Pressure-assisted Microsyringe Research Articles

Combining the potential of 3D printed buccal films and nanostructured lipid carriers for personalised cannabidiol delivery

Cannabidiol (CBD) has been recognized for its numerous therapeutic benefits, such as neuroprotection, anti-inflammatory effects, and cardioprotection. However, CBD has some limitations, including unpredictable pharmacokinetics and low oral bioavailability. To overcome the challenges associated with CBD delivery, we employed Design of Experiments (DoE), lipid carriers, and 3D printing techniques to optimize and develop buccal film loaded with CBD-NLCs. Three-factor Box-Behnken Design was carried out to optimise the NLCs and analyse the effect of independent factors on dependent factors. The emulsification-ultrasonication technique was used to prepare the NLCs. A pressure-assisted micro-syringe printing technique was used to produce the films. The produced films were studied for physicochemical, and mechanical properties, release profiles, and predicted in vivo performance. The observed particle size of the NLCs ranged from 12.17 to 84.91 nm whereas the PDI varied from 0.099 to 0.298. Lipid and sonication time positively affected the particle size whereas the surfactant concentration was inversely related. CBD was incorporated into the optimal formulation and the observed particle size, PDI, and zeta potential for the CBD-NLCs were 94.2 ± 0.47 nm, 0.11 ± 0.01 and − 11.8 ± 0.52 mV. Hydroxyethyl cellulose (HEC)-based gel containing the CBD-NLCs was prepared and used as a feed for 3D printing. The CBD-NLCs film demonstrated a slow and sustained in vitro release profile (84. 11 ± 7.02% in 6 h). The predicted AUC0–10 h, Cmax, and Tmax were 201.5 µg·h/L, 0.74 µg/L, and 1.28 h for a film with 0.4 mg of CBD, respectively. The finding demonstrates that a buccal film of CBD-NLCs can be fabricated using 3D printing.Graphical

The Optimization of Pressure-Assisted Microsyringe (PAM) 3D Printing Parameters for the Development of Sustainable Starch-Based Patches.

The aim of this work was to develop sustainable patches for wound application, using the biopolymer starch, created using a low-cost 3D printing PAM device. The composition of a starch gel was optimized for PAM extrusion: corn starch 10% w/w, β-glucan water suspension (filler, 1% w/w), glycerol (plasticizer, 29% w/w), and water 60% w/w. The most suitable 3D printing parameters were optimized as well (nozzle size 0.8 mm, layer height 0.2 mm, infill 100%, volumetric flow rate 3.02 mm3/s, and print speed 15 mm/s). The suitable conditions for post-printing drying were set at 37 °C for 24 h. The obtained patch was homogenous but with low mechanical resistance. To solve this problem, the starch gel was extruded over an alginate support, which, after drying, becomes an integral part of the product, constituting the backing layer of the final formulation. This approach significantly improved the physicochemical and post-printing properties of the final bilayer patch, showing suitable mechanical properties such as elastic modulus (3.80 ± 0.82 MPa), strength (0.92 ± 0.08 MPa), and deformation at break (50 ± 1%). The obtained results suggest the possibility of low-cost production of patches for wound treatment by additive manufacturing technology.

Development of an anti-infective urinary catheter composed of polyvinyl alcohol/sodium alginate/methylcellulose/polyethylene glycol by using a pressure-assisted 3D-printing technique

Catheter-associated urinary tract infections (CAUTI) are a common complication associated with catheterization, leading to urosepsis, bacteriuria, and septicaemia. The present work focuses on 3D printing a urinary catheter with anti-infective properties using various concentrations of polyvinyl alcohol (PVA, e.g., 6–8 %), sodium alginate (NaAlg, e.g. 1–4 %), methylcellulose (MC, 5 %), polyethylene glycol (PEG, 5 %) impregnated with secnidazole, an antibiotic acting against Gram-negative bacteria. To produce suitable polymer ink for Pressure Assisted Microsyringe (PAM) 3D printing, the cross-linked between NaAlg and calcium chloride is necessary to prepare the catheter. The optimised catheter was found to have an outer diameter of 5 mm, an inner diameter of 3.5 mm, and a length of the catheter of 50 mm. The analysis by various methods confirms the successful incorporation of secnidazole in the 3D-printed catheter. A drug-loaded/coated catheter showed an initial drug release of 79 % following a sustained release to reach 100 % within 5 h. Weibull model fits well with the drug release data. The release models suggest the Quasi-Fickian diffusion mechanism from the system. Moreover, the secnidazole 3D printed catheter disrupted biofilms and suppressed all the Quorum sensing mediated virulence factors of two important keystone pathogens causing urinary tract infections.

Additive Manufacturing of an Extended-Release Tablet of Tacrolimus.

An extended-release tablet of tacrolimus as once-daily dosing was fabricated using 3D printing technology. It was developed by combining two 3D-printing methods in parallel. Indeed, an optimized mixture of PVA, sorbitol, and magnesium stearate as a shell compartment was printed through a hot-melt extrusion (HME) nozzle while an HPMC gel mixture of the drug in the core compartment was printed by a pressure-assisted micro-syringe (PAM). A 3D-printed tablet with an infill of 90% was selected as an optimized formula upon the desired dissolution profile, releasing 86% of the drug at 12 h, similar to the commercial one. The weight variation, friability, hardness, assay, and content uniformity determination met USP requirements. A microbial evaluation showed that the 3D-printed tablet does not support microbial growth. SEM analysis showed smooth surfaces with multiple deposited layers. No peak interference appeared based on FTIR analysis. No decomposition of the polymer and drug was observed in the printing temperature, and no change in tacrolimus crystallinity was detected based on TGA and DSC analyses, respectively. The novel, sTable 3D-printed tablet, fabricated using controllable additive manufacturing, can quickly provide tailored dosing with specific kinetic release for personalized medicine at the point-of-care.

Formulation and characterization of pressure-assisted microsyringe 3D-printed scaffolds for controlled intravaginal antibiotic release

Bacterial vaginosis (BV) is a highly recurrent vaginal condition linked with many health complications. Topical antibiotic treatments for BV are challenged with drug solubility in vaginal fluid, lack of convenience and user adherence to daily treatment protocols, among other factors. 3D-printed scaffolds can provide sustained antibiotic delivery to the female reproductive tract (FRT). Silicone vehicles have been shown to provide structural stability, flexibility, and biocompatibility, with favorable drug release kinetics. This study formulates and characterizes novel metronidazole-containing 3D-printed silicone scaffolds for eventual application to the FRT. Scaffolds were evaluated for degradation, swelling, compression, and metronidazole release in simulated vaginal fluid (SVF). Scaffolds retained high structural integrity and sustained release. Minimal mass loss (<6%) and swelling (<2%) were observed after 14 days in SVF, relative to initial post-cure measurements. Scaffolds cured for 24 hr (50 °C) demonstrated elastic behavior under 20% compression and 4.0 N load. Scaffolds cured for 4 hr (50 °C), followed by 72 hr (4 °C), demonstrated the highest, sustained, metronidazole release (4.0 and 27.0 µg/mg) after 24 hr and 14 days, respectively. Based upon daily release profiles, it was observed that the 24 hr timepoint had the greatest metronidazole release of 4.08 μg/mg for scaffolds cured at 4 hr at 50 °C followed by 72 hr at 4 °C. For all curing conditions, release of metronidazole after 1 and 7 days showed > 4.0-log reduction in Gardnerella concentration. Negligible cytotoxicity was observed in treated keratinocytes comparable to untreated cells, This study shows that pressure-assisted microsyringe 3D-printed silicone scaffolds may provide a versatile vehicle for sustained metronidazole delivery to the FRT.

3D Printing Technology as a Promising Tool to Design Nanomedicine-Based Solid Dosage Forms: Contemporary Research and Future Scope.

3D printing technology in medicine is gaining great attention from researchers since the FDA approved the first 3D-printed tablet (Spritam®) on the market. This technique permits the fabrication of various types of dosage forms with different geometries and designs. Its feasibility in the design of different types of pharmaceutical dosage forms is very promising for making quick prototypes because it is flexible and does not require expensive equipment or molds. However, the development of multi-functional drug delivery systems, specifically as solid dosage forms loaded with nanopharmaceuticals, has received attention in recent years, although it is challenging for formulators to convert them into a successful solid dosage form. The combination of nanotechnology with the 3D printing technique in the field of medicine has provided a platform to overcome the challenges associated with the fabrication of nanomedicine-based solid dosage forms. Therefore, the major focus of the present manuscript is to review the recent research developments that involved the formulation design of nanomedicine-based solid dosage forms utilizing 3D printing technology. Utilization of 3D printing techniques in the field of nanopharmaceuticals achieved the successful transformation of liquid polymeric nanocapsules and liquid self-nanoemulsifying drug delivery systems (SNEDDS) to solid dosage forms such as tablets and suppositories easily with customized doses as per the needs of the individual patient (personalized medicine). Furthermore, the present review also highlights the utility of extrusion-based 3D printing techniques (Pressure-Assisted Microsyringe-PAM; Fused Deposition Modeling-FDM) to produce tablets and suppositories containing polymeric nanocapsule systems and SNEDDS for oral and rectal administration. The manuscript critically analyzes contemporary research related to the impact of various process parameters on the performance of 3D-printed solid dosage forms.

3D printed bilayer mucoadhesive buccal film of estradiol: Impact of design on film properties, release kinetics and predicted in vivo performance

Despite being an effective therapy for menopausal symptoms, the use of oral estrogen is associated with low bioavailability and serious adverse effects of venous thromboembolism. Individualized therapy has been recommended to maximize benefits and curb the adverse effects, but much has not been done in developing formulations that offer flexibility to personalize therapy. In the present study, we employed an innovative 3D printing technology to design and develop bi-layered estradiol film with different infill patterns with an aim of improving bioavailability and facilitating personalized treatment. Hydroxypropyl cellulose (HPC-H) based formulation exhibited suitable rheological properties and was used as a feedstock to fabricate estradiol films with different infill patterns namely honeycomb, rectangular and plain. The back layer was prepared from a hydroxyethyl cellulose-based formulation. The resulting films were subsequently characterized in terms of their physicochemical, mechanical, environmental impact, and release characteristics among others. Films with a plain infill pattern exhibited significantly higher % elongation break and tensile strength. The in vitro drug release study revealed the fastest drug release profile for rectangular infill (96 % within 4 h) and the slowest drug release was observed for the plain infill pattern (∼35 % within 4 h), highlighting the effect of the infill pattern on release kinetics. Films with honeycomb infill patterns were selected for further characterization based on mechanical and in vitro release properties. No interaction between components of the formulation was observed and the absence of crystallinity in the final product was confirmed by Differential Scanning Calorimetry (DSC) and X-Ray Powder Diffraction analyses (XRD). The force of adhesiveness for the film was 0.13 ± 0.03 N. The predicted AUC 0–4 h, Cmax, and Tmax were 144.85 ng·h/mL, 65.97 ng/mL, and 0.83 h for a film (honeycomb infill pattern) loaded with 1 mg of estradiol. The printing process of films with honeycomb and rectangular infill patterns was evaluated as “green” using the index of Greenness Assessment of Printed Pharmaceuticals (iGAPP) tool. Our finding demonstrates the development of bi-layered estradiol film using Pressure assisted microsyringe (PAM) 3D printing and the influence of infill patterns on release kinetics and mechanical properties. The fabricated film not only facilitates the move towards personalized medicine but could also improve the bioavailability of the drugs by bypassing the hepatic first-pass metabolism and decreasing wash-out by the saliva.

3D Printing of Dapagliflozin Containing Self-Nanoemulsifying Tablets: Formulation Design and In Vitro Characterization.

The 3D printing techniques have been explored extensively in recent years for pharmaceutical manufacturing and drug delivery applications. The current investigation aims to explore 3D printing for the design and development of a nanomedicine-based oral solid dosage form of a poorly water-soluble drug. A self-nanoemulsifying tablet formulation of dapagliflozin propanediol monohydrate was developed utilizing the semisolid pressure-assisted microsyringe (PAM) extrusion-based 3D printing technique. The developed formulation system consists of two major components (liquid and solid phase), which include oils (caproyl 90, octanoic acid) and co-surfactant (PEG 400) as liquid phase while surfactant (poloxamer 188) and solid matrix (PEG 6000) as solid-phase excipients that ultimately self-nanoemulsify as a drug encapsulated nanoemulsion system on contact with aqueous phase/gastrointestinal fluid. The droplet size distribution of the generated nanoemulsion from a self-nanoemulsifying 3D printed tablet was observed to be 104.7 ± 3.36 nm with polydispersity index 0.063 ± 0.024. The FT-IR analysis of the printed tablet revealed that no drug-excipients interactions were observed. The DSC and X-RD analysis of the printed tablet revealed that the loaded drug is molecularly dispersed in the crystal lattice of the tablet solid matrix and remains solubilized in the liquid phase of the printed tablet. SEM image of the drug-loaded self-nanoemulsifying tablets revealed that dapagliflozin propanediol monohydrate was completely encapsulated in the solid matrix of the printed tablet, which was further confirmed by SEM-EDS analysis. The in vitro dissolution profile of dapagliflozin-loaded self-nanoemulsifying tablet revealed an immediate-release drug profile for all three sizes (8 mm, 10 mm, and 12 mm) tablets, exhibiting >75.0% drug release within 20 min. Thus, this study has emphasized the capability of the PAM-based 3D printing technique to print a self-nanoemulsifying tablet dosage form with an immediate-release drug profile for poorly water-soluble drug.

Optimization of semisolid extrusion (pressure-assisted microsyringe)-based 3D printing process for advanced drug delivery application

3D printing of pharmaceutical formulations requires juggling between the material properties and the printing process to achieve the geometry of the 3D printed products with the desired dose and release. The purpose of the current investigation is to identify the material suitability for semisolid extrusion-based 3D printing of advanced drug delivery system. In this study, the semisolid extrusion-based 3D printing technique was optimized to print a controlled release shell as a vehicle/carrier for oral drug delivery system. The consistency of the printable paste was optimized by screening different solvents for the polymer of interest (cellulose acetate as optimum) to achieve the desired continuous and uniform extrudability behavior. The polarity of the solvent played important role in the selection of the suitable solvent for the optimization process. The nozzle shape (tapered tip as optimum) and the nozzle diameter (630 µm as optimum) were found to be also significantly influenced by extrusion behavior. The printing pressure (60 psi) and speed (4 mm/s) were optimized to reach the required rate of extrusion during the 3D printing process. The thickness and the width of the printed layers have contributed to the creation of the standard triangle language (STL) G-code for the printing of the 3D drug delivery system. It was found that the first printed layer deposited on a particular type of substrate plays a significant role to influence the spreadable behavior of extruded materials. Finally, the present study design proposes a rational guideline for the semisolid extrusion-based 3D printing of pharmaceutical products of specific interest for personalized medicine.

Pressure-assisted microsyringe 3D printing of oral films based on pullulan and hydroxypropyl methylcellulose

Oral films (OFs) continue to attract attention as drug delivery systems, particularly for pedatric and geriatric needs. However, immiscibility between different polymers limits the full potential of OFs from being explored. One example is pullulan (PUL), a novel biopolymer which often has to be blended with other polymers to reduce cost and alter its mechanical properties. In this study, the state-of-the-art in fabrication techniques, three-dimensional (3D) printing was used to produce hybrid film structures of PUL and hydroxypropyl methylcellulose (HPMC), which were loaded with caffeine as a model drug. 3D printing was used to control the spatial deposition of films. HPMC was found to increase the mean mechanical properties of PUL films, where the tensile strength, elastic modulus and elongation break increased from 8.9 to 14.5 MPa, 1.17 to 1.56 GPa and from 1.48% to 1.77%, respectively. In addition, the spatial orientation of the hybrid films was also explored to determine which orientation could maximize the mechanical properties of the hybrid films. The results revealed that 3D printing could modify the mechanical properties of PUL whilst circumventing the issues associated with immiscibility.

3D-Printing with precise layer-wise dose adjustments for paediatric use via pressure-assisted microsyringe printing

The establishment of 3D-printing as manufacturing process for oral solid dosage forms enables new options for the individualized medicine.The aim of this work was to develop a novel drug-printing model using pressure-assisted microsyringe (PAM) technology, which allows the precise dispensing of drug substances.Printed tablets with different numbers of layers, mimicking different doses for pediatric subgroups, were analyzed regarding mass variation, friability, thickness and disintegration time. Furthermore, the uniformity of dosage units and the dissolution behavior were investigated.Friability was <0.3% in all cases, which demonstrates the ability of PAM printing to manufacture robust solid dosage. Disintegration results showed the dependency of the disintegration on the number of layers and therefore on the compact mass of polymer. However, all tablets disintegrated within 3 min and fulfilled the requirements of immediate release tablets of the USP and orodispersible tablets according to the Ph. Eur. Results of uniformity dosage units confirmed the successful manufacturing of the intended individualized doses. Drug dissolution appeared to be dependent on the number of layers. An increase of layers resulted in a decrease of the drug release rate. Further, the drug release could be correlated to the surface area/volume (SA/V) ratio.

Investigation of semi-solid formulations for 3D printing of drugs after prolonged storage to mimic real-life applications

The implementation of tailor-made dosage forms is currently one of the biggest challenges in the health sector. Over the last years, different approaches have been introduced to provide an individual and precise dispensing of the appropriate dose of an active pharmaceutical ingredient (API). A more recent approach, which has been intensively researched in the last years, is 3D-printing of medicines.The aim of this work was to develop printing formulations free of organic solvents for a pressure-assisted microsyringe printing method (PAM), which should also be printable over several days of storage. Furthermore, the printed dosage forms should provide a sustained release of the incorporated API. A mixture of polyvinyl acetate/polyvinylpyrrolidone copolymer (PVAc-PVP), hydroxypropyl methylcellulose (HPMC) and highly dispersed silicon dioxide (SiO2) was found to be a feasible polymer matrix to achieve a sustained drug release. Levetiracetam (LEV) was used as model drug.The printed formulations were analyzed regarding mass variation, friability and thickness. Furthermore, the dissolution behavior of freshly printed tablets and tablets printed from stored printing formulations were investigated. The dissolution profiles indicate that the dissolution of LEV could be modified by varying the amount of HPMC and by changing the infill design of tablets. Tablet-like geometries with an infill design of 0.35 mm and 5% HPMC released 50% of the incorporated drug after 4 h, while for tablets with a higher HPMC amount the release was decreased (10% HPMC: 5.5 h; 15% HPMC: 8 h). All printed tablets exhibit a friability < 0.5%, indicating that PAM printing is suitable for the manufacturing of tablets with a high structural integrity. Furthermore, this study demonstrates the ability of producing tablets with a uniform content and mass using PAM printing.

Polymers for Extrusion-Based 3D Printing of Pharmaceuticals: A Holistic Materials-Process Perspective.

Three dimensional (3D) printing as an advanced manufacturing technology is progressing to be established in the pharmaceutical industry to overcome the traditional manufacturing regime of 'one size fits for all'. Using 3D printing, it is possible to design and develop complex dosage forms that can be suitable for tuning drug release. Polymers are the key materials that are necessary for 3D printing. Among all 3D printing processes, extrusion-based (both fused deposition modeling (FDM) and pressure-assisted microsyringe (PAM)) 3D printing is well researched for pharmaceutical manufacturing. It is important to understand which polymers are suitable for extrusion-based 3D printing of pharmaceuticals and how their properties, as well as the behavior of polymer–active pharmaceutical ingredient (API) combinations, impact the printing process. Especially, understanding the rheology of the polymer and API–polymer mixtures is necessary for successful 3D printing of dosage forms or printed structures. This review has summarized a holistic materials–process perspective for polymers on extrusion-based 3D printing. The main focus herein will be both FDM and PAM 3D printing processes. It elaborates the discussion on the comparison of 3D printing with the traditional direct compression process, the necessity of rheology, and the characterization techniques required for the printed structure, drug, and excipients. The current technological challenges, regulatory aspects, and the direction toward which the technology is moving, especially for personalized pharmaceuticals and multi-drug printing, are also briefly discussed.

3D Printing Technology in Customized Drug Delivery System: Current State of the Art, Prospective and the Challenges.

3D printing/Additive Manufacturing seems a pragmatic approach to realize the quest for a truly customized and personalized drug delivery. 3DP technology, with innovations in pharmaceutical development and an interdisciplinary approach to finding newer Drug Delivery Systems can usher a new era of treatments to various diseases. The true potential of this is yet to be realized, and the US-FDA is focusing on the regulatory science of 3D printed medical devices to help patients access this technology safely and effectively. The approval of the first 3D printed prescription medicine by FDA is a promising step in the translation of more research in this area. A web-search on PubMed, ScienceDirect, and Nature was performed with the keywords Customized 3D printing and Drug delivery, publications dealing with the aspects of drug delivery using 3D printing for personalized or customized delivery were further considered and analyzed and discussed. We present the advantages offered by 3DP over conventional methods of formulation development and discuss the current state of 3DP in pharmaceutics and how it can be used to develop a truly customized drug delivery system, various 3DP technologies including Stereolithography (SLA), Selective Laser Sintering (SLS), Fused Deposition Modelling (FDM), Pressure Assisted Microsyringe (PAM) that have been used to develop pharmaceutical products have been discussed along with their limitations and also the regulatory considerations to help formulation scientists envisaging research in this area with the necessary information. 3D printing has the potential to fabricate a customized drug delivery system. Presence of many drug formulation and the devices are already in the regulatory approval process indicating its success.

Structure-Based Gastro-Retentive and Controlled-Release Drug Delivery with Novel 3D Printing.

In the present contribution, the aim is to explore and establish a way in which 3D printing and gastro-retentive drug delivery systems (GRDDSs) are combined (focusing on inner structure innovation) to achieve extended and stable gastro-retention and controlled-release of drug. Three digital models diverse in construction were designed and substantialized by a pressure-assisted microsyringe (PAM) 3D printer. Preparations were characterized by means of DSC, XRD, FTIR, and SEM. In vitro buoyancy study and in vivo gamma scintigraphy method were conducted to validate gastro-retention property of these innovative preparations in vitro/in vivo respectively. Release kinetic model was established and release mechanism was discussed. Tablets manufactured under certain range of parameters (intersecting angle, full filling gap) were tight and accurate in shape. Tablets printed with specific parameters (full filling gap, 50%; nozzle extrusion speed, 0.006mm/s; layer height, 0.4mm; compensation value, 0.25; quantity of layers, 15; outline printing value, 2) exhibited satisfactory in vitro (10-12h)/in vivo (8-10h) retention ability and possessed stable 10-12h controlled-release quality. In general, 3D printing has tremendous advantage over conventional fabrication technique in intricate drug delivery systems and will be widely employed in pharmacy.

On-demand manufacturing of immediate release levetiracetam tablets using pressure-assisted microsyringe printing

Fast and accurate manufacturing of individually tailored solid dosage forms is one of the main challenges for personalized medicine. The use of 3D printers has recently been studied to determine their suitability for personalized drug manufacturing.In the current work, formulations free of organic solvents were developed for a pressure-assisted microsyringe printing method (PAM). The water soluble polymer polyvinyl alcohol-polyethylene glycol graft copolymer (PVA-PEG) was used as matrix, while levetiracetam (LEV) was used as model drug. Furthermore, the influence of a second polymer, polyvinylpyrrolidone-vinyl acetate copolymer (PVP-PVAc) on the properties of the printed tablets was investigated. Tablets were printed using a 3D-Bioplotter. The printed formulations were analyzed regarding mass variation, friability and thickness. Furthermore, the disintegration behavior and dissolution profile were analyzed. Investigations of the dissolution profiles of printed tablets show that an immediate release of the API could be achieved. For tablets with PVA-PEG the drug is released completely within 10 min while the additional use of PVP-PVAc leads to a slightly delay with a complete release within 20 min. The same trend is observed regarding the disintegration time of printed tablets. Tablets with PVA-PEG disintegrated within 95 ± 10 s while tablets with additional PVP-PVAc disintegrated within 130 ± 20 s.Friability of <0.5% indicate that the used PAM printing method provides tablets without loss of structural integrity during handling. Furthermore, it could be shown that the production of tablets with a good content uniformity using a 3D Bioplotter is suitable.

The control of stem cell morphology and differentiation using three-dimensional printed scaffold architecture.

In this work, we investigated the interactions of human mesenchymal stem cells (hMSCs) with three-dimensional (3D) printed scaffolds displaying different scaffold architectures. Pressure-assisted microsyringe system was used to fabricate scaffolds with square (SQR), hexagonal (HEX), and octagonal (OCT) architectures defined by various degrees of curvatures. OCT represents the highest degree of curvature followed by HEX, and SQR is composed of linear struts without curvature. Scaffolds were fabricated from poly(L-lactic acid) and poly(tyrosol carbonate). We found that hMSCs attached and spread by taking the shape of the individual struts, exhibiting high aspect ratios (ARs) and mean cell area when cultured on OCT scaffolds as compared with those cultured on HEX and SQR scaffolds. In contrast, cells appeared bulkier with low AR on SQR scaffolds. These significant changes in cell morphology directly correlate with the stem cell lineage commitment, such that 80 ± 1% of the hMSCs grown on OCT scaffolds differentiated into osteogenic lineage, compared with 70 ± 4% and 62 ± 2% of those grown on HEX and SQR scaffolds, respectively. Cells on OCT scaffolds also showed 2.5 times more alkaline phosphatase activity compared with cells on SQR scaffolds. This study demonstrates the importance of scaffold design to direct stem cell differentiation, and aids in the development of novel 3D scaffolds for bone regeneration.

A phase diagram for microfabrication of geometrically controlled hydrogel scaffolds

Hydrogels are considered as excellent candidates for tissue substitutes by virtue of their high water content and biphasic nature. However, the fact that they are soft, wet and floppy renders them difficult to process and use as custom-designed scaffolds. To address this problem alginate hydrogels were modeled and characterized by measuring stress–strain and creep behavior as well as viscosity as a function of sodium alginate concentration, cross-linking time and calcium ion concentration. The gels were then microfabricated into scaffolds using the pressure-assisted microsyringe. The mechanical and viscous characteristics were used to generate a processing window in the form of a phase diagram which describes the fidelity of the scaffolds as a function of the material and machine parameters. The approach can be applied to a variety of microfabrication methods and biomaterials in order to design well-controlled custom scaffolds.

Polyurethane unimorph bender microfabricated with Pressure Assisted Microsyringe (PAM) for biomedical applications

This paper describes a new microfabrication technique for bender-type electromechanical actuators made of an elastomeric electroactive polymer. The technique is based on a computer-controlled deposition of the active material with a microsyringe. The paper describes the developed microfabrication system and proposes a simple deposition model. The realization of solid-state unimorph bender actuators made of polyurethane as electrolyte and a mixture of carbon black and polyurethane as electrodes is presented. Prototype actuators fabricated both with the new technique were driven with electrical field of 100 V/μm and showed bending angles higher than 30°. In this way, we have demonstrated that it is possible to fabricate polyurethane based microactuators using a polyurethane/carbon black composite such as device.

Optimization of PAM Scaffolds for Neural Tissue Engineering: Preliminary Study on an SH-SY5Y Cell Line

Engineering neural tissue is one of the most challenging goals of tissue engineering. Neural tissue is highly complex and possesses an organized three-dimensional (3D) distribution that is essential for tissue function. An optimal scaffold for tissue engineering has to provide this distribution until the cells are able to activate their normal functions and develop neural connections with the host tissue. Different strategies such as gene therapy and cell transplantation particularly in retinal tissue have been tested, but so far they have only induced retinal degeneration in animals. The objective of this work was to study neural cell assembly as a function of scaffold features and surface chemistry for application in retinal tissue engineering using microfabricated patterns with a well-defined geometry. Because retinal neurons are known to be arranged in hexagonal arrays, hexagonal scaffolds of poly(DL-lactide-co-glycolide) acid were fabricated using a pressure-assisted microsyringe (PAM) system. The behavior of a model cell, neuroblastoma originating from human retina (SH-SY5Y), was analyzed after seeding on the scaffolds, measuring cell density as a function of line width and length of the scaffold to identify the optimal hexagonal geometry. We also evaluated the influence of scaffold on cell metabolism using the methyl thiazolyl tetrazolium assay and on neurite extension. As far as two-dimensional scaffolds are concerned, the results show that although metabolic activity per cell remains constant, hexagons with sides of 500 microm and line widths of 20 +/- 5 microm are optimum for neural cell adhesion in terms of cell density. On 3D scaffolds, cell metabolism is about three times higher than controls, and the optimum number of layers in the scaffold is three or four.