Picoliter-volume inkjet printing into planar microdevice reservoirs for low-waste, high-capacity drug loading

Inkjet Printing of Pharmaceuticals

Inkjet printing (IJP) is an additive manufacturing process that selectively deposits ink materials, layer-by-layer, to create 3D objects or 2D patterns with precise control over their structure and composition. This technology has emerged as an attractive and versatile approach to address the ever-evolving demands of personalized medicine in the healthcare industry. Although originally developed for nonhealthcare applications, IJP harnesses the potential of pharma-inks, which are meticulously formulated inks containing drugs and pharmaceutical excipients. Delving into the formulation and components of pharma-inks, the key to precise and adaptable material deposition enabled by IJP is unraveled. The review extends its focus to substrate materials, including paper, films, foams, lenses, and 3D-printed materials, showcasing their diverse advantages, while exploring a wide spectrum of therapeutic applications. Additionally, the potential benefits of hardware and software improvements, along with artificial intelligence integration, are discussed to enhance IJP's precision and efficiency. Embracing these advancements, IJP holds immense potential to reshape traditional medicine manufacturing processes, ushering in an era of medical precision. However, further exploration and optimization are needed to fully utilize IJP's healthcare capabilities. As researchers push the boundaries of IJP, the vision of patient-specific treatment is on the horizon of becoming a tangible reality.

Influence of the Volatility of Solvent on the Reproducibility of Droplet Formation in Pharmaceutical Inkjet Printing

Drop-on-demand (DOD) inkjet printing enables exact dispensing and positioning of single droplets in the picoliter range. In this study, we investigate the long-term reproducibility of droplet formation of piezoelectric inkjet printed drug solutions using solvents with different volatilities. We found inkjet printability of EtOH/ASA drug solutions is limited, as there is a rapid forming of drug deposits on the nozzle of the printhead because of fast solvent evaporation. Droplet formation of c = 100 g/L EtOH/ASA solution was affected after only a few seconds by little drug deposits, whereas for c = 10 g/L EtOH/ASA solution, a negative affection was observed only after t = 15 min, while prominent drug deposits form at the printhead tip. Due to the creeping effect, the crystallizing structures of ASA spread around the nozzle but do not clog it necessarily. When there is a negative affection, the droplet trajectory is affected the most, while the droplet volume and droplet velocity are influenced less. In contrast, no formation of drug deposits could be observed for highly concentrated, low volatile DMSO-based drug solution of c = 100 g/L even after a dispensing time of t = 30 min. Therefore, low volatile solvents are preferable to highly volatile solvents to ensure a reproducible droplet formation in long-term inkjet printing of highly concentrated drug solutions. Highly volatile solvents require relatively low drug concentrations and frequent printhead cleaning. The findings of this study are especially relevant when high droplet positioning precision is desired, e.g., drug loading of microreservoirs or drug-coating of microneedle devices.

Micromolding of Thermoplastic Polymers for Direct Fabrication of Discrete, Multilayered Microparticles

Soft lithography provides a convenient and effective method for the fabrication of microdevices with uniform size and shape. However, formation of an embossed, connective film as opposed to discrete features has been an enduring shortcoming associated with soft lithography. Removing this residual layer requires additional postprocessing steps that are often incompatible with organic materials. This limits adaptation and widespread realization of soft lithography for broader applications particularly in drug discovery and drug delivery fields. A novel and versatile approach is demonstrated that enables fabrication of discrete, multilayered, fillable, and harvestable microparticles directly from any thermoplastic polymer, even at very high molecular weights. The approach, isolated microparticle replication via surface-segregating polymer blend mold, utilizes a random copolymer additive, designed with a highly fluorinated segment that, when blended with the mold's matrix, spontaneously orients to the surface conferring an extremely low surface energy and nonwetting properties to the template. The extremely nonwetting properties of the mold are further utilized to load soluble biologics directly into the built-in microwells in a rapid and efficient manner using an innovative screen-printing approach. It is believed that this approach holds promise for fabrication of large-array, 3D, complex microstructures, and is a significant step toward clinical translation of microfabrication technologies.

Printing Drugs onto Nails for Effective Treatment of Onychomycosis

Inkjet printing (IJP) is an emerging technology for the precision dosing of medicines. We report, for the first time, the printing of the antifungal drug terbinafine hydrochloride directly onto nails for the treatment of onychomycosis. A commercial cosmetic nail printer was modified by removing the ink from the cartridge and replacing it with an in-house prepared drug-loaded ink. The drug-loaded ink was designed so that it was comparable to the commercial ink for key printability properties. Linear drug dosing was shown by changing the lightness of the colour selected for printing (R² = 0.977) and by printing multiple times (R² = 0.989). The drug loads were measured for heart (271 µg), world (205 µg) and football (133 µg) shapes. A disc diffusion assay against Trpytophan rubrum showed inhibition of fungal growth with printed-on discs. In vitro testing with human nails showed substantial inhibition with printed-on nails. Hence, this is the first study to demonstrate the ability of a nail printer for drug delivery, thereby confirming its potential for onychomycosis treatment.

In vitro models to evaluate ingestible devices: Present status and current trends

Orally ingestible medical devices offer significant opportunity in the diagnosis and treatment of gastrointestinal conditions. Their development necessitates the use of models that simulate the gastrointestinal environment on both a macro and micro scale. An evolution in scientific technology has enabled a wide range of in vitro, ex vivo and in vivo models to be developed that replicate the gastrointestinal tract. This review describes the landscape of the existing range of in vitro tools that are available to characterize ingestible devices. Models are presented with details on their benefits and limitations with regards to the evaluation of ingestible devices and examples of their use in the evaluation of such devices is presented where available. The multitude of models available provides a suite of tools that can be used in the evaluation of ingestible devices that should be selected on the functionality of the device and the mechanism of its function.

Sensing technologies and experimental platforms for the characterization of advanced oral drug delivery systems

Complex and miniaturized oral drug delivery systems are being developed rapidly for targeted, controlled drug release and improved bioavailability. Standard analytical techniques are widely used to characterize i) drug carrier and active pharmaceutical ingredients before loading into a delivery device (to ensure the solid form), and ii) the entire drug delivery system during the development process. However, in light of the complexity and the size of some of these systems, standard techniques as well as novel sensing technologies and experimental platforms need to be used in tandem. These technologies and platforms are discussed in this review, with a special focus on passive delivery systems in size range from a few 100 µm to a few mm. Challenges associated with characterizing these systems and evaluating their effect on oral drug delivery in the preclinical phase are also discussed.

Hot punching for loading of biodegradable microcontainers with budesonide-Soluplus film

Micro-reservoir based drug delivery systems have the potential to provide targeted drug release locally in the intestine, i.e. at the inflamed areas of the intestine of patients with inflammatory bowel disease (IBD). In this study, microcontainers with a diameter of 300 µm and a height of 100 µm, asymmetrical geometry and the possibility to provide unidirectional release, are fabricated in the biodegradable polymer poly-ɛ-caprolactone (PCL) using hot punching. As a first step towards local treatment of IBD, a novel method for loading of microcontainers with the corticosteroid budesonide is developed. For this purpose, a budesonide-Soluplus drug-polymer film is prepared by spin coating and loaded into the microcontainer reservoirs using hot punching. The processing parameters are optimized to achieve a complete loading of a large number of containers in a single step. A poly(lactic-co-glycolic acid) (PLGA) 50:50 lid is subsequently applied by spray coating. Solid-state characterization indicates that the drug is in an amorphous state in the drug-polymer films and the in vitro drug release profile showed a 68% release over 10 h. The results demonstrate that hot punching can be employed both as a production and loading method for PCL microcontainers with the perspective of local treatment of IBD.

Consumer-Grade Inkjet Printer for Versatile and Precise Chemical Deposition

Two simple, mechanical modifications are introduced to a consumer-grade inkjet printer to greatly increase its applicability. First, roller isolation bars are added to unlock multiple prints on the same substrate without smearing. This enables printing on a diverse set of substrates (rigid, elastic, liquid, granular, and sticky). Second, spring loadings are added to increase the print precision up to 50-fold, which facilitates alignment to a pre-patterned substrate or between successive prints. Utilizing the expanded substrate compatibility and the increased print precision, we explore tunable loading of drug combinations into microdevices. This loading method has promising applications within point-of-care personalized medication. Furthermore, we show how inkjet printers with array-type printheads (in our case, 6 x 90 nozzles) allow for quasi-simultaneous loading of reactants into microfluidic systems. The ability to do a quasi-simultaneous introduction of chemicals may be particularly useful for studies of rapidly reacting systems of three or more reactants, where premature introduction can shift the initial conditions from the intended. We believe that our modifications to an affordable system will inspire researchers to explore the possibilities of inkjet printing even further.

Inkjet printing of small molecules, biologics, and nanoparticles

During the last decades, inkjet printing has emerged as a novel technology and attracted the attention of the pharmaceutical industry, as a potential method for manufacturing personalized and customizable dosage forms to deliver drugs. Commonly, the desired drug is dissolved or dispersed within the ink and then dispensed in various dosage forms. Using this approach, several studies have been conducted to load hydrophilic or poorly water-soluble small molecules onto the surface of different solid substrates, including films, tablets, microneedles, and smart data-enriched edible pharmaceuticals, using two-dimensional and three-dimensional inkjet printing methods, with high dose accuracy and reproducibility. Furthermore, biological drugs, such as peptides, proteins, growth factors, and plasmids, have also been evaluated with positive results, eliciting the expected biological response; nonetheless, minor changes in the structure of these compounds with significant impaired activity cannot be dismissed. Another strategy using inkjet printing is to disperse drug-loaded nanoscale particles in the ink liquid, such as nanosuspension, nanocomplexes, or nanoparticles, which have been explored with promising results. Although these favorable outcomes, the proper selection of ink constituents and the inkjet printer, the correlation of printing cycles and effectively printed doses, the stability studies of drugs within the ink and the optimal analysis of samples before and after the printing process are the main challenges for inkjet printing, and therefore, this review analyzes these aspects to assess the body of current literature and help to guide future investigations on this field.

High diversity droplet microfluidic libraries generated with a commercial liquid spotter

Droplet libraries consisting of many reagents encapsulated in separate droplets are necessary for applications of microfluidics, including combinatorial chemical synthesis, DNA-encoded libraries, and massively multiplexed PCR. However, existing approaches for generating them are laborious and impractical. Here, we describe an automated approach using a commercial array spotter. The approach can controllably emulsify hundreds of different reagents in a fraction of the time of manual operation of a microfluidic device, and without any user intervention. We demonstrate that the droplets produced by the spotter are similarly uniform to those produced by microfluidics and automate the generation of a ~ 2 mL emulsion containing 192 different reagents in ~ 4 h. The ease with which it can generate high diversity droplet libraries should make combinatorial applications more feasible in droplet microfluidics. Moreover, the instrument serves as an automated droplet generator, allowing execution of droplet reactions without microfluidic expertise.

Orally ingestible medical devices for gut engineering

Orally ingestible medical devices provide significant advancement for diagnosis and treatment of gastrointestinal (GI) tract-related conditions. From micro- to macroscale devices, with designs ranging from very simple to complex, these medical devices can be used for site-directed drug delivery in the GI tract, real-time imaging and sensing of gut biomarkers. Equipped with uni-direction release, or self-propulsion, or origami design, these microdevices are breaking the barriers associated with drug delivery, including biologics, across the GI tract. Further, on-board microelectronics allow imaging and sensing of gut tissue and biomarkers, providing a more comprehensive understanding of underlying pathophysiological conditions. We provide an overview of recent advances in orally ingestible medical devices towards drug delivery, imaging and sensing. Challenges associated with gut microenvironment, together with various activation/actuation modalities of medical devices for micromanipulation of the gut are discussed. We have critically examined the relationship between materials–device design–pharmacological responses with respect to existing regulatory guidelines and provided a clear roadmap for the future.

Linked optical and gene expression profiling of single cells at high-throughput

Single-cell RNA sequencing has emerged as a powerful tool for characterizing cells, but not all phenotypes of interest can be observed through changes in gene expression. Linking sequencing with optical analysis has provided insight into the molecular basis of cellular function, but current approaches have limited throughput. Here, we present a high-throughput platform for linked optical and gene expression profiling of single cells. We demonstrate accurate fluorescence and gene expression measurements on thousands of cells in a single experiment. We use the platform to characterize DNA and RNA changes through the cell cycle and correlate antibody fluorescence with gene expression. The platform's ability to isolate rare cell subsets and perform multiple measurements, including fluorescence and sequencing-based analysis, holds potential for scalable multi-modal single-cell analysis.

Combinatorial Antimicrobial Susceptibility Testing Enabled by Non-Contact Printing

We demonstrate the utility of non-contact printing to fabricate the mAST—an easy-to-operate, microwell-based microfluidic device for combinatorial antibiotic susceptibility testing (AST) in a point-of-care format. The wells are prefilled with antibiotics in any desired concentration and combination by non-contact printing (spotting). For the execution of the AST, the only requirements are the mAST device, the sample, and the incubation chamber. Bacteria proliferation can be continuously monitored by using an absorbance reader. We investigate the profile of resistance of two reference Escherichia coli strains, report the minimum inhibitory concentration (MIC) for single antibiotics, and assess drug–drug interactions in cocktails by using the Bliss independence model.

Three-dimensional printing for drug delivery devices: a state-of-the-art survey

Over the last several decades, 3D printing technology, which encompasses many different fabrication techniques, had emerged as a promising tool in many fields of production, including the pharmaceutical industry. Specifically, 3D printing may be advantageous for drug delivery systems, systems aiming to improve the pharmacokinetics of drugs. These advantages include the ease of designing complex shapes, printing of drugs on demand, tailoring dosage to the specific needs of the patient and enhancing the bioavailability of drugs. This paper reviews the most recent advancements in this field, presenting both the abilities and limitations of several promising 3D printing methods.

Microfabricated devices for oral drug delivery

Oral administration of drugs is most convenient for patients and therefore the ultimate goal when developing new medication. The physical barriers in the body, low pH of the stomach and degradation by enzymes in the gastrointestinal tract are a few of the obstacles to succeeding with oral drug delivery. Microfabricated devices show promise to overcome some of these hindrances and thereby improve the bioavailability of drugs after oral administration. There is an increasing focus on microfabricated oral drug delivery systems, and so far there have been three main groups of designs: patch-like structures, microcontainers and microwells. Here, we review the newest development in top-down microfabricated devices for oral drug delivery with coverage of the aspects of design, choice of material and fabrication techniques. Furthermore, the drug loading techniques and methods for testing are discussed. In addition, we discuss the future perspectives for microfabricated devices.