Ethylene vinyl acetate as matrix for oral sustained release dosage forms produced via hot-melt extrusion

An alternative filament fabrication method as the basis for 3D-printing personalized implants from elastic ethylene vinyl acetate copolymer

In this work, a novel tool for small-scale filament production is presented. Unlike traditional methods such as hot melt extrusion (HME), the device (i) allows filament manufacturing from small material amounts as low as three grams, (ii) ensures high diameter stability almost independent of the viscoelastic behavior of the polymer melt, and (iii) enables processing of materials with rheological profiles specifically tailored toward fused filament fabrication (FFF). Hence, novel materials, previously difficult to process due to HME limitations, become easily accessible for FFF for the first time. Here, we showcase the production of highly flexible drug-free, and drug-loaded filaments based on ethylene-vinyl acetate polymers with a vinyl acetate content of 28 w% (EVA28) and unprecedented high melt flow rates of up to 400 g/10 min. Owing to their low viscosity, FFF with low print nozzle sizes of 250 μm was achieved for the first time for EVA28. These small nozzle diameters facilitate 3D-printing of high-resolution structures in small-dimensional dosage forms such as subcutaneous implantable drug delivery systems, which can later be used for personalization. Consequently, the material portfolio for FFF is tremendously broadened, allowing material and formulation optimization toward FFF, independent of a preliminary extrusion process.

Quality by design approach for fabrication of extended-release buccal films for xerostomia employing hot-melt extrusion technology

The study endeavors the fabrication of extended-release adipic acid (APA) buccal films employing a quality by design (QbD) approach. The films intended for the treatment of xerostomia were developed utilizing hot-melt extrusion technology. The patient-centered quality target product profile was created, and the critical quality attributes were identified accordingly. Three early-stage formulation development trials, complemented by risk assessment aligned the formulation and process parameters with the product quality standards. Employing a D-optimal mixture design, the formulations were systematically optimized by evaluating three formulation variables: amount of the release-controlling polymer Eudragit® (E RSPO), bioadhesive agent Carbopol® (CBP 971P), and pore forming agent polyethylene glycol (PEG 1500) as independent variables, and % APA release in 1, 4 and 8 h as responses. Using design of experiment software (Design-Expert®), a total of 16 experimental runs were computed and extruded using a Thermofisher ScientificTM twin screw extruder. All films exhibited acceptable content uniformity and extended-release profiles with the potential for releasing APA for at least 8 h. Films containing 30% E RSPO, 10% CBP 971P, and 20% PEG 1500 released 88.6% APA in 8 h. Increasing the CBP concentration enhanced adhesiveness and swelling capacities while decreasing E RSPO concentration yielded films with higher mechanical strength. The release kinetics fitted well into Higuchi and Krosmeyer-Peppas models indicating a Fickian diffusion release mechanism.

3D Printing Direct Powder Extrusion in the Production of Drug Delivery Systems: State of the Art and Future Perspectives

The production of tailored, on-demand drug delivery systems has gained attention in pharmaceutical development over the last few years, thanks to the application of 3D printing technology in the pharmaceutical field. Recently, direct powder extrusion (DPE) has emerged among the extrusion-based additive manufacturing techniques. It is a one-step procedure that allows the direct processing of powdered formulations. The aim of this systematic literature review is to analyze the production of drug delivery systems using DPE. A total of 27 articles have been identified through scientific databases (Scopus, PubMed, and ScienceDirect). The main characteristics of the three types of 3D printers based on DPE have been discussed. The selection of polymers and auxiliary excipients, as well as the flowability of the powder mixture, the rheological properties of the molten material, and the printing temperatures have been identified as the main critical parameters for successful printing. A wide range of drug delivery systems with varied geometries and different drug release profiles intended for oral, buccal, parenteral, and transdermal routes have been produced. The ability of this technique to manufacture personalized, on-demand drug delivery systems has been proven. For all these reasons, its implementation in hospital settings in the near future seems promising.

Polymer Delivery Systems for Long-Acting Antiretroviral Drugs

The success of long-acting (LA) drug delivery systems (DDSs) is linked to their biocompatible polymers. These are used for extended therapeutic release. For treatment or prevention of human immune deficiency virus type one (HIV-1) infection, LA DDSs hold promise for improved regimen adherence and reduced toxicities. Current examples include Cabenuva, Apretude, and Sunlenca. Each is safe and effective. Alternative promising DDSs include implants, prodrugs, vaginal rings, and microarray patches. Each can further meet patients' needs. We posit that the physicochemical properties of the formulation chemical design can optimize drug release profiles. We posit that the strategic design of LA DDS polymers will further improve controlled drug release to simplify dosing schedules and improve regimen adherence.

Amorphous solid dispersions: Stability mechanism, design strategy and key production technique of hot melt extrusion

Solid dispersion (SD) system has been used as an effective formulation strategy to increase in vitro and in vivo performances of poorly water-soluble drugs, such as solubility/dissolution, stability and bioavailability. This review provides a comprehensive SD classification and identifies the most popular amorphous solid dispersions (ASDs). Meanwhile, this review further puts forward the systematic design strategy of satisfactory ASDs in terms of drug properties, carrier selection, preparation methods and stabilization mechanisms. In addition, hot melt extrusion (HME) as the continuous manufacturing technique is described including the principle and structure of HME instrument, key process parameters and production application, in order to guide the scale-up of ASDs and develop more ASD products to the market in pharmaceutical industry.

Development and Evaluation of a Low-Cost Triglyceride Quantification Enzymatic Biosensor Using an Arduino-Based Microfluidic System

Overweight and obesity promote diabetes and heart disease onset. Triglycerides are key biomarkers for cardiovascular disease, strokes, and other health issues. Scientists have devised methods and instruments for the detection of these molecules in liquid samples. In this study, an enzymatic biosensor was developed using an Arduino-based microfluidic platform, wherein a lipolytic enzyme was immobilized on an ethylene-vinyl acetate polymer through physical adsorption. This low-cost optical biosensor employed a spectrophotometric transducer and was assessed in liquid samples to indirectly detect triglycerides and fatty acids using p-nitrophenol as an indicator. The average triglyceride level detected in the conducted experiments was 47.727 mg/dL. The biosensor exhibited a percentage of recovery of 81.12% and a variation coefficient of 0.791%. Furthermore, the biosensor demonstrated the ability to detect triglyceride levels without the need for sample dilution, ranging from 7.6741 mg/dL to 58.835 mg/dL. This study successfully developed an efficient and affordable enzymatic biosensor prototype for triglyceride and fatty acid detection. The lipolytic enzyme immobilization on the polymer substrate provided a stable and reproducible detection system, rendering this biosensor an exciting option for the detection of these molecules.

Characterization of Pharmaceutical Tablets by X-ray Tomography

Solid dosage forms such as tablets are extensively used in drug administration for their simplicity and large-scale manufacturing capabilities. High-resolution X-ray tomography is one of the most valuable non-destructive techniques to investigate the internal structure of the tablets for drug product development as well as for a cost effective production process. In this work, we review the recent developments in high-resolution X-ray microtomography and its application towards different tablet characterizations. The increased availability of powerful laboratory instrumentation, as well as the advent of high brilliance and coherent 3rd generation synchrotron light sources, combined with advanced data processing techniques, are driving the application of X-ray microtomography forward as an indispensable tool in the pharmaceutical industry.

3D-printed EVA-based patches manufactured by direct powder extrusion for personalized transdermal therapies

In recent years, 3D printing has attracted great interest in the pharmaceutical field as a promising tool for the on-demand manufacturing of patient-centered pharmaceutical forms. Among the existing 3D printing techniques, direct powder extrusion (DPE) resulted as the most practical approach thanks to the possibility to directly process excipients and drugs in a single step. The main goal of this work was to determine whether different grades of ethylene vinyl acetate (EVA) copolymer might be employed as new feedstock materials for the DPE technique to manufacture transdermal patches. By selecting two model drugs with different thermal behavior, (i.e., ibuprofen and diclofenac sodium) we also wanted to pay attention to the versatility of EVA excipient in preparing patches for customized transdermal therapies. EVA was combined with 30 % (w/w) of each model drugs. The physicochemical composition of the printed devices was investigated through Fourier-transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analyses. FT-IR spectra confirmed that the starting materials were effectively incorporated into the final formulation, and thermal analyses demonstrated that the extrusion process altered the crystalline morphology of the raw polymers inducing the formation of crystals at lower thicknesses. Lastly, the drug release and permeation profile of the printed systems was evaluated for 48 h and showed to be dependent on the VA content of the EVA grade (74.5 % of ibuprofen released from EVA 4030AC matrix and 12.6 % of diclofenac sodium released from EVA1821A matrix). Hence, this study demonstrated that EVA and direct powder extrusion technique could be promising tools for manufacturing transdermal patches. By selecting the EVA grade with the appropriate VA content, drugs with dissimilar melting points could be printed preserving their thermal stability. Moreover, the desired drug release and permeation profile of the drug can be achieved, representing an important advantage in terms of personalized medicine.

Removal of oils and organic solvents from wastewater through swelling of porous crosslinked poly(ethylene-co-vinyl acetate): Preparation of adsorbent and their oil removal efficiency

In this novel study, an attempt has been made to prepare porous crosslinked poly(ethylene-co-vinyl acetate) polymer (C-EVA). The porous C-EVA was prepared by grafting of maleic anhydride and cetyl alcohol onto the polymer backbone with addition of NaCl as porogen in the brabender mixture at 120 °C and 80 rpm. This was followed by leaching of NaCl with water extraction to generate a highly porous polymer structure which was evident from its SEM micrographs. The polymer was found to have excellent swelling capacity in various oils and organic solvents and showed good selective absorption capacity. The reusability of the synthesized polymer was studied and it was found that it could be reused for more than 30 absorption desorption cycles without undergoing much change in its absorption capacity. The cross-linked polymeric composite was further characterized by FTIR, TGA, XRD, and SEM.

The Quest for Child-Friendly Carrier Materials Used in the 3D Semi-Solid Extrusion Printing of Medicines

This work gives a brief overview of carrier materials currently used in pharmaceutical studies on the three-dimensional (3D) semi-solid extrusion (SSE) printing of medicines for pediatrics. The suitability of using these carrier materials in pediatric formulations, concerning safety and toxicity, was reviewed by consulting the 'Safety & Toxicity of Excipients for Pediatrics' (STEP) database and the Food and Drug Administration (FDA) regulations. In the second part of this work, carrier materials were tested on their ability to form a semi-solid mixture with lactose by dual asymmetric centrifugation (DAC) and printing by SSE. With the combination of theoretical and experimental studies, this work will guide research toward grounded decision-making when it comes to carrier material selection for pharmaceutical pediatric 3D SSE printing formulations.

Polymeric Biomaterials for Topical Drug Delivery in the Oral Cavity: Advances on Devices and Manufacturing Technologies

There are several routes of drug administration, and each one has advantages and limitations. In the case of the topical application in the oral cavity, comprising the buccal, sublingual, palatal, and gingival regions, the advantage is that it is painless, non-invasive, allows easy application of the formulation, and it is capable of avoiding the need of drug swallowing by the patient, a matter of relevance for children and the elderly. Another advantage is the high permeability of the oral mucosa, which may deliver very high amounts of medication rapidly to the bloodstream without significant damage to the stomach. This route also allows the local treatment of lesions that affect the oral cavity, as an alternative to systemic approaches involving injection-based methods and oral medications that require drug swallowing. Thus, this drug delivery route has been arousing great interest in the pharmaceutical industry. This review aims to condense information on the types of biomaterials and polymers used for this functionality, as well as on production methods and market perspectives of this topical drug delivery route.

Poly(2-alkyl-2-oxazoline)s: A polymer platform to sustain the release from tablets with a high drug loading

Sustaining the release of highly dosed APIs from a matrix tablet is challenging. To address this challenge, this study evaluated the performance of thermoplastic poly (2-alkyl-2-oxazoline)s (PAOx) as matrix excipient to produce sustained-release tablets via three processing routes: (a) hot-melt extrusion (HME) combined with injection molding (IM), (b) HME combined with milling and compression and (c) direct compression (DC). Different PAOx (co-)polymers and polymer mixtures were processed with several active pharmaceutical ingredients having different aqueous solubilities and melting temperatures (metoprolol tartrate (MPT), metformin hydrochloride (MTF) and theophylline anhydrous (THA)). Different PAOx grades were synthesized and purified by the Supramolecular Chemistry Group, and the effect of PAOx grade and processing technique on the in vitro release kinetics was evaluated. Using the hydrophobic poly (2-n-propyl-2-oxazoline) (PⁿPrOx) as a matrix excipient allowed to sustain the release of different APIs, even at a 70% (w/w) drug load. Whereas complete THA release was not achieved from the PⁿPrOx matrix over 24 ​h regardless of the processing technique, adding 7.5% w/w of the hydrophilic poly (2-ethyl-2-oxazoline) to the hydrophobic PⁿPrOx matrix significantly increased THA release, highlighting the relevance of mixing different PAOx grades. In addition, it was demonstrated that the release of THA was similar from co-polymer and polymer mixtures with the same polymer ratios. On the other hand, as the release of MTF from a PⁿPrOx matrix was fast, the more hydrophobic poly (2-sec-butyl-2-oxazoline) (P^secBuOx) was used to retard MTF release. In addition, a mixture between the hydrophilic PEtOx and the hydrophobic P^secBuOx allowed accurate tuning of the release of MTF formulations. Finally, it was demonstrated that PAOx also showed a high ability to tune the in vivo release. IM tablets containing 70% MTF and 30% P^secBuOx showed a lower in vivo bioavailability compared to IM tablets containing a low PEtOx concentration (7.5%, w/w) in combination with P^secBuOx (22.5%, w/w). Importantly, the in vivo MTF blood level from the sustained release tablets correlated well with the in vitro release profiles. In general, this work demonstrates that PAOx polymers offer a versatile formulation platform to adjust the release rate of different APIs, enabling sustained release from tablets with up to 70% w/w drug loading.

Development of Flow-Through Cell Dissolution Method for In Situ Visualization of Dissolution Processes in Solid Dosage Forms Using X-ray μCT

Visualization of the dynamic behavior of pharmaceutical dosage forms during the dissolution process offers a better understanding of the drug release mechanism, enabling the design of customized dosage forms. In this study, an X-ray tomography-based approach is proposed to monitor and analyze the dynamics of the structure at the pore scale level during the dissolution process. A flow-through cell dissolution apparatus was developed, capable of mimicking the standard in vitro dissolution process, which can be easily positioned in an X-ray tomography setup. The method was utilized to study the dissolution of a Capa^® (polycaprolactone)-based sustained-release 3D printed tablet. The impact of the flow rate on the active pharmaceutical ingredient (API) release rate was studied and 16 mL/min was selected as a suitable flow rate. Furthermore, cesium chloride (CsCl) was used as a contrast agent to increase the contrast between the sample and the dissolution medium. Data obtained with this novel technique were in a good agreement with the released drug rate acquired by the standard in vitro dissolution test (the similarity factor (f2) = 77%). Finally, the proposed approach allowed visualizing the internal structure of the sample, as well as real-time tracking of solution ingress into the product.

3D-Printed EVA Devices for Antiviral Delivery and Herpes Virus Control in Genital Infection

Herpes viruses are widespread in the human population and can cause many different diseases. Genital herpes is common and can increase the risk of HIV infection and neonatal herpes. Acyclovir is the most used drug for herpes treatment; however, it presents some disadvantages due to its poor oral bioavailability. In this study, some ethylene vinyl acetate devices with different acyclovir amounts (0, 10, and 20 wt.%) were manufactured by fused filament fabrication in two different geometries, an intrauterine device, and an intravaginal ring. Thermal analyses suggested that the crystallinity of EVA decreased up to 8% for the sample loaded with 20 wt.% of acyclovir. DSC, SEM, and FTIR analyses confirmed that the drug was successfully incorporated into the EVA matrix. Moreover, the drug release tests suggested a burst release during the first 24 h followed by a slower release rate sustained up to 80 days. Biological assays showed the biocompatibility of the EVA/ACV device, as well as a 99% reduction in vitro replication of HSV-1. Finally, the EVA presented a suitable performance for 3D printing manufacturing that can contribute to developing personalized solutions for long-term herpes treatment.

Ethylene-Vinyl Acetate (EVA) Containing Waste Hemp-Derived Biochar Fibers: Mechanical, Electrical, Thermal and Tribological Behavior

To reduce the use of carbon components sourced from fossil fuels, hemp fibers were pyrolyzed and utilized as filler to prepare EVA-based composites for automotive applications. The mechanical, tribological, electrical (DC and AC) and thermal properties of EVA/fiber biochar (HFB) composites containing different amounts of fibers (ranging from 5 to 40 wt.%) have been thoroughly studied. The morphological analysis highlighted an uneven dispersion of the filler within the polymer matrix, with poor interfacial adhesion. The presence of biochar fibers did not affect the thermal behavior of EVA (no significant changes of Tm, Tc and Tg were observed), notwithstanding a slight increase in the crystallinity degree, especially for EVA/HFB 90/10 and 80/20. Conversely, biochar fibers enhanced the thermo-oxidative stability of the composites, which increased with increasing the biochar content. EVA/HFB composites showed higher stiffness and lower ductility than neat EVA. In addition, high concentrations of fiber biochar allowed achieving higher thermal conductivity and microwave electrical conductivity. In particular, EVA/HFB 60/40 showed a thermal conductivity higher than that of neat EVA (respectively, 0.40 vs. 0.33 W·m^-1 ·K^-1); the same composite exhibited an up to twenty-fold increased microwave conductivity. Finally, the combination of stiffness, enhanced thermal conductivity and intrinsic lubricating features of the filler resulted in excellent wear resistance and friction reduction in comparison with unfilled EVA.

Hot-Melt Extrusion of the Thermo-Sensitive Peptidomimetic Drug Enalapril Maleate

The aim of this research was the production of extrudates for the treatment of hypertension and heart failure and the investigation of the degradation of the peptidomimetic drug enalapril maleate (EM) during hot-melt extrusion (HME). A fast HPLC method was developed to quantify enalapril maleate and possible degradation products. Screening experiments revealed that the diketopiperazine derivative (Impurity D) was the main degradation product. Hot-melt extrusion of enalapril maleate with the polymer Soluplus^® enabled extrusion at 100 °C, whereas a formulation with the polymer Eudragit^® E PO could be extruded at only 70 °C. Extrusion at 70 °C prevented thermal degradation. A stabilizing molecular interaction between enalapril maleate and Eudragit^® E PO was identified via FT-IR spectroscopy. Dissolution studies were carried out to study the influence of the formulation on the dissolution behavior of enalapril maleate. These promising results can be transferred to other thermo-sensitive and peptidomimetic drugs to produce extrudates which can be used, for instance, as feedstock material for the production of patient-specific dosage forms via Fused Deposition Modeling (FDM) 3D printing.

PVC/EVA-based polymer inclusion membranes with improved stability and Cr(VI) extraction capacity: Water plasticization effect

Polymer inclusion membranes (PIMs) are far investigated for their ability to extract heavy metals and small organic compounds from aqueous media. Polyvinyl chloride (PVC) is one of the most widely used base polymers for the PIM elaboration. However, its use requires the incorporation of a relatively expensive liquid plasticizer. In the present work, poly(ethylene-co-vinyl acetate) (EVA) serves as a polymer plasticizer for the elaboration of PIMs based on PVC as a base polymer and Aliquat 336 as a carrier. The composition of PIMs was optimized in terms of the PVC/EVA ratio and the vinyl acetate (VA) groups content (x) of EVA (i.e. EVA_x). Physical-chemical properties of the resulting membranes are analyzed and correlated with their structure. The results of SEM analysis revealed miscible PVC/EVA₇₀ blends (i.e. with 70 wt% of VA groups) and partially miscible PVC/EVA₄₀ blends. The plasticizing effect of the EVA copolymer was confirmed by the tensile test results. The results of transport measurements showed that PIMs containing EVA₄₀ and PVC are more efficient for the Cr(VI) extraction than those with only PVC. Thus, EVA₄₀ can effectively replace the conventional liquid plasticizers while improving the Cr(VI) permeability. Besides, it is stated that EVA₄₀-based PIMs are more stable as compared with conventional PIMs due to the water plasticizing effect. After the membrane optimization, the highest Cr(VI) transport flux (54.7 µmol·m^-2·s^-1) was measured. Moreover, the addition of 10 wt% of tetradecanol causes the increase of the water plasticizing effect and allows obtaining a PIM with high stability (up to 24 cycles) required for the membrane long-term operation.

Phase-Field Model for Drug Release of Water-Swellable Filaments for Fused Filament Fabrication

This paper treats the drug release process as a phase-field problem and a phase-field model capable of simulating the dynamics of multiple moving fronts, transient drug fluxes, and fractional drug release from swellable polymeric systems is proposed and validated experimentally. The model can not only capture accurately the positions and movements of the distinct fronts without tracking the locations of fronts explicitly but also predict well the release profile to the completion of the release process. The parametric study has shown that parameters including water diffusion coefficient, drug saturation solubility, drug diffusion coefficient, initial drug loading ratio, and initial porosity are critical in regulating the drug release kinetics. It has been also demonstrated that the model can be applied to the study of swellable filaments and has wide applicability for different materials. Due to explicit boundary position tracking being eliminated, the model paves the way for practical use and can be extended for dealing with geometrically complex drug delivery systems. It is a useful tool to guide the design of new controlled delivery systems fabricated by fused filament fabrication.

Curcumin Plant for Colorectal Cancer Prediction and Prevention Using In Silico Molecular Analysis; HOT-MELT Extrusion

The impact of a soluble complex (SC) of curcumin (CuR) synthesized using hot melt (HM) and hot-melt extrusion (HE) technologies on adenocarcinoma cells for the treatment of colorectal cancer by enhancing CuR solubility is investigated in this work. In silico molecular modelling, solubility, drug release, and physicochemical analysis were all part of the phase solubility (PS) study, which featured a novel dyeing test and a central composite design to optimize the best complex (CDD). The optimal HE-SC (1 : 5) enhances solubility (0.8521 ± 0.016 mg·mL-1) and dissolution (91.87 ± 0.208% at 30 min), and it has an ideal stability constant (309 and 377 M-1) at 25 and 37°C and an AL type of isotherm, implying 1 : 1 stoichiometry according to the findings. An intermolecular hydrogen bond that has not undergone any chemical change and has resulted in the complete conversion of the amorphous form aids in the creation of SC. In vitro cytotoxicity was measured at IC50 on the SW480 (72 M·mL-1) and Caco-2 (40 M·mL-1) cells. According to apoptotic studies, apoptosis was responsible for the vast majority of cell death, with necrosis accounting for a small proportion of the total. In vivo toxicity was established using a zebrafish model, and a western blot examination revealed apoptosis at the molecular level. It was argued that the novel formulations developed using HE technology are more significant and effective than existing pure CuR formulations.

An Ideal Approach for Enhancing 5-Fluorouracil Anticancer Efficacy by Nanoemulsion for Cytotoxicity against a Human Hepatoma Cell Line (HepG2 Cells)

The core objectives of the research were to prepare 5-fluorouracil nanoemulsion (FU-NE) and to evaluate the physiochemical properties and to study the in vitro antiproliferation in HepG2 cell lines. The physiochemical parameters determined were compatibility, particle size (PS), polydispersity index (PDI), zeta potential (ZP), density, surface tension (ST), pH, viscosity, in vitro release of FU, cytotoxicity, and apoptosis study. The prepared FU-NE3 was stable, sterile, and homogeneous. On the HepG2 (120 μg.mL-1) cells, in vitro cytotoxicity was obtained at IC50 concentration. Apoptosis examination by AO/EBand Hoechst staining shows that the majority of cell demise was caused by apoptosis, with a tiny fraction of necrosis. Hence, this investigation concluded that the developed FU-NE has now desirable characteristics for drug delivery to the cancer cell and may be screened for the in vivo colorectal anticancer activity.

Extrusion and 3D printing of novel lipid-polymer blends for oral drug applications

Lipids are interesting biological materials that can offer a number of pharmaceutical benefits when used as carriers for drug delivery. However, 3D printing of lipids alone by fused deposition processing techniques is very difficult as they have very poor mechanical properties that cause their filaments to fail when they are loaded into a fused deposition 3D printer. If this problem could be overcome, then lipids could be 3D printed into bespoke tablets and assist progress towards such personalised medicines. This work aims to improve the mechanical properties of lipid filaments by developing novel lipid-EVA (ethylene vinyl acetate) blends suitable for 3D printing. Different types of lipids in varying proportions were melt blended with EVA and extruded using a micro compounder. The ultimate printability of the materials was tested by feeding the filaments into a material extrusion 3D printer. Flexural testing of the extruded blends demonstrates that a good balance between the strength and flexibility is required for a material to be printable and it was found that a filament has to have a modulus/strength ratio between 8 and 25 in order to be printable. SEM analysis of the fracture surface shows a network structure within the lipid matrix that could be playing a role in the improved properties of the best performing blends. DSC thermograms show a shift in thermal transitions, suggesting some level of miscibility of the components that could have contributed to a more robust structure. The TGA results show an onset of degradation of the blends greater than 200 °C, indicating that the materials can readily withstand the extrusion and printing temperatures. This study demonstrates the successful extrusion and 3D printing of novel EVA-lipid blends with lipid contents of up to 90%.

Medical Applications of Porous Biomaterials: Features of Porosity and Tissue-Specific Implications for Biocompatibility

Porosity is an important material feature commonly employed in implants and tissue scaffolds. The presence of material voids permits the infiltration of cells, mechanical compliance, and outward diffusion of pharmaceutical agents. Various studies have confirmed that porosity indeed promotes favorable tissue responses, including minimal fibrous encapsulation during the foreign body reaction (FBR). However, increased biofilm formation and calcification is also described to arise due to biomaterial porosity. Additionally, the relevance of host responses like the FBR, infection, calcification, and thrombosis are dependent on tissue location and specific tissue microenvironment. In this review, the features of porous materials and the implications of porosity in the context of medical devices is discussed. Common methods to create porous materials are also discussed, as well as the parameters that are used to tune pore features. Responses toward porous biomaterials are also reviewed, including the various stages of the FBR, hemocompatibility, biofilm formation, and calcification. Finally, these host responses are considered in tissue specific locations including the subcutis, bone, cardiovascular system, brain, eye, and female reproductive tract. The effects of porosity across the various tissues of the body is highlighted and the need to consider the tissue context when engineering biomaterials is emphasized.

Development of 3D printed drug-eluting contact lenses

OBJECTIVES

The aim of the work was to introduce 3D printing technology for the design and fabrication of drug-eluting contact lenses (DECL) for the treatment of glaucoma. The development of 3D printed lenses can effectively overcome drawbacks of existing approaches by using biocompatible medical grade polymers that provide sustained drug release of timolol maleate for extended periods.

METHODS

Hot melt extrusion was coupled with fusion deposition modelling (FDM) to produce printable filaments of ethylene-vinyl acetate copolymer-polylactic acid blends at various ratios loaded with timolol maleate. Physicochemical and mechanical characterisation of the printed filaments was used to optimise the printing of the contact lenses.

KEY FINDINGS

3D printed lenses with an aperture (opening) and specified dimensions could be printed using FDM technology. The lenses presented a smooth surface with good printing resolution while providing sustained release of timolol maleate over 3 days. The findings of this study can be used for the development of personalised DECL in the future.

Control Release and Diffusion-Reaction Kinetics of Genipin-Eluting Fibers Using an in Vitro Aneurysm Flow Model

The minimally invasive treatment of intracranial aneurysms by endovascular coiling is attractive yet faces challenges related to the degradation of fibrin clots in the aneurysm sac over time. Fibrin gels cross-linked with genipin exhibit enhanced mechanical and chemical stability, but there are many unknowns related to best practices for delivery from endovascular devices and subsequent integration of cross-linkers with the nascent clot. Here, we describe the in vitro characterization of genipin-eluting polymer fibers prepared by coextrusion with poly(ethylene-co-vinyl acetate). Genipin incorporation and release from these fibers are characterized by various gravimetric and spectroscopic techniques. Genipin release adheres to Higuchi kinetics with Higuchi constants varying between (2.44 ± 0.83) × 10^-7 and (8.41 ± 0.82) × 10^-7 mol·h^-0.5 depending on genipin loading and vinyl acetate concentration in the polymer matrix. The diffusion-reaction kinetics of genipin released from polymeric fibers within fibrin hydrogels was investigated using an in vitro aneurysm flow model. Spatiotemporal maps of genipin cross-linking density in fibrin gels produced by absorbance measurements suggest that genipin cross-link concentrations up to 9,993.87 ± 909.01 μM can be achieved. This work describes relevant diffusion-reaction parameters of genipin in fibrin gels and establishes the viability of genipin-eluting fibers as a platform for improving endovascular embolization of intracranial aneurysms.

Preparation of Soluble Complex of Curcumin for the Potential Antagonistic Effects on Human Colorectal Adenocarcinoma Cells

This study was designed to investigate the effects of curcumin (CMN) soluble complex (SC) prepared by melt casting (HM) and hot-melt extrusion (HME) technology. Phase solubility (PS) study, in silico molecular modeling, aqueous solubility, drug release, and physicochemical investigation including a novel dyeing test was performed to obtain an optimized complex by a central composite design (CCD). The results show that the HME-SC produces better improvements towards solubility (0.852 ± 0.02), dissolution (91.87 ± 0.21% at 30 min), with an ideal stability constant (309 and 377 M⁻¹ at 25 and 37 °C, respectively) and exhibits A_L type of isotherm indicating 1:1 stoichiometry. Intermolecular hydrogen bonding involves the formation of SC, which does not undergo any chemical modification, followed by the complete conversion of the amorphous form which was identified by XRD. The in vitro cytotoxicity showed that IC₅₀ was achieved in the SW480 (72 µM.mL⁻¹) and Caco-2 (40 µM.mL⁻¹) cells while that of pure CMN ranged from 146 to 116 µM/mL⁻¹. Apoptosis studies showed that cell death is primarily due to apoptosis, with a low rate of necrosis. In vivo toxicity, confirmed by the zebrafish model, exhibited the safety of the HME-SC. In conclusion, the HME-SC potentially enhances the solubility and cytotoxicity to the treatment of colorectal cancer (CRC).

Heat Treatment Induced Specified Aggregation Morphology of Metoprolol Tartrate in Poly(ε-caprolactone) Matrix and the Drug Release Variation

Hot-melt blending has been widely used in the pharmaceutical industry to produce drug delivery systems, however, realizing the controlled drug release behavior of a hot-melt blended medicament it is still a tough challenge. In this study, we developed a simple and effective heat treatment method to adjust the drug release behavior, without the addition of any release modifiers. Thin metoprolol tartrate (MPT)/poly(ε-caprolactone) (PCL) tablets were prepared through hot-melt processing, and different morphologies of MPT were obtained by altering processing temperatures and the following heat treatment. MPT particles with different particle sizes were obtained under different processing temperatures, and fibrous crystals of MPT were fabricated during the following heat treatment. Different morphological structures of MPT adjusted the drug diffusion channel when immersed in phosphate-buffered saline (PBS), and various drug release behaviors were approached. After being immersed for 24 h, 7% of the MPT was released from the blend processed at 130 °C, while more than 95% of the MPT were released after the following heat treatment of the same sample. Thus, flexible drug release behaviors were achieved using this simple and effective processing manufacture, which is demonstrated to be of profound importance for biomedical applications.

Can filaments, pellets and powder be used as feedstock to produce highly drug-loaded ethylene-vinyl acetate 3D printed tablets using extrusion-based additive manufacturing?

Personalized medicine, produced through 3D printing, is a promising approach for delivering the required drug dose based on the patient's profile. The primary purpose of this study was to investigate the potential of two different extrusion-based additive manufacturing techniques - fused filament fabrication (FFF) and screw-based 3D printing, also known as direct extrusion additive manufacturing (DEAM). Different ethylene-vinyl acetate (EVA) copolymers (9 %VA, 12 %VA, 16 %VA, 18 %VA, 25 %VA, 28 %VA, and 40 %VA) were selected and loaded with 50% (w/w) metoprolol tartrate (MPT). Hot-melt extrusion was performed to produce the drug-loaded filaments. These filaments were used for FFF in which the mechanical and rheological properties were rate-limiting steps. The drug-loaded filament based on the 18 %VA polymer was the only printable formulation due to its appropriate mechanical and rheological properties. As for the highest VA content (40 %VA), the feeding pinch rolls cause buckling of the filaments due to insufficient stiffness, while other filaments were successfully feedable towards the extrusion nozzle. However, poor flowability out of the extrusion nozzle due to the rheological limitation excluded these formulations from the initial printing trials. Filaments were also pelletized and used for pellets-DEAM. This method showed freedom in formulation selection because the screw rotation drives the material flow with less dependence on their mechanical properties. All drug-loaded pellets were successfully printed via DEAM, as sufficient pressure was built up towards the nozzle due to single screw extrusion processing method. In contrast, filaments were used as a piston to build up the pressure required for extrusion in filament-based printing, which highly depends on the filament's mechanical properties. Moreover, printing trials using a physical mixture in powder form were also investigated and showed promising results. In vitro drug release showed similar release patterns for MPT-loaded 3D printed tablets regardless of the printing technique. Additionally, pellets-DEAM enabled the production of tablets with the highest VA content, which failed in FFF 3D printing but showed an interesting delayed release profile.

Hot-Melt Extrusion: a Roadmap for Product Development

Hot-melt extrusion has found extensive application as a feasible pharmaceutical technological option over recent years. HME applications include solubility enhancement, taste masking, and sustained drug release. As bioavailability enhancement is a hot topic of today's science, one of the main applications of HME is centered on amorphous solid dispersions. This review describes the most significant aspects of HME technology and its use to prepare solid dispersions as a drug formulation strategy to enhance the solubility of poorly soluble drugs. It also addresses molecular and thermodynamic features critical for the physicochemical properties of these systems, mainly in what concerns miscibility and physical stability. Moreover, the importance of applying the Quality by Design philosophy in drug development is also discussed, as well as process analytical technologies in pharmaceutical HME monitoring, under the current standards of product development and regulatory guidance. Graphical Abstract.

The Vaginal Microbiota, Bacterial Biofilms and Polymeric Drug-Releasing Vaginal Rings

The diversity and dynamics of the microbial species populating the human vagina are increasingly understood to play a pivotal role in vaginal health. However, our knowledge about the potential interactions between the vaginal microbiota and vaginally administered drug delivery systems is still rather limited. Several drug-releasing vaginal ring products are currently marketed for hormonal contraception and estrogen replacement therapy, and many others are in preclinical and clinical development for these and other clinical indications. As with all implantable polymeric devices, drug-releasing vaginal rings are subject to surface bacterial adherence and biofilm formation, mostly associated with endogenous microorganisms present in the vagina. Despite more than 50 years since the vaginal ring concept was first described, there has been only limited study and reporting around bacterial adherence and biofilm formation on rings. With increasing interest in the vaginal microbiome and vaginal ring technology, this timely review article provides an overview of: (i) the vaginal microbiota, (ii) biofilm formation in the human vagina and its potential role in vaginal dysbiosis, (iii) mechanistic aspects of biofilm formation on polymeric surfaces, (iv) polymeric materials used in the manufacture of vaginal rings, (v) surface morphology characteristics of rings, (vi) biomass accumulation and biofilm formation on vaginal rings, and (vii) regulatory considerations.

Polymeric Implants for the Treatment of Intraocular Eye Diseases: Trends in Biodegradable and Non-Biodegradable Materials

Intraocular/Intravitreal implants constitute a relatively new method to treat eye diseases successfully due to the possibility of releasing drugs in a controlled and prolonged way. This particularity has made this kind of method preferred over other methods such as intravitreal injections or eye drops. However, there are some risks and complications associated with the use of eye implants, the body response being the most important. Therefore, material selection is a crucial factor to be considered for patient care since implant acceptance is closely related to the physical and chemical properties of the material from which the device is made. In this regard, there are two major categories of materials used in the development of eye implants: non-biodegradables and biodegradables. Although non-biodegradable implants are able to work as drug reservoirs, their surgical requirements make them uncomfortable and invasive for the patient and may put the eyeball at risk. Therefore, it would be expected that the human body responds better when treated with biodegradable implants due to their inherent nature and fewer surgical concerns. Thus, this review provides a summary and discussion of the most common non-biodegradable and biodegradable materials employed for the development of experimental and commercially available ocular delivery implants.

Hot melt extrusion: An emerging manufacturing method for slow and sustained protein delivery

With the rapid development of the biopharmaceutical industry, an increasing number of new therapeutic protein products (TPPs) have been approved by the FDA and many others are under pre-clinical and clinical evaluation. A major limitation of biopharmaceuticals is their limited half-life when administered systemically. A one-time, implantable, sustained protein delivery device would be advantageous in order to improve the quality of life of patients. Hot melt extrusion (HME) is a mature technology that has been extensively used for a broad spectrum of applications in the polymer and pharmaceutical industry and has achieved success as evidenced by a variety of FDA-approved commercial products. These commercial products are mostly for sustained delivery of small molecule therapeutics, leaving a significant gap for HME formulation of therapeutic proteins. With the increasing need of sustained TPP delivery, HME shows promise as a downstream processing method due to its high efficiency and economic value. Several challenges remain for the application of HME in protein delivery. Progress of HME for protein delivery, challenges encountered, and potential solutions will be detailed in this review article. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Development of Porous Polyurethane Implants Manufactured via Hot-Melt Extrusion

Implantable drug delivery systems (IDDSs) offer good patient compliance and allow the controlled delivery of drugs over prolonged times. However, their application is limited due to the scarce material selection and the limited technological possibilities to achieve extended drug release. Porous structures are an alternative strategy that can overcome these shortcomings. The present work focuses on the development of porous IDDS based on hydrophilic (HPL) and hydrophobic (HPB) polyurethanes and chemical pore formers (PFs) manufactured by hot-melt extrusion. Different PF types and concentrations were investigated to gain a sound understanding in terms of extrudate density, porosity, compressive behavior, pore morphology and liquid uptake. Based on the rheological analyses, a stable extrusion process guaranteed porosities of up to 40% using NaHCO3 as PF. The average pore diameter was between 140 and 600 µm and was indirectly proportional to the concentration of PF. The liquid uptake of HPB was determined by the open pores, while for HPL both open and closed pores influenced the uptake. In summary, through the rational selection of the polymer type, the PF type and concentration, porous carrier systems can be produced continuously via extrusion, whose properties can be adapted to the respective application site.

Bioavailability Enhancement of Olmesartan Medoxomil Using Hot-Melt Extrusion: In-Silico, In-Vitro, and In-Vivo Evaluation

Olmesartan medoxomil (OLM) an antihypertensive molecule with poor solubility and poor bioavailability (26% when taken orally) was selected as a model drug. Herein, rationale development of amorphous solid dispersion with hot-melt extrusion of poorly bioavailable OLM was carried out with the aid of quality by design (QbD), in-silico, in-vitro, and in-vivo evaluations. Polymer selection commenced with the selection of thermoplastic water-soluble polymers with the compatible processing temperature window as per the thermal behavior of OLM. Molecular dynamics (MD) simulations as well assisted in the selection of a carrier. Promising dissolution enhancement was observed with the help of Kollidon VA-64 (VA-64) as a carrier. Optimization of the formulation was executed using the QbD approach with design of experiment as a statistical optimization tool. Interactions between VA-64 and OLM on the atomic level were studied with the help of atomistic MD simulations. Characterization of the optimized extrudates were carried out with scanning electron microscopy, atomic force microscopy, differential scanning calorimetry, thermogravimetric analysis, Fourier transforms infrared spectroscopy, powder X-ray diffraction, in-vitro dissolution study, and in-vivo pharmacokinetic studies. Molecular-level mixing of OLM with VA-64 resulted into glass solution formation which rapidly dissolves (28 times in-vitro dissolution enhancement) in GI tract fluids and instantly gets absorbed into blood circulation. In-vivo pharmacokinetic studies performed in Sprague-Dawley rats reflected superior bioavailability (201.60%) with a significant increase in the C_max with short T_max through amorphization of OLM. The in-silico results were in agreement with the observed results of in-vitro dissolution studies and in-vivo pharmacokinetic study.

Controlled-Release from High-Loaded Reservoir-Type Systems-A Case Study of Ethylene-Vinyl Acetate and Progesterone

Reservoir systems (drug-loaded core surrounded by drug-free membrane) provide long-term controlled drug release. This is especially beneficial for drug delivery to specific body regions including the vagina. In this study, we investigated the potential of reservoir systems to provide high drug release rates over several weeks. The considered model system was an intra-vaginal ring (IVR) delivering progesterone (P4) in the mg/day range using ethylene-vinyl acetate (EVA) as release rate-controlling polymers. To circumvent the high material needs associated with IVR manufacturing, we implemented a small-scale screening procedure that predicts the drug release from IVRs. Formulations were designed based on the solubility and diffusivity of P4 in EVAs with varying vinyl acetate content. High in-vitro P4 release was achieved by i) high P4 solubility in the core polymer; ii) high P4 partition coefficient between the membrane and the core; and/or iii) low membrane thicknesses. It was challenging for systems designed to release comparatively high fractions of P4 at early times to retain a constant drug release over a long time. P4 crystal dissolution in the core could not counterbalance drug diffusion through the membrane and drug crystal dissolution was found to be the rate-limiting step. Overall, high P4 release rates can be achieved from EVA-based reservoir systems.

Fabrication, Characterization, and Properties of Poly (Ethylene-Co-Vinyl Acetate) Composite Thin Films Doped with Piezoelectric Nanofillers

Ethylene vinyl acetate (EVA) is a copolymer comprehending the semi-crystalline polyethylene and amorphous vinyl acetate phases, which potentially allow the fabrication of tunable materials. This paper aims at describing the fabrication and characterization of nanocomposite thin films made of polyethylene vinyl acetate, at different polymer concentration and vinyl acetate content, doped with piezoelectric nanomaterials, namely zinc oxide and barium titanate. These membranes are prepared by solvent casting, achieving a thickness in the order of 100-200 µm. The nanocomposites are characterized in terms of morphological, mechanical, and chemical properties. Analysis of the nanocomposites shows the nanofillers to be homogeneously dispersed in EVA matrix at different vinyl acetate content. Their influence is also noted in the mechanical behavior of thin films, which elastic modulus ranged from about 2 to 25 MPa, while keeping an elongation break from 600% to 1500% and tensile strength from 2 up to 13 MPa. At the same time, doped nanocomposite materials increase their crystallinity degree than the bare ones. The radiopacity provided by the addition of the dopant agents is proven. Finally, the direct piezoelectricity of nanocomposites membranes is demonstrated, showing higher voltage outputs (up to 2.5 V) for stiffer doped matrices. These results show the potentialities provided by the addition of piezoelectric nanomaterials towards mechanical reinforcement of EVA-based matrices while introducing radiopaque properties and responsiveness to mechanical stimuli.

Nanocomposite thin films based on polyethylene vinyl acetate and piezoelectric nanomaterials

This paper aims at describing the fabrication and characterization of nanocomposite thin films based on polyethylene vinyl acetate, at different content of vinyl acetate, and piezoelectric nanomaterials, namely zinc oxide and barium titanate. These membranes were prepared by casting, achieving a thickness in the order of 160-210 μm. The nanocomposites were characterized in terms of morphological, mechanical and chemical properties, finding a homogeneous distribution of nanomaterials, and the elastic modulus ranges from 2 to 25 MPa, while keeping an elongation break from 750 to 1500 % and tensile strength from 2.5 MPa up to 10 MPa. These results show the potential of these nanocomposite formulations as smart composite thin films for a series of biomedical applications, including the regeneration of osteoarticular tissues.

Hot-Melt Preparation of a Non-Biodegradable Peptide Implant: A Proof of Principle

BACKGROUND

Both biodegradable and non-biodegradable peptide-loaded implants are already developed for the long-term treatment of patients, thereby reducing the frequency of drug administration. To further improve peptide formulation, extending the scope of implant-based drug delivery systems towards other polymers and processing techniques is highly interesting.

OBJECTIVE

In this study, as a proof-of-principle, the feasibility of hot-melt processing of a peptide active pharmaceutical ingredient was assessed by developing a non-biodegradable poly(ethylenevinyl acetate) (33% VA) implant loaded with 20% (w/w) buserelin acetate.

METHODS

Cross-sectional implant characterization was performed by Raman microscopy. The stability of buserelin acetate in the polymeric matrix was evaluated for 3 months under ICH stability conditions and the quantity as well as the degradation products analyzed using LC-UV methods. An in vitro dissolution study was performed as well and buserelin acetate and its degradants analyzed using the same chromatographic methods.

RESULTS

No significant quantities of buserelin acetate-related degradation products were formed during the hot-melt preparation as well as during the stability study. Together with the consistent buserelin acetate assay values over time, chemical peptide stability was thus demonstrated. The in vitro buserelin acetate release from the implant was found to be diffusion-controlled after an initial burst release, with stable release profiles in the stability study, demonstrating the functional stability of the peptide implant.

CONCLUSION

These results indicate the feasibility of preparing non-biodegradable peptide-loaded implants using the hot-melt production method and may act as a proof of principle concept for further innovation in peptide medicinal formulations.

Twin-screw extrusion of sustained-release oral dosage forms and medical implants

Most of published reviews of twin-screw extrusion focused on its application for enhancing the bioavailability of amorphous solid dispersions while few of them focused on its use for manufacturing sustained-release oral dosage forms and medical implants, despite the considerable interest and success this process has garnered both in academia and in the pharmaceutical industry. Compared to conventional batch processing, twin-screw extrusion offers the advantages of continuous processing and the ability to prepare oral dosage forms and medical implants that have unique physicochemical and drug release attributes. This review provides an in-depth analysis of the formulation composition and processing conditions of twin-screw extrusion and how these factors affect the drug release properties of sustained-release dosage forms. This review also illustrates the unique advantages of this process by presenting case studies of a wide variety of commercial sustained-release products manufactured using twin-screw extrusion.

An Insight into Stabilization Mechanism of a Solid Dispersion of Indomethacin/Partially Hydrolyzed Polyvinyl Alcohol Prepared by Hot-Melt Extrusion

We examined the effect of hot-melt extrusion condition on the physical stability of the solid dispersion prepared using partially hydrolyzed polyvinyl alcohol (PVOH). The hot-melt extrusion of indomethacin (IMC) and PVOH mixed at the weight ratio of 3 : 7, 5 : 5 and 7 : 3 was performed either at 170 or 190°C to prepare the IMC/PVOH hot-melt extrudate (HME). Differential scanning calorimetry represented that IMC was mixed with PVOH on a scale of several tens of nanometer in all the HMEs with different weight ratio. ¹³C solid-state NMR measurement revealed that an intermolecular interaction was formed between a carboxylic group of IMC and a hydroxy group of PVOH in the HMEs. The intermolecular interaction in the HMEs was stronger at the higher extrusion temperature. At the low IMC loading, the IMC molecules could be mixed with the amorphous PVOH at the molecular level, and the remained PVOH without interaction formed the crystal phase. On the other hand, at the high IMC loading, most PVOH could be amorphized by the interaction with IMC, and the excess IMC which did not interact with PVOH formed the IMC-rich domain. The IMC/PVOH HME at the weight ratio of 7 : 3 extruded at higher extrusion temperature showed higher physical stability of amorphous IMC compared with that extruded at lower extrusion temperature. The hot-melt extrusion process at higher temperature provided the rapid melting of PVOH crystal phase, resulted in the homogeneous mixing with IMC and the formation of stronger intermolecular interaction.