adhesion effectiveness, a cecal abrasion model was performed on rats. SEM and AFM images showed a smoother surface in SPC-containing films. Concerning NFs, uniform bead-free fibers were observed and SPC containing NFs showed higher conductivity and lower viscosity and therefore, smaller fibers. All formulations exhibited sustained drug release over 4 weeks. In vivo findings revealed the superior performance of films compared to NFs and phospholipid-enriched formulations over non-enriched ones. Among all film formulations and in comparison to the positive control (Seprafilm®), CUR-SPC-PCL films significantly reduced peritoneal adhesions, as evidenced by gross examination, histological evaluation and immunohistochemical (IHC) analysis. The remarkable in vivo anti-adhesion activity together with suitable in vitro properties have made CUR-SPC-PCL films a promising system for postoperative anti-adhesion purposes in the clinic.

Research progress, models and simulation of electrospinning technology: a review

In recent years, nanomaterials have aroused extensive research interest in the world's material science community. Electrospinning has the advantages of wide range of available raw materials, simple process, small fiber diameter and high porosity. Electrospinning as a nanomaterial preparation technology with obvious advantages has been studied, such as its influencing parameters, physical models and computer simulation. In this review, the influencing parameters, simulation and models of electrospinning technology are summarized. In addition, the progresses in applications of the technology in biomedicine, energy and catalysis are reported. This technology has many applications in many fields, such as electrospun polymers in various aspects of biomedical engineering. The latest achievements in recent years are summarized, and the existing problems and development trends are analyzed and discussed.

Nano Iron Oxide-PCL Composite as an Improved Soft Tissue Scaffold

Iron oxide nanoparticles were employed to fabricate a soft tissue scaffold with enhanced physicochemical and biological characteristics. Growth promotion effect of L-lysine coated magnetite (Lys@Fe3O4) nanoparticles on the liver cell lines was proved previously. So, in the current experiment these nanoparticles were employed to fabricate a soft tissue scaffold with growth promoting effect on the liver cells. Lys@Fe3O4 nanoparticles were synthesized via co-precipitation reaction. Resulted particles were ~7 nm in diameter and various concentrations (3, 5, and 10 wt%) of these nanoparticles were used to fabricate nanocomposite PCL fibers. Electrospinning technique was employed and physicochemical characteristics of the resulted nanofibers were evaluated. Electron micrographs and EDX-mapping analysis showed that nanoparticles were well dispersed in the PCL fibers and no bead structure were formed. As expected, incorporation of Lys@Fe3O4 to the PCL nanofibers resulted in a reduction in hydrophobicity of the scaffold. Nanocomposite scaffolds were shown increased tensile strength with increasing concentration of employed nanoparticles. In contrast to PCL scaffold, nearly 150% increase in the cell viability was observed after 3-days exposure to the nanocomposite scaffolds. This study indicates that incorporation of magnetite nanoparticles in the PCL fibers make them more prone to cell attachment. However, incorporated nanoparticles can provide the attached cells with valuable iron element and consequently promote the cells growth rate. Based on the results, magnetite enriched PCL nanofibers could be introduced as a scaffold to enhance the biological performance for liver tissue engineering purposes.

Electrospun wound dressings containing bioactive natural products: physico-chemical characterization and biological assessment

Background

Current research on skin tissue engineering has been focusing on novel therapies for the effective management of chronic wounds. A critical aspect is to develop matrices that promote growth and uniform distribution of cells across the wound area, and at the same time offer protection, as well as deliver drugs that help wound healing and tissue regeneration. In this context, we aimed at developing electrospun scaffolds that could serve as carriers for the bioactive natural products alkannin and shikonin (A/S).

Methods

A series of polymeric nanofibers composed of cellulose acetate (CA) or poly(ε-caprolactone) (PCL) and varying ratios of a mixture of A/S derivatives, has been successfully fabricated and their physico-chemical and biological properties have been explored.

Results

Scanning electron microscopy revealed a uniform and bead-free morphology for CA scaffolds, while for PCL beads along the fibers were observed. The average diameters for all nanofibers ranged between 361 ± 47 and 487 ± 88 nm. During the assessment of physicochemical characteristics, CA fiber mats exhibited a more favored profile, while the assessment of the biological properties of the scaffolds showed that CA samples containing A/S mixture up to 1 wt.% achieved to facilitate attachment, survival and migration of Hs27 fibroblasts. With respect to the antimicrobial properties of the scaffolds, higher drug-loaded (1 and 5 wt.%) samples succeeded in inhibiting the growth of Staphylococcus epidermidis and S. aureus around the edges of the fiber mats. Finally, carrying out a structure-activity relationship study regarding the biological activities (fibroblast toxicity/proliferation and antibacterial activity) of pure A/S compounds – present in the A/S mixture – we concluded that A/S ester derivatives and the dimeric A/S augmented cell proliferation after 3 days, whereas shikonin proved to be toxic at 500 nM and 1 μM and alkannin only at 1 μM. Additionally, alkannin, shikonin and acetyl-shikonin showed more pronounced antibacterial properties than the other esters, the dimeric derivative and the A/S mixture itself.

Conclusions

Taken together, these findings indicate that embedding A/S derivatives into CA nanofibers might be an advantageous drug delivery system that could also serve as a potential candidate for biomedical applications in the field of skin tissue engineering.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40824-021-00223-9.

Electrospinning for drug delivery applications: A review

Drug delivery devices are promising tools in the pharmaceutical field, as they are able to maximize the therapeutic effects of the delivered drug while minimizing the undesired side effects. In the past years, electrospun nanofibers attracted rising attention due to their unique features, like biocompatibility and broad flexibility. Incorporation of active principles in nanofibrous meshes proved to be an efficient method for in situ delivery of a wide range of drugs, expanding the possibility and applicability of those devices. In this review, the principle of electrospinning and different fields of applications are treated to give an overview of the recent literature, underlining the easy tuning and endless combination of this technique, that in the future could be the new frontier of personalized medicine.

Long-acting implantable dosage forms containing paliperidone palmitate obtained by 3D printing

In this work, the versatility of pressure extrusion-based printing (PEBP) was used as 3D printing process to create long-acting implantable dosage forms. Different release profiles were achieved based on the drug concentration, the way of preparation and the design of the final implants. Polycaprolactone (PCL) was used as the polymer to sustain the release of the loaded drug. Paliperidone palmitate (PP), a BCS Class II drug, used in the treatment of schizophrenia, was used as the model drug. Two PP concentrations (e.g. 5 and 10% w/w) as well as two methods of preparation before the 3D printing process, mortar and pestle and cryogenic milling, were evaluated. The amorphous state of PP was obtained by using cryogenic milling and it was maintained after printing. Two designs were printed by PEBP, a ring and a disk, to evaluate their impact on the release profile of PP. During the in vitro dissolution tests, the implant design, the amount of PP, as well as the crystalline or amorphous state of PP have shown to influence the drug release profile. During the successive steps of preparation of the long-acting implants, blends and raw materials were characterized by DSC and XRD.

Electrospun poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) nanofibers for the controlled release of cilostazol

Drug delivery devices are attractive alternatives to drugs usually orally administrated. Therefore, this work aimed to produce PLA/PBAT-based nanofibers for the controlled release of cilostazol, evaluating the effect of different drug concentrations (20 and 30%) over the properties of the fibers. The fibers were characterized by scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), x-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric (TG/DTG), and mechanical analysis. SEM results indicated a high concentration of drug crystals on the surface of the fibers that contained 20% of cilostazol. These fibers were also thinner, more crystalline, less thermally stable, and less fragile in comparison to the fibers containing 30% of cilostazol, according to the XRD, DSC, TG/DTG, and mechanical results. The controlled release assays indicated that the fibers containing 20% of cilostazol would be attractive for short-term releases, reaching the equilibrium after approximately 6 h, while the ones containing 30% would ensure a slower release (~ 12 h). Despite the differences, both fibers would improve and enhance the efficiency of the treatment, and they would also prevent possible side effects caused by the drug to the gastric system.

3D printed polymeric drug-eluting implants

An extrusion-based 3D printer has been used for the manufacturing of sustained drug release poly(ε-caprolactone) (PCL) implants. Such implants can address issues of reduced patient compliance due to the necessary frequent administration of conventional drug delivery systems, such as tablets, capsules and solutions. The selected model drug for this study was lidocaine. Polycaprolactone core-shell implants, as well as polymeric implants with no barrier shell were printed with different drug loading, without the addition of solvents or further excipients. Scanning Electron Microscopy (SEM) analysis revealed the structural integrity of the printed formulations, while Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD) and Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR) were used to detect potential chemical interactions or modifications. Raman spectroscopy was also used to study material distribution in the prints. The drug release rate of the differently printed formulations was evaluated using a USP4 flow-through cell apparatus. All printed implants demonstrated sustained lidocaine release and the effectiveness of the PCL barrier in this regard. The Korsmeyer-Peppas model was suggested as the best fit to drug release profiles for all the produced implants. This work demonstrates that hot-melt extrusion-based 3D printing is a robust and promising technology for the production of personalisable drug-eluting implants.

S-Nitrosoglutathione-Based Nitric Oxide-Releasing Nanofibers Exhibit Dual Antimicrobial and Antithrombotic Activity for Biomedical Applications

The novel use of nanofibers as a physical barrier between blood and medical devices has allowed for modifiable, innovative surface coatings on devices ordinarily plagued by thrombosis, delayed healing, and chronic infection. In this study, the nitric oxide (NO) donor S-nitrosoglutathione (GSNO) is blended with the biodegradable polymers polyhydroxybutyrate (PHB) and polylactic acid (PLA) for the fabrication of hemocompatible, antibacterial nanofibers tailored for blood-contacting applications. Stress/strain behavior of different concentrations of PHB and PLA is recorded to optimize the mechanical properties of the nanofibers. Nanofibers incorporated with different concentrations of GSNO (10, 15, 20 wt%) are evaluated based on their NO-releasing kinetics. PLA/PHB + 20 wt% GSNO nanofibers display the greatest NO release over 72 h (0.4-1.5 × 10-10  mol mg-1 min-1 ). NO-releasing fibers successfully reduce viable adhered bacterial counts by ≈80% after 24 h of exposure to Staphylococcus aureus. NO-releasing nanofibers exposed to porcine plasma reduce platelet adhesion by 64.6% compared to control nanofibers. The nanofibers are found noncytotoxic (>95% viability) toward NIH/3T3 mouse fibroblasts, and 4',6-diamidino-2-phenylindole and phalloidin staining shows that fibroblasts cultured on NO-releasing fibers have improved cellular adhesion and functionality. Therefore, these novel NO-releasing nanofibers provide a safe antimicrobial and hemocompatible coating for blood-contacting medical devices.

Fabrication of Gelatin-ZnO Nanofibers for Antibacterial Applications

In this study, GNF@ZnO composites (gelatin nanofibers (GNF) with zinc oxide (ZnO) nanoparticles (NPs)) as a novel antibacterial agent were obtained using a wet chemistry approach. The physicochemical characterization of ZnO nanoparticles (NPs) and GNF@ZnO composites, as well as the evaluation of their antibacterial activity toward Gram-positive (Staphyloccocus aureus and Bacillus pumilus) and Gram-negative (Escherichia coli and Pseudomonas fluorescens) bacteria were performed. ZnO NPs were synthesized using a facile sol-gel approach. Gelatin nanofibers (GNF) were obtained by an electrospinning technique. GNF@ZnO composites were obtained by adding previously produced GNF into a Zn2+ methanol solution during ZnO NPs synthesis. Crystal structure, phase, and elemental compositions, morphology, as well as photoluminescent properties of pristine ZnO NPs, pristine GNF, and GNF@ZnO composites were characterized using powder X-ray diffraction (XRD), FTIR analysis, transmission and scanning electron microscopies (TEM/SEM), and photoluminescence spectroscopy. SEM, EDX, as well as FTIR analyses, confirmed the adsorption of ZnO NPs on the GNF surface. The pristine ZnO NPs were highly crystalline and monodispersed with a size of approximately 7 nm and had a high surface area (83 m2/g). The thickness of the pristine gelatin nanofiber was around 1 µm. The antibacterial properties of GNF@ZnO composites were investigated by a disk diffusion assay on agar plates. Results show that both pristine ZnO NPs and their GNF-based composites have the strongest antibacterial properties against Pseudomonas fluorescence and Staphylococcus aureus, with the zone of inhibition above 10 mm. Right behind them is Escherichia coli with slightly less inhibition of bacterial growth. These properties of GNF@ZnO composites suggest their suitability for a range of antimicrobial uses, such as in the food industry or in biomedical applications.

Fabrication of tri-layered electrospun polycaprolactone mats with improved sustained drug release profile

Modulation of initial burst and long term release from electrospun fibrous mats can be achieved by sandwiching the drug loaded mats between hydrophobic layers of fibrous polycaprolactone (PCL). Ibuprofen (IBU) loaded PCL fibrous mats (12% PCL-IBU) were sandwiched between fibrous polycaprolactone layers during the process of electrospinning, by varying the polymer concentrations (10% (w/v), 12% (w/v)) and volume of coat (1 ml, 2 ml) in flanking layers. Consequently, 12% PCL-IBU (without sandwich layer) showed burst release of 66.43% on day 1 and cumulative release (%) of 86.08% at the end of 62 days. Whereas, sandwich groups, especially 12% PCLSW-1 & 2 (sandwich layers-1 ml and 2 ml of 12% PCL) showed controlled initial burst and cumulative (%) release compared to 12% PCL-IBU. Moreover, crystallinity (%) and hydrophobicity of the sandwich models imparted control on ibuprofen release from fibrous mats. Further, assay for cytotoxicity and scanning electron microscopic images of cell seeded mats after 5 days showed the mats were not cytotoxic. Nuclear Magnetic Resonance spectroscopic analysis revealed weak interaction between ibuprofen and PCL in nanofibers which favors the release of ibuprofen. These data imply that concentration and volume of coat in flanking layer imparts tighter control on initial burst and long term release of ibuprofen.

Electrospun Nano-Fibers for Biomedical and Tissue Engineering Applications: A Comprehensive Review

Pharmaceutical nano-fibers have attracted widespread attention from researchers for reasons such as adaptability of the electro-spinning process and ease of production. As a flexible method for fabricating nano-fibers, electro-spinning is extensively used. An electro-spinning unit is composed of a pump or syringe, a high voltage current supplier, a metal plate collector and a spinneret. Optimization of the attained nano-fibers is undertaken through manipulation of the variables of the process and formulation, including concentration, viscosity, molecular mass, and physical phenomenon, as well as the environmental parameters including temperature and humidity. The nano-fibers achieved by electro-spinning can be utilized for drug loading. The mixing of two or more medicines can be performed via electro-spinning. Facilitation or inhibition of the burst release of a drug can be achieved by the use of the electro-spinning approach. This potential is anticipated to facilitate progression in applications of drug release modification and tissue engineering (TE). The present review aims to focus on electro-spinning, optimization parameters, pharmacological applications, biological characteristics, and in vivo analyses of the electro-spun nano-fibers. Furthermore, current developments and upcoming investigation directions are outlined for the advancement of electro-spun nano-fibers for TE. Moreover, the possible applications, complications and future developments of these nano-fibers are summarized in detail.

Electrospun Bioresorbable Membrane Eluting Chlorhexidine for Dental Implants

To prevent the uncontrolled development of a pathogenic biofilm around a dental implant, an antimicrobial drug-release electrospun membrane, set up between the implant and the gingival tissue, was developed by taking several technical, industrial and regulatory specifications into account. The membrane formulation is made of a blend of poly(l-lactic–co–gycolic acid) (PLGA, 85:15) and poly(l-lactic acide–co–ɛ-caprolactone) (PLC, 70:30) copolymers with chlorhexidine diacetate (CHX) complexed with β-cyclodextrin (CD). The amount of residual solvent, the mechanical properties and the drug release kinetics were tuned by the copolymers’ ratio, between 30% and 100% of PLC, and a CHX loading up to 20% w/w. The membranes were sterilized by γ-irradiation without significant property changes. The fiber′s diameter was between 600 nm and 3 µm, depending on the membrane composition and the electrospinning parameters. CHX was released in vitro over 10 days and the bacterial inhibitory concentration, 80 µg·mL⁻¹, was reached within eight days. The optimal membrane, PGLA/PLC/CHX-CD (60%/40%/4%), exhibited a breaking strain of 50%, allowing its safe handling. This membrane and a membrane without CHX-CD were implanted subcutaneous in a rat model. The cell penetration remained low. The next step will be to increase the porosity of the membrane to improve the dynamic cell penetration and tissue remodeling.

Regenerative medicine and drug delivery: Progress via electrospun biomaterials

Worldwide research on electrospinning enabled it as a versatile technique for producing nanofibers with specified physio-chemical characteristics suitable for diverse biomedical applications. In the case of tissue engineering and regenerative medicine, the nanofiber scaffolds' characteristics are custom designed based on the cells and tissues specific needs. This fabrication technique is also innovated for the production of nanofibers with special micro-structure and secondary structure characteristics such as porous fibers, hollow structure, and core- sheath structure. This review attempts to critically and succinctly capture the vast number of developments reported in the literature over the past two decades. We then discuss their applications as scaffolds for induction of cells growth and differentiation or as architecture for being used as graft for tissue engineering. The special nanofibers designed for improving regeneration of several tissues including heart, bone, central nerve system, spinal cord, skin and ocular tissue are introduced. We also discuss the potential of the electrospinning in drug delivery applications, which is a critical factor for cell culture, tissue formation and wound healing applications.

UV cross-linked polyvinylpyrrolidone electrospun fibres as antibacterial surfaces

Many bacteria become progressively more resistant to antibiotics and it remains a challenging task to control their overall levels. Polymers combined with active biomolecules come to the forefront for the design of antibacterial materials that can address this encounter. In this work, we investigated the photo-crosslinking approach of UV-sensitive benzophenone molecule (BP) with polyvinylpyrrolidone (PVP) polymer within electrospun fibres. The BP and PVP solutions allowed fabricating polymer mats that were subsequently functionalised with antibacterial lysozyme. The physical properties of the crosslinked electrospun fibres were investigated by scanning electron microscopy and atomic force microscopy. The average diameter of the obtained fibres decreased from 290 ± 50 nm to 270 ± 70 nm upon the addition of the crosslinking molecules and then to 240 ± 80 nm and 180 ± 90 nm after subsequent crosslinking reaction at an increasing time: 3 and 5 h, respectively. The peak force quantitative nanomechanical mapping (PF-QNM) indicated the increase of DMT modulus of obtained cross-linked fibres from 4.1 ± 0.8 GPa to 7.2 ± 0.5 GPa. Furthermore, the successful crosslinking reaction of PVP and BP solution into hydrogels was investigated in terms of examining photo-crosslinking mechanism and was confirmed by rheology, Raman, Fourier transform infrared and nuclear magnetic resonance. Finally, lysozyme was successfully encapsulated within cross-linked PVP-BP hydrogels and these were successfully electrospun into mats which were found to be as effective antibacterial agents as pure lysozyme molecules. The dissolution rate of photo cross-linked PVP mats was observed to increase in comparison to pure PVP electrospun mats which opened a potential route for their use as antibacterial, on-demand, dissolvable coatings for various biomedical applications.

Electrospun asymmetric membranes for wound dressing applications

To accomplish a rapid wound healing it is necessary to develop an asymmetric membrane with interconnected pores consisting of a top layer that prevents rapid dehydration of the wound and bacteria penetration and a sub-layer with high absorption capacity and bactericidal properties. Polycaprolactone (PCL)/polyvinyl acetate (PVAc) asymmetric membranes loaded with the bactericidal monoterpene carvacrol (CRV) were synthesized and characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. Mechanical properties in dry and wet conditions and fluid handling behavior were also assessed. In addition, biological studies regarding their bactericidal effects, cytocompatibility and wound closure properties were also developed. Loading efficiencies of 40-50% were achieved in the prepared samples and 85-100% of the loaded CRV was released in simulated wound pH evolution medium. The significant inhibition of Gram negative (Escherichia coli S17) and Gram positive (Staphylococcus aureus ATCC 25923) bacteria growth clearly showed the suitability of the fabricated membranes for wound healing applications. Furthermore, cytocompatibility of the loaded membranes was demonstrated both in 2D and 3D human dermal fibroblast cultures, as well as cell migration was not impaired by released carvacrol from the membranes. These results highlight the potential of these polymeric electrospun membranes for wound healing.

A green approach to obtain stable and hydrophilic cellulose-based electrospun nanofibrous substrates for sustained release of therapeutic molecules

Stable and (bio)-compatible nanofibrous matrices showing effective incorporation and release of nonsteroidal anti-inflammatory drugs (NSAIDs) hold a huge potential in tissue regeneration and wound healing.

Preparation and characterization of bosentan monohydrate/ε-polycaprolactone nanoparticles obtained by electrospraying

The electrospraying technique provides nano and microparticles that can be used as drug delivery systems. The aims of this study were, firstly, to optimize the influent parameters of electrospraying for the manufacture of a Bosentan (BOS) nanoparticulate platform, and secondly, to evaluate its physicochemical properties and in vitro biopharmaceutical behavior. Particles were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetry (TG) and Fourier transformed Infrared spectroscopy (FTIR). Drug loading, encapsulation efficiency and kinetic dissolution were determined. Additionally, Bosentan release assays at 24 and 72 h were performed in vitro to evaluate biopharmaceutical properties of nano-scaffolds by diffusion technique through dialysis bag. The nanostructures had heterogeneous sizes predominantly smaller than 550 nm and they were semicrystalline according to PXRD, indicating a partial amorphization of BOS during the encapsulation in the polymer matrix. FT-IR and DSC showed an absence of chemical interactions between BOS and ε-Polycaprolactone (PCL), suggesting that both components behaved as a physical mixture in these particles. The drug loading was 25.98%, and the encapsulation efficiency was 58.51%. Additionally, the release assays showed an extended and controlled release of BOS, in comparison to non-encapsulated BOS. These data also showed to fit with the Cubic Root kinetic dissolution. As a conclusion, we demonstrate that the use of electrospraying for the manufacture of BOS (or similar drugs) controlled release nanoplatforms would represent an interesting contribution in the development of new therapeutic alternatives for the treatment of pathologies such as pulmonary hypertension and other related diseases. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2748, 2019.

Building Blood Vessels with Vascular Progenitor Cells

Vascular progenitor cells have been identified from perivascular cell fractions and peripheral blood and bone marrow mononuclear fractions. These vascular progenitors share the ability to generate some of the vascular lineages, including endothelial cells, smooth muscle cells, and pericytes. The potential therapeutic uses for vascular progenitor cells are broad and relate to stroke, ischemic disease, and to the engineering of whole organs and tissues that require a vascular component. This review summarizes the best-characterized sources of vascular progenitor cells and discusses advances in 3D printing and electrospinning using blended polymers for the creation of biomimetic vascular grafts. These advances are pushing the field of regenerative medicine closer to the creation of small-diameter vascular grafts with long-term clinical utility.