Preparation of ciprofloxacin loaded zein conduits with good mechanical properties and antibacterial activity

Electrosprayed zein nanoparticles as antibacterial and anti-thrombotic coatings for ureteral stents

Ureteral stents are among the most frequently used human implants, with urothelium trauma, blood clots, and bacterial colonization being their main reasons for failure. In this study, berberine-loaded zein (ZB) nanoparticles with high drug encapsulation efficiency (>90 %) were fabricated via electrospray on flat and 3D stainless steel structures. Physico-chemical characterization revealed that the ZB nanoparticles created a highly hydrophilic, antioxidant, and scratch-resistant continuous coating over the metal structure. Results showed that the drug release rate was faster at neutral pH (i.e., PBS pH 7.4) than in an artificial urine medium (pH 5.3) due to the different swelling behavior of the zein polymeric matrix. In vitro evaluation of ZB particles onto human dermal fibroblasts and blood cells demonstrated good cell proliferation and enhanced anti-thrombotic properties compared to bare stainless steel. The ability of the electrosprayed zein particles to resist bacterial adherence and proliferation was evaluated with Gram-negative (Escherichia coli) bacteria, showing high inhibition rates (-29 % and -46 % for empty and berberine-loaded particles, respectively) compared to the medical-grade metal substrates. Overall, the proposed composite coating fulfilled the requirements for ureteral applications, and can advance the development of innovative biocompatible, biodegradable, and antibacterial coatings for drug-eluting stents.

Zein nanospheres assisting inorganic and organic drug combination to overcome stent implantation-induced thrombosis and infection

The complication of stent implantation is the biggest obstacle to the success of its clinical application. In this study, we developed a combination way of 3D printing and the coating technique for preparation of functional polyurethane stents against stent implantation-induced thrombosis and postoperative infection. SEM, XPS, static water contact angle, and XRD demonstrated that the functional polyurethane stent had a 37 μm-thickness membrane composed of zein nanospheres (250-350 nm). Meanwhile, ZnO nanoparticles were encapsulated in zein nanospheres while heparin was adsorbed on the surface, causing 97.1 ± 6.4 % release of heparin in 120 min (first-order kinetic model) and 62.7 ± 5.6 % release of Zn²⁺ in 9 days (Korsmeyer-Peppas model). The mechanical analysis revealed that the functional polyurethane stents had about 8.61 MPa and 2.5 MPa tensile strength and bending strength, respectively. The in vitro biological analysis showed that the functional polyurethane stents had good EA.hy926 cells compatibility (97.9 ± 3.8 %), anti-coagulation response (comparable plasma protein, platelet adhesion and suppressed clotting) and sustained antibacterial activities by comparison with the bare polyurethane stent. The preliminary evaluation by rabbit ex vivo carotid artery intervention experiment demonstrated that the functional polyurethane stents could maintain blood circulation under the continuous stresses of blood flow. Meanwhile, the detailed data from the simulated implant infection experiment in vivo showed the functional polyurethane stents could effectively reduce microbial infection by 3-6 times lower and improve fibrosis and macrophage infiltration.

Bacterial Cellulose-Based Materials: A Perspective on Cardiovascular Tissue Engineering Applications

Today, a wide variety of bio- and nanomaterials have been deployed for cardiovascular tissue engineering (TE), including polymers, metal oxides, graphene/its derivatives, organometallic complexes/composites based on inorganic-organic components, among others. Despite several advantages of these materials with unique mechanical, biological, and electrical properties, some challenges still remain pertaining to their biocompatibility, cytocompatibility, and possible risk factors (e.g., teratogenicity or carcinogenicity), restricting their future clinical applications. Natural polysaccharide- and protein-based (nano)structures with the benefits of biocompatibility, sustainability, biodegradability, and versatility have been exploited in the field of cardiovascular TE focusing on targeted drug delivery, vascular grafts, engineered cardiac muscle, etc. The usage of these natural biomaterials and their residues offers several advantages in terms of environmental aspects such as alleviating emission of greenhouse gases as well as the production of energy as a biomass consumption output. In TE, the development of biodegradable and biocompatible scaffolds with potentially three-dimensional structures, high porosity, and suitable cellular attachment/adhesion still needs to be comprehensively studied. In this context, bacterial cellulose (BC) with high purity, porosity, crystallinity, unique mechanical properties, biocompatibility, high water retention, and excellent elasticity can be considered as promising candidate for cardiovascular TE. However, several challenges/limitations regarding the absence of antimicrobial factors and degradability along with the low yield of production and extensive cultivation times (in large-scale production) still need to be resolved using suitable hybridization/modification strategies and optimization of conditions. The biocompatibility and bioactivity of BC-based materials along with their thermal, mechanical, and chemical stability are crucial aspects in designing TE scaffolds. Herein, cardiovascular TE applications of BC-based materials are deliberated, with a focus on the most recent advancements, important challenges, and future perspectives. Other biomaterials with cardiovascular TE applications and important roles of green nanotechnology in this field of science are covered to better compare and comprehensively review the subject. The application of BC-based materials and the collective roles of such biomaterials in the assembly of sustainable and natural-based scaffolds for cardiovascular TE are discussed.

In vitro/in vivoidentification of zein degraded peptides using HPLC-MS/MS and their safety evaluation

The identification of degraded products of implanted scaffolds is desirable to avoid regulatory concerns.In vivoidentification of products produced by the degradation of natural protein-based scaffolds is complex and demands the establishment of a routine analytical method. In this study, we developed a method for the identification of peptides produced by the degradation of zein bothin vitroandin vivousing high performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). Forin vitroexperiments, zein was degraded enzymatically and analyzed produced peptides.In vitrostudy showed cytocompatibility of peptides present in the hydrolysate of zein with no induction of apoptosis and cell senescence. Forin vivoexperiment, zein gels were prepared and subcutaneously implanted in rats. Peptides produced by the degradation of zein were identified and few were selected as targeted (unique peptides) and two peptides were synthesized as the reference sequence of these peptides. Further, peptide analysis using HPLC-MS/MS of different organs was performed after 2 and 8 weeks of implantation of zein gel in rats. It was found that zein-originated peptides were accumulated in different organs. QQHIIGGALF or peptides with same fractions were identified as unique peptides. These peptides were also found in control rats with regular rat feed, which means the degradation of implanted zein biomaterial produced food related peptides of non-toxic nature. Furthermore, hemotoxylin and eosin (H&E) staining exhibited normal features. Overall, zein degraded products showed cytocompatibility and did not induce organ toxicity, and QQHIIGGALF can act as a standard peptide for tracing and determining zein degradation. The study also provides the feasibility of complex analysis on identification and quantification of degradation products of protein-based scaffolds.

Self-assembled zein organogels as in situ forming implant drug delivery system and 3D printing ink

Recently, biomedical applications of organogels have been increasing; however, there is a demand for bio-based polymers. Here, we report self-assembled zein organogels in N-methyl pyrrolidone (NMP), Dimethyl sulfoxide (DMSO), and glycerol formal (GF). The gel formation was driven by the solvent's polarity and the hydrogen bonding component of Hansen Solubility Parameters was important in promoting gelation. Gels exhibited shear-thinning and thixotropic properties. Furthermore, water-induced self-assembly of zein allows mechanically robust in situ implant formation by solvent exchange. Ciprofloxacin was incorporated as a model drug and sustained release depending upon the solvent exchange rate was observed. In situ implants in agarose gel retained antibacterial efficacy against S. aureus for more than 14 days. Zein-based organogels were further applied as 3D printing ink and it was found that zein gel in DMSO had superior printability than gels prepared in NMP and GF. Using three solvents to prepare organogels can enable the encapsulation of various drugs and facilitate the preparation of composite gels with other biocompatible polymers. These organogel systems can further be used for developing 3D printed drug delivery systems or scaffolds for tissue engineering.

Zein-induced immune response and modulation by size, pore structure and drug-loading: Application for sciatic nerve regeneration

Zein is a biodegradable material with great potential in biomedical applications. However, as a plant-derived protein material, body's immune response is the key factor to determine its clinical performance. Herein, for the first time, the zein-induced immune response is evaluated systemically and locally, comparing with typical materials including alginate (ALG), poly(lactic-co-glycolic) acid (PLGA) and polystyrene (PS). Zein triggers an early inflammatory response consistent with the non-degradable PS, but this response decreases to the same level of the biosafe ALG and PLGA with zein degradation. Changing sphere sizes, pore structure and encapsulating dexamethasone can effectively modulate the zein-induced immune response, especially the pore structure which also inhibits neutrophil recruitment and promotes macrophages polarizing towards M2 phenotype. Thus, porous zein conduits with high and low porosity are further fabricated for the 15 mm sciatic nerve defect repair in rats. The conduits with high porosity induce more M2 macrophages to accelerate nerve regeneration with shorter degradation period and better nerve repair efficacy. These findings suggest that the pore structure in zein materials can alleviate the zein-induced early inflammation and promote M2 macrophage polarization to accelerate nerve regeneration. STATEMENT OF SIGNIFICANCE: Zein is a biodegradable material with great potential in biomedical applications. However, as a plant protein, its possible immune response in vivo is always the key issue. Until now, the systemic study on the immune responses of zein in vivo is still very limited, especially as an implant. Herein, for the first time, the zein-induced immune response was evaluated systemically and locally, comparing with typical biomaterials including alginate, poly(lactic-co-glycolic) acid and polystyrene. Changing sphere sizes, pore structure and encapsulating dexamethasone could effectively modulate the zein-induced immune response, especially the pore structure which also inhibited neutrophil recruitment and promoted macrophages polarizing towards M2 phenotype. Furthermore, the pore structure in zein nerve conduits was proved to alleviate the early inflammation and promote M2 macrophage polarization to accelerate nerve regeneration.

Regulatory Effect of Irresistin-16 on Competitive Dual-Species Biofilms Composed of Streptococcus mutans and Streptococcus sanguinis

Based on the ecological plaque hypothesis, suppressing opportunistic pathogens within biofilms, rather than killing microbes indiscriminately, could be a biofilm control strategy for managing dental caries. The present study aimed to evaluate the effects of irresistin-16 (IRS-16) on competitive dual-species biofilms, which consisted of the conditional cariogenic agent Streptococcus mutans (S. mutans) and oral commensal bacteria Streptococcus sanguinis (S. sanguinis). Bacterial growth and biofilm formation were monitored using growth curve and crystal violet staining, respectively. The microbial proportion was determined using fluorescence in situ hybridization. A 2, 5-diphenyltetrazolium bromide assay was used to measure the metabolic activity of biofilms. Bacterial/extracellular polysaccharide (EPS) dyeing, together with water-insoluble EPS measurements, were used to estimate EPS synthesis. A lactic acid assay was performed to detect lactic acid generation in biofilms. The cytotoxicity of IRS-16 was evaluated in mouse fibroblast L929 cells using a live/dead cell viability assay and cell counting kit-8 assay. Our results showed that IRS-16 exhibited selective anti-biofilm activity, leading to a remarkable survival disadvantage of S. mutans within competitive dual-species biofilms. In addition, the metabolic activity, EPS synthesis, and acid generation of dual-species biofilms were significantly reduced by IRS-16. Moreover, IRS-16 showed minimal cytotoxicity against mouse fibroblast L929 cells. In conclusion, IRS-16 exhibited remarkable regulatory effects on dual-species biofilms composed of S. mutans and S. sanguinis with low cytotoxicity, suggesting that it may have potential for use in caries management through ecological biofilm control.

Exploiting Redox-Complementary Peptide/Polyoxometalate Coacervates for Spontaneously Curing into Antimicrobial Adhesives

Recently, there has been a wave of reports on the fabrication of peptide-based underwater adhesives with the aim of understanding the adhesion mechanism of marine sessile organisms or creating new biomaterials beyond nature. However, the poor shear adhesion performance of the current peptide adhesives has largely hindered their applications. Herein, we proposed to sequentially perform the interfacial adhesion and bulk cohesion of peptide-based underwater adhesives using two redox-complementary peptide/polyoxometalate (POM) coacervates. The oxidative coacervates were prepared by mixing oxidative H₅PMo₁₀V₂O₄₀ and cationic peptides in an aqueous solution. The reductive coacervates consisted of K₅BW₁₂O₄₀ and cysteine-containing reductive peptides. Each of the individual coacervate has well-defined spreading capacity to achieve fast interfacial attachment and adhesion, but their cohesion is poor. However, after mixing the two redox-complementary coacervates at the target surface, effective adhesion and spontaneous curing were observed. We identified that the spontaneous curing resulted from the H₅PMo₁₀V₂O₄₀-regulated oxidization of cysteine-containing peptides. The formed intermolecular disulfide bonds improved the cross-linking density of the dual-peptide/POM coacervates, giving rise to the enhanced bulk cohesion and mechanical strength. More importantly, the resultant adhesives showcased excellent bioactivity to selectively suppress the growth of Gram-positive bacteria due to the presence of the polyoxometalates. This work raises further potential in the creation of biomimetic adhesives through the orchestrating of covalent and noncovalent interactions in a sequential fashion.

Zein based-nanoparticles loaded botanical pesticides in pest control: An enzyme stimuli-responsive approach aiming sustainable agriculture

Nanoencapsulation of biopesticides is an important strategy to increase the efficiency of these compounds, reducing losses and adverse effects on non-target organisms. This study describes the preparation and characterisation of zein nanoparticles containing the botanical compounds limonene and carvacrol, responsive to proteolytic enzymes present in the insects guts. The spherical nanoparticles, prepared by the anti-solvent precipitation method, presented in the nanoparticle tracking analysis (NTA) a concentration of 4.7 × 10¹² ± 1.3 × 10¹¹ particles.mL^-1 and an average size of 125 ± 2 nm. The formulations showed stability over time, in addition to not being phytotoxic to Phaseolus vulgaris plants. In vivo tests demonstrated that formulations of zein nanoparticles containing botanical compounds showed higher mortality to Spodoptera frugiperda larvae. In addition, the FTIC probe (fluorescein isothiocyanate) showed wide distribution in the larvae midgut, as well as being identified in the feces. The trypsin enzyme, as well as the enzymatic extract from insects midgut, was effective in the degradation of nanoparticles containing the mixture of botanical compounds, significantly reducing the concentration of nanoparticles and the changes in size distribution. The zein degradation was confirmed by the disappearance of the protein band in the electrophoresis gel, by the formation of the lower molecular weight fragments and also by the greater release of FTIC after enzymes incubation. In this context, the synthesis of responsive nanoparticles has great potential for application in pest management, increasing the selectivity and specificity of the system and contributing to a more sustainable agriculture.