Antimicrobial Activity of 3D-Printed Poly(ε-Caprolactone) (PCL) Composite Scaffolds Presenting Vancomycin-Loaded Polylactic Acid-Glycolic Acid (PLGA) Microspheres

New Generation of Osteoinductive and Antimicrobial Polycaprolactone-Based Scaffolds in Bone Tissue Engineering: A Review

With respect to other fields, bone tissue engineering has significantly expanded in recent years, leading not only to relevant advances in biomedical applications but also to innovative perspectives. Polycaprolactone (PCL), produced in the beginning of the 1930s, is a biocompatible and biodegradable polymer. Due to its mechanical and physicochemical features, as well as being easily shapeable, PCL-based constructs can be produced with different shapes and degradation kinetics. Moreover, due to various development processes, PCL can be made as 3D scaffolds or fibres for bone tissue regeneration applications. This outstanding biopolymer is versatile because it can be modified by adding agents with antimicrobial properties, not only antibiotics/antifungals, but also metal ions or natural compounds. In addition, to ameliorate its osteoproliferative features, it can be blended with calcium phosphates. This review is an overview of the current state of our recent investigation into PCL modifications designed to impair microbial adhesive capability and, in parallel, to allow eukaryotic cell viability and integration, in comparison with previous reviews and excellent research papers. Our recent results demonstrated that the developed 3D constructs had a high interconnected porosity, and the addition of biphasic calcium phosphate improved human cell attachment and proliferation. The incorporation of alternative antimicrobials-for instance, silver and essential oils-at tuneable concentrations counteracted microbial growth and biofilm formation, without affecting eukaryotic cells' viability. Notably, this challenging research area needs the multidisciplinary work of material scientists, biologists, and orthopaedic surgeons to determine the most suitable modifications on biomaterials to design favourable 3D scaffolds based on PCL for the targeted healing of damaged bone tissue.

The 3-dimensional printing for dental tissue regeneration: the state of the art and future challenges

Tooth loss or damage poses great threaten to oral and general health. While contemporary clinical treatments have enabled tooth restoration to a certain extent, achieving functional tooth regeneration remains a challenging task due to the intricate and hierarchically organized architecture of teeth. The past few decades have seen a rapid development of three-dimensional (3D) printing technology, which has provided new breakthroughs in the field of tissue engineering and regenerative dentistry. This review outlined the bioactive materials and stem/progenitor cells used in dental regeneration, summarized recent advancements in the application of 3D printing technology for tooth and tooth-supporting tissue regeneration, including dental pulp, dentin, periodontal ligament, alveolar bone and so on. It also discussed current obstacles and potential future directions, aiming to inspire innovative ideas and encourage further development in regenerative medicine.

Rising role of 3D-printing in delivery of therapeutics for infectious disease

Modern drug delivery to tackle infectious disease has drawn close to personalizing medicine for specific patient populations. Challenges include antibiotic-resistant infections, healthcare associated infections, and customizing treatments for local patient populations. Recently, 3D-printing has become a facilitator for the development of personalized pharmaceutic drug delivery systems. With a variety of manufacturing techniques, 3D-printing offers advantages in drug delivery development for controlled, fine-tuned release and platforms for different routes of administration. This review summarizes 3D-printing techniques in pharmaceutics and drug delivery focusing on treating infectious diseases, and discusses the influence of 3D-printing design considerations on drug delivery platforms targeting these diseases. Additionally, applications of 3D-printing in infectious diseases are summarized, with the goal to provide insight into how future delivery innovations may benefit from 3D-printing to address the global challenges in infectious disease.

Enhancing antioxidant delivery through 3D printing: a pathway to advanced therapeutic strategies

The rapid advancement of 3D printing has transformed industries, including medicine and pharmaceuticals. Integrating antioxidants into 3D-printed structures offers promising therapeutic strategies for enhanced antioxidant delivery. This review explores the synergistic relationship between 3D printing and antioxidants, focusing on the design and fabrication of antioxidant-loaded constructs. Incorporating antioxidants into 3D-printed matrices enables controlled release and localized delivery, improving efficacy while minimizing side effects. Customization of physical and chemical properties allows tailoring of antioxidant release kinetics, distribution, and degradation profiles. Encapsulation techniques such as direct mixing, coating, and encapsulation are discussed. Material selection, printing parameters, and post-processing methods significantly influence antioxidant release kinetics and stability. Applications include wound healing, tissue regeneration, drug delivery, and personalized medicine. This comprehensive review aims to provide insights into 3D printing-assisted antioxidant delivery systems, facilitating advancements in medicine and improved patient outcomes for oxidative stress-related disorders.

Technologies for the fabrication of crosslinked polysaccharide-based hydrogels and its role in microbial three-dimensional bioprinting - A review

Three-Dimensional bioprinting has recently gained more attraction among researchers for its wide variety of applicability. This technology involving in developing structures that mimic the natural anatomy, and also aims in developing novel biomaterials, bioinks which have a better printable ability. Different hydrogels (cross-linked polysaccharides) can be used and optimized for good adhesion and cell proliferation. Manufacturing hydrogels with adjustable characteristics allows for fine-tuning of the cellular microenvironment. Different printing technologies can be used to create hydrogels on a micro-scale which will allow regular, patterned integration of cells into hydrogels. Controlling tissue constructions' structural architecture is the important key to ensuring its function as it is designed. The designed tiny hydrogels will be useful in investigating the cellular behaviour within the environments. Three-Dimensional designs can be constructed by modifying their shape and behaviour analogous concerning pressure, heat, electricity, ultraviolet radiation or other environmental elements. Yet, its application in in vitro infection models needs more research and practical study. Microbial bioprinting has become an advancing field with promising potential to develop various biomedical as well as environmental applications. This review elucidates the properties and usage of different hydrogels for Three-Dimensional bioprinting.

Drug Loaded 3D-Printed Poly(ε-Caprolactone) Scaffolds for Local Antibacterial or Anti-Inflammatory Treatment in Bone Regeneration

Annual bone grafting surgeries due to bone fractures, resections of affected bones, skeletal anomalies, osteoporosis, etc. exceed two million worldwide. In this regard, the creation of new materials for bone tissue repair is one of the urgent tasks of modern medicine. Additive manufacturing, or 3D printing, offers great opportunities for the development of materials with diverse properties and designs. In this study, the one-pot technique for the production of 3D scaffolds based on poly(ε-caprolactone) (PCL) loaded with an antibiotic or anti-inflammatory drug was proposed. In contrast to previously described methods to prepare drug-containing scaffolds, drug-loaded PCL scaffolds were prepared by direct 3D printing from a polymer/drug blend. An investigation of the mechanical properties of 3D-printed scaffolds containing 0.5-5 wt% ciprofloxacin (CIP) or dexamethasone (DEX) showed almost no effect of the drug (compression modulus ~70-90 MPa) compared to unfilled PCL (74 MPa). At the same time, introducing the drug and increasing its content in the PCL matrix contributed to a 1.8-6.8-fold decrease in the specific surface area of the scaffold, depending on composition. The release of CIP and DEX in phosphate buffer solution and in the same buffer containing lipase revealed a faster release in enzyme-containing medium within 45 days. Furthermore, drug release was more intensive from scaffolds with a low drug load. Analysis of the release profiles using a number of mathematical dissolution models led to the conclusion that diffusion dominates over other probable factors. In vitro biological evaluation of the scaffolds containing DEX showed moderate toxicity against osteoblast-like and leukemia monocytic cells. Being 3D-printed together with PCL both drugs retain their biological activity. PCL/CIP and PCL/DEX scaffolds demonstrated antibacterial properties against Pseudomonas aeruginosa (a total inhibition after 48 h) and anti-inflammatory activity in experiments on TNFα-activated monocyte cells (a 4-time reduction in CD-54 expression relative to control), respectively.

Antimicrobial and Biodegradable 3D Printed Scaffolds for Orthopedic Infections

In bone tissue engineering, the performance of scaffolds underpins the success of the healing of bone. Microbial infection is the most challenging issue for orthopedists. The application of scaffolds for healing bone defects is prone to microbial infection. To address this challenge, scaffolds with a desirable shape and significant mechanical, physical, and biological characteristics are crucial. 3D printing of antibacterial scaffolds with suitable mechanical strength and excellent biocompatibility is an appealing strategy to surmount issues of microbial infection. The spectacular progress in developing antimicrobial scaffolds, along with beneficial mechanical and biological properties, has sparked further research for possible clinical applications. Herein, the significance of antibacterial scaffolds designed by 3D, 4D, and 5D printing technologies for bone tissue engineering is critically investigated. Materials such as antibiotics, polymers, peptides, graphene, metals/ceramics/glass, and antibacterial coatings are used to impart the antimicrobial features for the 3D scaffolds. Polymeric or metallic biodegradable and antibacterial 3D-printed scaffolds in orthopedics disclose exceptional mechanical and degradation behavior, biocompatibility, osteogenesis, and long-term antibacterial efficiency. The commercialization aspect of antibacterial 3D-printed scaffolds and technical challenges are also discussed briefly. Finally, the discussion on the unmet demands and prevailing challenges for ideal scaffold materials for fighting against bone infections is included along with a highlight of emerging strategies in this field.

Vancomycin-loaded silk fibroin microspheres in an injectable hydrogel for chronic osteomyelitis therapy

Introduction: Chronic osteomyelitis remains a clinical challenge in orthopedics. Methods: In this study, silk fibroin microspheres (SFMPs) loaded with vancomycin are entrapped in an injectable silk hydrogel to form a vancomycin delivery system for treatment of chronic osteomyelitis. Results and Discussion: Vancomycin showed continuous release from the hydrogel for up to 25 days. The hydrogel shows strong antibacterial activity against both Escherichia coli and Staphylococcus aureus and a long antibacterial duration of 10 days without a decrease in the antibacterial effect. The injection of vancomycin-loaded silk fibroin microspheres entrapped in the hydrogel into the infected site of rat tibia reduced bone infection and improved bone regeneration compared with other treatment groups. Conclusion: Thus, the composite SF hydrogel features a sustained-release profile and good biocompatibility, making it promising for application in osteomyelitis treatment.

Drug/bioactive eluting chitosan composite foams for osteochondral tissue engineering

Joint defects associated with a variety of etiologies often extend deep into the subchondral bone leading to functional impairment and joint immobility, and it is a very challenging task to regenerate the bone-cartilage interface offering significant opportunities for biomaterial-based interventions to improve the quality of life of patients. Herein drug-/bioactive-loaded porous tissue scaffolds incorporating nano-hydroxyapatite (nHAp), chitosan (CS) and either hydroxypropyl methylcellulose (HPMC) or Bombyx mori silk fibroin (SF) are fabricated through freeze drying method as subchondral bone substitute. A combination of spectroscopy and microscopy (Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), and X-ray fluorescence (XRF) were used to analyze the structure of the porous biomaterials. The compressive mechanical properties of these scaffolds are biomimetic of cancellous bone tissues and capable of releasing drugs/bioactives (exemplified with triamcinolone acetonide, TA, or transforming growth factor-β1, TGF-β1, respectively) over a period of days. Mouse preosteoblast MC3T3-E1 cells were observed to adhere and proliferate on the tissue scaffolds as confirmed by the cell attachment, live-dead assay and alamarBlue™ assay. Interestingly, RT-qPCR analysis showed that the TA downregulated inflammatory biomarkers and upregulated the bone-specific biomarkers, suggesting such tissue scaffolds have long-term potential for clinical application.

A 3D multifunctional bi-layer scaffold to regulate stem cell behaviors and promote osteochondral regeneration

Osteochondral defect (OCD) regeneration remains a great challenge. Recently, multilayer scaffold simulating native osteochondral structures have aroused broad interest in osteochondral tissue engineering. Here, we developed a 3D multifunctional bi-layer scaffold composed of a kartogenin (KGN)-loaded GelMA hydrogel (GelMA/KGN) as an upper layer mimicking a cartilage-specific extracellular matrix and a hydroxyapatite (HA)-coated 3D printed polycaprolactone porous scaffold (PCL/HA) as a lower layer simulating subchondral bone. The bi-layer scaffolds were subsequently modified with tannic acid (TA) prime-coating and E7 peptide conjugation (PCL/HA-GelMA/KGN@TA/E7) to regulate endogenous stem cell behaviors and exert antioxidant activity for enhanced osteochondral regeneration. In vitro, the scaffolds could support cell attachment and proliferation, and enhance the chondrogenic and osteogenic differentiation capacity of bone marrow-derived mesenchymal stem cells (BMSCs) in a specific layer. Besides, the incorporation of TA/E7 significantly increased the biological activity of the bi-layer scaffolds including the pro-migratory effect, antioxidant activity, and the maintenance of cell viability against oxidative stress. In vivo, the developed bi-layer scaffolds enhanced the simultaneous regeneration of cartilage and subchondral bone when implanted into a rabbit OCD model through macroscopic, micro-CT, and histological evaluation. Taken together, these investigations demonstrated that the 3D multifunctional bi-layer scaffolds could provide a suitable microenvironment for endogenous stem cells, and promote in situ osteochondral regeneration, showing great potential for the clinical treatment of OCD.

Fabrication, bacteriostasis and osteointegration properties researches of the additively-manufactured porous tantalum scaffolds loading vancomycin

Infected bone defects (IBDs) remains a challenging problem for orthopedists. Clinically, routine management for IBDs has two stages: debridement and systematic antibiotics administration to control infection, and secondary grafting to repair bone defects. Whereas the efficacy is not satisfactory, because the overuse of antibiotics may lead to systemic toxicity, and the emergence of drug-resistant bacteria, as well as the secondary surgery would cause additional trauma and economic burden to the patients. Therefore, it is imperative to develop a novel scaffold for one-stage repair of IBDs. In this study, vancomycin (Van) was encapsulated into poly(lactic co-glycolic acid) (PLGA) microspheres through the double emulsion method, which were then loaded into the additively-manufactured porous tantalum (AM-Ta) through gelatin methacryloyl (GelMA) hydrogel to produce the composite Ta/GelMA hydrogel (Gel)/PLGA/vancomycin(Van) scaffolds for repairing IBDs. Physiochemical characterization of the newly-developed scaffold indicated that the releasing duration of Van was over 2 weeks. Biological experiments indicated good biocompatibility of the composite scaffold, as well as bacteriostasis and osteointegration properties, which showed great potential for clinical application. The construction of this novel scaffold would provide new sight into the development of orthopaedic implants, shedding a novel light on the treatment of IBDs.

Current research progress of local drug delivery systems based on biodegradable polymers in treating chronic osteomyelitis

Chronic osteomyelitis is one of the most challenging diseases in orthopedic treatment. It is usually treated with intravenous antibiotics and debridement in clinical practice, which also brings systemic drug side effects and bone defects. The local drug delivery system of antibiotics has the characteristics of targeted slow release to the lesion site, replacing systemic antibiotics and reducing the toxic and side effects of drugs. It can also increase the local drug concentration, achieve sound bacteriostatic effects, and promote bone healing and formation. Currently, PMMA beads are used in treating chronic osteomyelitis at home and abroad, but the chain beads need to be removed after a second operation, inconveniences patients. Biodegradable materials have been extensively studied as optimal options for antibiotic encapsulation and delivery, bringing new hope for treating chronic osteomyelitis. This article reviews the research progress of local drug delivery systems based on biodegradable polymers, including natural and synthetic ones, in treating chronic osteomyelitis.

The Influence of Graphene Content on the Antibacterial Properties of Polycaprolactone

This work contains an analysis of the impact of modifying a bioresorbable polymer—polycaprolactone (PCL)—with various additives on its antibacterial properties. To this end, samples of PCL filament containing various content levels of graphene (GNP), 0.5%, 5%, 10%, were obtained using injection molding. Polymer samples without additives were used for comparison. The next step was to assess the antimicrobial impact of the preparations under study against the following microorganisms: Staphylococcus aureus ATCC 25293, Escherichia coli ATCC 25922, Candida albicans ATCC 10231. Effective bactericidal activity of PCL with small amount of GNP, especially against C. albicans and S. aureus was confirmed. A decrease in this property or even multiplication of microorganisms was observed in direct proportion to the graphene content in the samples.

Computer-aided patterning of PCL microspheres to build modular scaffolds featuring improved strength and neovascularized tissue integration

In the past decade, modular scaffolds prepared by assembling biocompatible and biodegradable building blocks (e.g. microspheres) have found promising applications in tissue engineering (TE) towards the repair/regeneration of damaged and impaired tissues. Nevertheless, to date this approach has failed to be transferred to the clinic due to technological limitations regarding microspheres patterning, a crucial issue for the control of scaffold strength, vascularization and integration in vivo. In this work, we propose a robust and reliable approach to address this issue through the fabrication of polycaprolactone (PCL) microsphere-based scaffolds with in-silico designed microarchitectures and high compression moduli. The scaffold fabrication technique consists of four main steps, starting with the manufacture of uniform PCL microspheres by fluidic emulsion technique. In the second step, patterned polydimethylsiloxane (PDMS) moulds were prepared by soft lithography. Then, layers of 500 µm PCL microspheres with geometrically inspired patterns were obtained by casting the microspheres onto PDMS moulds followed by their thermal sintering. Finally, three-dimensional porous scaffolds were built by the alignment, stacking and sintering of multiple (up to six) layers. The so prepared scaffolds showed excellent morphological and microstructural fidelity with respect to the in-silico models, and mechanical compression properties suitable for load bearing TE applications. Designed porosity and pore size features enabled in vitro human endothelial cells adhesion and growth as well as tissue integration and blood vessels invasion in vivo. Our results highlighted the strong impact of spatial patterning of microspheres on modular scaffolds response, and pay the way about the possibility to fabricate in silico-designed structures featuring biomimetic composition and architectures for specific TE purposes.

Controlling the Spatiotemporal Release of Nerve Growth Factor by Chitosan/Polycaprolactone Conduits for Use in Peripheral Nerve Regeneration

Tubular polymeric structures have been recognized in the treatment of peripheral nerves as comparable to autologous grafting. The best therapeutic outcomes are obtained with conduits releasing therapeutic molecules. In this study, a new approach for the incorporation of biologically active agent-loaded microspheres into the structure of chitosan/polycaprolactone conduits was developed. The support of a polycaprolactone helix formed by 3D melt extrusion was coated with dopamine in order to adsorb nerve growth factor-loaded microspheres. The complex analysis of the influence of process factors on the coverage efficiency of polycaprolactone helix by nerve grow factor-loaded microspheres was analyzed. Thus, the PCL helix characterized with the highest adsorption of microspheres was subjected to nerve growth factor release studies, and finally incorporated into chitosan hydrogel deposit through the process of electrophoretic deposition. It was demonstrated by chemical and physical tests that the chitosan/polycaprolactone conduit meets the requirements imposed on peripheral nerve implants, particularly mimicking mechanical properties of surrounding soft tissue. Moreover, the conduit may support regrowing nerves for a prolonged period, as its structure and integrity persist upon incubation in lysozyme-contained PBS solution up to 28 days at body temperature. In vitro cytocompatibility toward mHippoE-18 embryonic hippocampal cells of the chitosan/polycaprolactone conduit was proven. Most importantly, the developed conduits stimulate axonal growth and support monocyte activation, the latter is advantageous especially at early stages of nerve regeneration. It was demonstrated that, through the described approach for controlling spatiotemporal release of nerve growth factors, these biocompatible structures adjusted to the specific peripheral nerve injury case can be manufactured.

Nanocarrier-hydrogel composite delivery systems for precision drug release

Hydrogels are a class of biomaterials widely implemented in medical applications due to their biocompatibility and biodegradability. Despite the many successes of hydrogel-based delivery systems, there remain challenges to hydrogel drug delivery such as a burst release at the time of administration, a limited ability to encapsulate certain types of drugs (i.e., hydrophobic drugs, proteins, antibodies, and nucleic acids), and poor tunability of geometry and shape for controlled drug release. This review discusses two main important advances in hydrogel fabrication for precision drug release: first, the incorporation of nanocarriers to diversify their drug loading capability, and second, the design of hydrogels using 3D printing to precisely control drug dosing and release kinetics via high-resolution structures and geometries. We also outline ongoing challenges and discuss opportunities to further optimize drug release from hydrogels for personalized medicine. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Lactobacillus amylovorus derived lipase-mediated silver derivatization over poly(ε-caprolactone) towards antimicrobial coatings

Owing to the probiotic origin, lipases-derived from the Lactobacilli sp. are considered to be promising biomaterials for in vivo applications. On a different note, poly(ε-caprolactone) (PCL)-an FDA-approved polymer for implantable applications-lacks inherent antimicrobial property, because of which suitable modifications are required to render it with bactericidal activity. Here, we employ Lactobacillus amylovorous derived lipase to surface derivatize the PCL films with silver that is a highly efficient inorganic broad-spectrum antimicrobial substance. Two different surface functionalization strategies have been employed over the alkaline hydrolyzed PCL films towards this purpose: In the first strategy, lipase-capped silver nanoparticles (Ag NPs) have been synthesized in a first step, which have been covalently immobilized over the activated carboxylic groups on the PCL film surface in a subsequent step. In the second strategy, the lipase was covalently immobilized over the activated carboxylic groups of the PCL film surface in the first step, over which silver was deposited in the second step using the dip-coating method. While the characterization study using X-ray photoelectron spectroscopy (XPS) has revealed the successful derivatization of silver over the PCL film, the surface characterization using field-emission scanning electron microscopy (FE-SEM) study has shown a distinct morphological change with higher silver loading in both strategies. The antimicrobial studies employing E. coli have revealed 100 % inhibition in the bacterial growth in 4-6 h with the Ag NPs-immobilized PCL films as opposed to >8 h with those prepared through the dip-coating method. Additionally, the cytotoxicity assay using mouse fibroblast cells has shown that the PCL films immobilized with lipase-capped Ag NPs exhibit high cell compatibility, similar to that of pristine PCL film, and thereby making it suitable for in vivo applications.

IGF-1-releasing PLGA nanoparticles modified 3D printed PCL scaffolds for cartilage tissue engineering

The aim of this study is to fabricate and test a 3D-printed PCL scaffold incorporating IGF-1-releasing PLGA nanoparticles for cartilage tissue engineering. IGF-1 loaded PLGA nanoparticles were produced by the double-emulsion method, and were incorporated onto 3D printed PCL scaffolds via PDA. Particle size, loading effciency (LE) and encapsulation effciency (EE) of the nanoparticles were examined. SEM, pore size, porosity, compression testing, contact angle, IGF-1 release kinetics of the composite scaffolds were also determined. For cell culture studies, CCK-8, Live/dead, MTT, GAG content and expression level of chondrocytes specific proteins and genes and HIF-1α were also tested. There was no difference of the nanoparticle size. And the LE and EE of IGF-1 in PLGA nanoparticles was about 5.53 ± 0.12% and 61.26 ± 2.71%, respectively. There was a slower, sustained release for all drug-loaded nanoparticles PLGA/PDA/PCL scaffolds. There was no difference of pore size, porosity, compressive strength of each scaffold. The contact angles PCL scaffolds were significant decreased when coated with PDA and PLGA nanoparticales. (p < .05) Live/dead staining showed more cells attached to the IGF-1 PLGA/PDA/PCL scaffolds. The CCK-8 and MTT assay showed higher cell proliferation and better biocompatibility of the IGF-1 PLGA/PDA/PCL scaffolds. (p < .05) GAG content, chondrogenic protein and gene expression level of SOX-9, COL-II, ACAN, and HIF pathway related gene (HIF-1α) were significantly higher in IGF-1 PLGA/PDA/PCL scaffolds group compared to other groups. (p < .05) IGF-1 PLGA/PDA/PCL scaffolds may be a better method for sustained IGF-1 administration and a promising scaffold for cartilage tissue engineering.

Tumor necrosis factor-α small interfering RNA alveolar epithelial cell-targeting nanoparticles reduce lung injury in C57BL/6J mice with sepsis

Background

The role of tumor necrosis factor (TNF)-α small interfering (si)RNA alveolar epithelial cell (AEC)-targeting nanoparticles in lung injury is unclear.

Methods

Sixty C57BL/6J mice with sepsis were divided into normal, control, sham, 25 mg/kg, 50 mg/kg, and 100 mg/kg siRNA AEC-targeting nanoparticles groups (n = 10 per group). The wet:dry lung weight ratio, and hematoxylin and eosin staining, western blotting, and enzyme-linked immunosorbent assays for inflammatory factors were conducted to compare differences among groups.

Results

The wet:dry ratio was significantly lower in control and sham groups than other groups. TNF-α siRNA AEC-targeting nanoparticles significantly reduced the number of eosinophils, with significantly lower numbers in the 50 mg/kg group than in 25 mg/kg and 100 mg/kg groups. The nanoparticles also significantly reduced the expression of TNF-α, B-cell lymphoma-2, caspase 3, interleukin (IL)-1β, and IL-6, with TNF-α expression being significantly lower in the 50 mg/kg group than in 25 mg/kg and 100 mg/kg groups.

Conclusion

TNF-α siRNA AEC-targeting nanoparticles appear to be effective at improving lung injury-related sepsis, and 50 mg/kg may be a preferred dose option for administration.

Imminent antimicrobial bioink deploying cellulose, alginate, EPS and synthetic polymers for 3D bioprinting of tissue constructs

3D printing, one of its kinds has been a recent technological trend to fabricate complex and patterned biomaterial with controlled precision. With the conventional kick-start of printing metals and plastics, advancements in printing viable cells, polysaccharides or microbes themselves have been achieved. The additive antimicrobial properties in bioinks sourced from organic and inorganic materials have profound implications in tissue engineering. Cellulose, alginate, exopolysaccharides, ceramics and synthetic polymers are integrated as a viable component in inks and used for bio-printing. To date, bacterial infection and immunogenicity pose a potential health risk during a tissue implant or bone substitution. In order to mitigate microbial infection, antimicrobial bioinks with significant antimicrobial potential have been the much sought after strategies. This approach could be an effective frontline defense against microbial interference in tissue engineering and biomedical applications. An overview on the antimicrobial potential of polysaccharides as bioinks for 3D bioprinting has been critically reviewed.

Development and Biocompatibility Analysis of NBD Peptide Sustained- Release Microsphere Scaffold Nanoparticle SP-Sr-CaS/NBD

BACKGROUND

In clinical treatment, it is difficult to carry out effective bone tissue transplantation and anti-inflammatory treatment at the same time due to bone defects and osteomyelitis where the tissue is contaminated or infected. As a downstream target of TNF-α, NF-κB has an inhibition effect on the proliferation and differentiation of cells surrounding the lesion. As a negative effect, it leads to a reduction in bone growth and development.

METHODS

In this study, the small molecule NBD polypeptide and bone conduction matrix Sr-CaS are microspheres, formed to prepare Sr-CaS, NBD drug-loaded sustained-release microspheres in order to achieve a Sr-CaS/NBD peptide drug-loaded sustained release microsphere scaffold material (SP-Sr-CaS/NBD). We prepared the microspheres and optimized the production process to obtain particles with stable morphological properties and sustained release properties.

RESULT

In vitro experiments demonstrated that SP-Sr-CaS/NBD could reduce TNF-α-induced cell growth inhibition, caspase-3 activity and NF-κB transcriptional activation as the function of continuous NBD peptide dosing regimen.

CONCLUSION

Also, the introduction of the Sr-CaS matrix potentiates microspheres to promote cell proliferation and provides a basis to become a promising 3D bone scaffold material in the future.

Development of an antimicrobial peptide-loaded mineralized collagen bone scaffold for infective bone defect repair

The repair of infective bone defects is a great challenge in clinical work. It is of vital importance to develop a kind of bone scaffold with good osteogenic properties and long-term antibacterial activity for local anti-infection and bone regeneration. A porous mineralized collagen (MC) scaffold containing poly(d,l-lactide-co-glycolic acid) (PLGA) microspheres loaded with two antibacterial synthetic peptides, Pac-525 or KSL-W was developed and characterized via scanning electron microscopy (SEM), porosity measurement, swelling and mechanical tests. The results showed that the MC scaffold embedded with smooth and compact PLGA microspheres had a positive effect on cell growth and also had antibacterial properties. Through toxicity analysis, cell morphology and proliferation analysis and alkaline phosphatase evaluation, the antibacterial scaffolds showed excellent biocompatibility and osteogenic activity. The antibacterial property evaluated with Staphylococcus aureus and Escherichia coli suggested that the sustained release of Pac-525 or KSL-W from the scaffolds could inhibit the bacterial growth aforementioned in the long term. Our results suggest that the antimicrobial peptides-loaded MC bone scaffold has good antibacterial and osteogenic activities, thus providing a great promise for the treatment of infective bone defects.

Developments in Antibiotic-Eluting Scaffolds for the Treatment of Osteomyelitis

Osteomyelitis is a devastating disease caused by the infection of bone tissue and is associated with significant morbidity and mortality. It is treated with antibiotic therapy and surgical debridement. A high dose of systemic antibiotics is often required due to poor bone penetration and this is often associated with unacceptable side-effects. To overcome this, local, implantable antibiotic carriers such as polymethyl methacrylate have been developed. However, this is a non-biodegradable material that requires a second surgery to be removed. Attention has therefore shifted to new antibiotic-eluting scaffolds which can be created with a range of unique properties. The purpose of this review is to assess the level of evidence that exists for these novel local treatments. Although this field is still developing, these strategies seem promising and provide hope for the future treatment of chronic osteomyelitis.

Encapsulation of collagen mimetic peptide-tethered vancomycin liposomes in collagen-based scaffolds for infection control in wounds

Wound infections are a significant clinical problem affecting millions of people worldwide. Topically applied antibacterial formulations with longer residence time and controlled antimicrobial release would offer significant benefits for improved prevention and treatment of infected wounds. In this study, we developed collagen mimetic peptide (CMP) tethered vancomycin (Van)-containing liposomes (Lipo) (CMP-Van-Lipo) hybridized to collagen-based hydrogels ('co-gels,' e.g., collagen/fibrin combination hydrogels) for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections in vitro and in vivo. Tethering CMP-Van-Lipo nanostructures to co-gels enabled sustained Van release and enhanced in vitro antibacterial effects against MRSA as compared to Van loaded co-gels or Van-Lipo loaded co-gels following multiple fresh bacterial inoculations over a period of 48 h. These results were successfully translated in vivo wherein MRSA infected wounds were effectively treated with CMP-Van-Lipo loaded co-gels for up to 9 days, whereas the activity of Van loaded co-gels and Van-Lipo loaded co-gels were limited to <2 days. Moreover, CMP-Van-Lipo retained in vivo antibacterial activity even after re-inoculation with bacteria; however, Van loaded co-gels and Van-Lipo loaded co-gels allowed significant bacterial growth demonstrating their limited efficacy. Altogether, these results provide proof-of-concept that CMP-Van-Lipo loaded co-gels can be effective topical formulations for preventive treatment of MRSA wound infections. STATEMENT OF SIGNIFICANCE: Current topical antimicrobial formulations (e.g., creams, gels, and ointments) do not control release, leaving antimicrobial concentrations either too high or too low at different time points, and provoking the development of antibacterial resistance and recurrence of wound infections. Here, collagen mimetic peptides (CMPs) were used to stably hybridize vancomycin-containing liposomal nanocarriers (CMP-Van-Lipo) within collagen-fibrin co-gels via triple-helical integration with collagen, enabling control over Van release for prolonged time periods and minimizing the adverse effects of the Lipo formulations on fibroblast cell viability in the wound bed. The CMP-Van-Lipo loaded co-gel's higher antibacterial effects in vitro were successfully translated in vivo for treatment of MRSA-infected mouse wounds, and thus the co-gels can be a potentially translatable treatment for improved clinical wound management.

Antibiotics in 3D-printed implants, instruments and materials: benefits, challenges and future directions

3D printing is an additive manufacturing technology, which permits innovative approaches for incorporating antibiotics into 3D printed constructs. Antibiotic-incorporating applications in medicine have included medical implants, prostheses, along with procedural and surgical instruments. 3D-printed antibiotic-impregnated devices offer the advantages of increased surface area for drug distribution, sequential layers of antibiotics produced through layer-by-layer fabrication, and the ability to rapidly fabricate constructs based on patient-specific anatomies. To date, fused deposition modeling has been the main 3D printing method used to incorporate antibiotics, although inkjet and stereolithography techniques have also been described. This review offers a state-of-the-art summary of studies that incorporate antibiotics into 3D-printed constructs and summarizes the rationale, challenges, and future directions for the potential use of this technology in patient care.

Lithium Chloride-Releasing 3D Printed Scaffold for Enhanced Cartilage Regeneration

Background

We synthetized a 3D printed poly-ɛ-caprolactone (PCL) scaffold with polydopamine (PDA) coating and lithium chloride (LiCl) deposition for cartilage tissue engineering and analyzed its effect on promoting rabbit bone marrow mesenchymal stem cells (rBMSC) chondrogenesis in vitro.

Material/Methods

PCL scaffolds were prepared by 3D printing with a well-designed CAD digital model, then modified by PDA coating to produce PCL-PDA scaffolds. Finally, LiCl was deposited on the PDA coating to produce PCL-PDA-Li scaffolds. The physicochemical properties, bioactivity, and biocompatibility of PCL-PDA-Li scaffolds were accessed by comparing them with PCL scaffolds and PCL-PDA scaffolds.

Results

3D PCL scaffolds exhibited excellent mechanical integrity as designed. PDA coating and LiCl deposition improved surface hydrophilicity without sacrificing mechanical strength. Li⁺ release was durable and ion concentration did not reach the cytotoxicity level. This in vitro study showed that, compared to PCL scaffolds, PCL-PDA and PCL-PDA-Li scaffolds significantly increased glycosaminoglycan (GAG) formation and chondrogenic marker gene expression, while PCL-PDA-Li scaffolds showed far higher rBMSC viability and chondrogenesis.

Conclusions

3D printed PCL-PDA-Li scaffolds promoted chondrogenesis in vitro and may provide a good method for lithium administration and be a potential candidate for cartilage tissue engineering.