A once-a-month oral contraceptive

Prolongation of the gastric residence time of caffeine after administration in fed state: Comparison of effervescent granules with an extended release tablet

The aim of the present study was to investigate the gastroretentive capacity of different formulation principles. This was indirectly determined by the absorption behavior of caffeine from the dosage forms. A slow and continuous appearance of caffeine in the saliva of healthy volunteers was used as a parameter for a prolonged gastric retention time. For this purpose, a four-way study was conducted with twelve healthy volunteers using the following test procedures: (1) Effervescent granules with 240 mL of still water administered in fed state, (2) effervescent granules with 20 mL of still water in fed state, (3) extended release (ER) tablet with 240 mL of still water in fed state, and (4) effervescent granules with 240 mL of still water in fasted state. The initial rise of the caffeine concentrations was more pronounced after the intake of the effervescent granules in the fed state compared to that of the ER tablets. However, tmax tended to be shorter in the fed study arms following administration of the ER tablet compared to the granules. Overall, the application of active pharmaceutical ingredients formulated as effervescent granules seems to be a promising approach to increase their gastric residence time after intake in fed state.

Review article: Current status and future directions of ingestible electronic devices in gastroenterology

BACKGROUND

Advances in microelectronics have greatly expanded the capabilities and clinical potential of ingestible electronic devices.

AIM

To provide an overview of the structure and potential impact of ingestible devices in development that are relevant to the gastrointestinal tract.

METHODS

We performed a detailed literature search to inform this narrative review.

RESULTS

Technical success of ingestible electronic devices relies on the ability to miniaturise the microelectronic circuits, sensors and components for interventional functions while being sufficiently powered to fulfil the intended function. These devices offer the advantages of being convenient and minimally invasive, with real-time assessment often possible and with minimal interference to normal physiology. Safety has not been a limitation, but defining and controlling device location in the gastrointestinal tract remains challenging. The success of capsule endoscopy has buoyed enthusiasm for the concepts, but few ingestible devices have reached clinical practice to date, partly due to the novelty of the information they provide and also due to the challenges of adding this novel technology to established clinical paradigms. Nonetheless, with ongoing technological advancement and as understanding of their potential impact emerges, acceptance of such technology will grow. These devices have the capacity to provide unique insight into gastrointestinal physiology and pathophysiology. Interventional functions, such as sampling of tissue or luminal contents and delivery of therapies, may further enhance their ability to sharpen gastroenterological diagnoses, monitoring and treatment.

CONCLUSIONS

The development of miniaturised ingestible microelectronic-based devices offers exciting prospects for enhancing gastroenterological research and the delivery of personalised, point-of-care medicine.

Milk exosomes anchored with hydrophilic and zwitterionic motifs enhance mucus permeability for applications in oral gene delivery

Exosomes have emerged as a promising tool for the delivery of drugs and genetic materials, owing to their biocompatibility and non-immunogenic nature. However, challenges persist in achieving successful oral delivery due to their susceptibility to degradation in the harsh gastrointestinal (GI) environment and impeded transport across the mucus-epithelium barrier. To overcome these challenges, we have developed high-purity bovine milk exosomes (mExo) as a scalable and efficient oral drug delivery system, which can be customized by incorporating hydrophilic and zwitterionic motifs on their surface. In our study, we observed significantly improved transport rates by 2.5-4.5-fold in native porcine intestinal mucus after the introduction of hydrophilic and zwitterionic surface modifications, as demonstrated by transwell setup and fluorescence recovery after photobleaching (FRAP) analysis. Remarkably, mExo functionalized by a block peptide (BP), consisting of cationic and anionic amino acids arranged in blocks at the two ends, demonstrated superior tolerability in the acidic gastric environment (with a protein recovery rate of 84.8 ± 7.7%) and exhibited a 2.5-fold increase in uptake by intestinal epithelial cells. Furthermore, both mExo and mExo-BP demonstrated successful intracellular delivery of functional siRNA, resulting in up to 65% suppression of the target green fluorescence protein (GFP) gene expression at a low dose of siRNA (5 pmol) without causing significant toxicity. These findings highlight the immense potential of modifying mExo with hydrophilic and zwitterionic motifs for effective oral delivery of siRNA therapies.

Development of a multi-component gastroretentive expandable drug delivery system (GREDDS) for personalized administration of metformin

OBJECTIVES

Efficacy and compliance of type II diabetes treatment would greatly benefit from dosage forms providing controlled release of metformin in the upper gastrointestinal tract. In this respect, the feasibility of a new system ensuring stomach-retention and personalized release of this drug at its absorption window for multiple days was investigated.

METHODS

The system proposed comprised of a drug-containing core and a viscoelastic umbrella-like skeleton, which were manufactured by melt-casting and 3D printing. Prototypes, alone or upon assembly and insertion into commercially-available capsules, were characterized for key parameters: thermo-mechanical properties, accelerated stability, degradation, drug release, deployment performance, and resistance to simulated gastric contractions.

RESULTS

Each part of the system was successfully manufactured using purposely-selected materials and the performance of final prototypes matched the desired one. This included: i) easy folding of the skeleton against the core in the collapsed administered shape, ii) rapid recovery of the cumbersome configuration at the target site, even upon storage, and iii) prolonged release of metformin.

CONCLUSIONS

Composition, geometry, and performance of the system developed in this work were deemed acceptable for stomach-retention and prolonged as well as customizable release of metformin in its absorption window, laying promising bases for further development steps.

Intestinal retentive systems - recent advances and emerging approaches

Intestinal retentive devices (IRDs) are devices designed to anchor within the lumen of the intestines for long-term residence in the gastrointestinal tract. IRDs can enable impactful medical device technologies including sustained oral drug delivery systems, indwelling sensors, or real-time diagnostics. The design and testing of IRDs present a myriad of challenges, including precise deployment of the device at desired intestinal locations, secure anchoring within the gastrointestinal tract to allow for natural function, and safe removal of the IRD at user-defined times. Advancing the state-of-the-art of IRD is an interdisciplinary effort that requires innovations such as new materials, novel anchoring mechanisms, and medical device design with consistent input from clinical practitioners and end-users. This perspective briefly reviews the current state-of-the-art for IRDs and charts a path forward to inform the design of future concepts. Specifically, this article will highlight materials, retention mechanisms, and test beds to measure the efficacy of IRDs and their mechanisms. Finally, potential synergies between IRD and other medical device technologies are presented to identify future opportunities.

Modular Titratable Polypills for Personalized Medicine and Simplification of Complex Medication Regimens

Simplification of complex medication regimens in polypharmacy positively contributes to treatment adherence and cost-effective improved health outcomes. Even though fixed dose combination (FDC) drug products are the only currently available single dose poly-pill regimens, the lack of flexibility in dose adjustment of a single drug in the combination limits their efficacy. To fill the existing gap in drug dose personalization and simplification of complex medication regimens commonly encountered in the treatment of cardiovascular disease, tuberculosis, and tapering of corticosteroid therapy, a modular titratable polypill approach that simultaneously addresses both aspects is proposed. The polypill consists of modular units that contain different drugs at incremental or decremental doses to be assembled in a single titratable polypill at the required dose for each drug through a stacking or interlocking process. The variable dose (VD) modular tablets are subjected to quality control tests and found to comply to pharmacopeia's acceptance criteria and requirements specified in the respective drug monographs. A cost-effectiveness analysis is conducted supporting the VD strategy as cost-effective compared to the FDC strategy and more effective and less expensive than standard of care. The VD approach stands to enable pill burden reduction, ease of administration, enhancement of treatment adherence, and potential cost-saving benefits.

Enzyme-Triggered Intestine-Specific Targeting Adhesive Platform for Universal Oral Drug Delivery

Patient adherence to chronic therapies can be suboptimal, leading to poor therapeutic outcomes. Dosage forms that enable reduction in dosing frequency stand to improve patient adherence. Variation in gastrointestinal transit time, inter-individual differences in gastrointestinal physiology and differences in physicochemical properties of drugs represent challenges to the development of such systems. To this end, a small intestine-targeted drug delivery system is developed, where prolonged gastrointestinal retention and sustained release are achieved through tissue adhesion of drug pills mediated by an essential intestinal enzyme catalase. Here proof-of-concept pharmacokinetics is demonstrated in the swine model for two drugs, hydrophilic amoxicillin and hydrophobic levodopa. It is anticipated that this system can be applicable for many drugs with a diverse of physicochemical characteristics.

Untethered shape-changing devices in the gastrointestinal tract

INTRODUCTION

Advances in microfabrication, automation, and computer engineering seek to revolutionize small-scale devices and machines. Emerging trends in medicine point to smart devices that emulate the motility, biosensing abilities, and intelligence of cells and pathogens that inhabit the human body. Two important characteristics of smart medical devices are the capability to be deployed in small conduits, which necessitates being untethered, and the capacity to perform mechanized functions, which requires autonomous shape-changing.

AREAS COVERED

We motivate the need for untethered shape-changing devices in the gastrointestinal tract for drug delivery, diagnosis, and targeted treatment. We survey existing structures and devices designed and utilized across length scales from the macro to the sub-millimeter. These devices range from triggerable pre-stressed thin film microgrippers and spring-loaded devices to shape-memory and differentially swelling structures.

EXPERT OPINION

Recent studies demonstrate that when fully enabled, tether-free and shape-changing devices, especially at sub-mm scales, could significantly advance the diagnosis and treatment of GI diseases ranging from cancer and inflammatory bowel disease (IBD) to irritable bowel syndrome (IBS) by improving treatment efficacy, reducing costs, and increasing medication compliance. We discuss the challenges and possibilities associated with ensuring safe, reliable, and autonomous operation of these smart devices.

Magnetically Powered Chitosan Milliwheels for Rapid Translation, Barrier Function Rescue, and Delivery of Therapeutic Proteins to the Inflamed Gut Epithelium

Inflammatory bowel disease (IBD) is mediated by an overexpression of tumor necrosis factor-α (TNF) by mononuclear cells in the intestinal mucosa. Intravenous delivery of neutralizing anti-TNF antibodies can cause systemic immunosuppression, and up to one-third of people are non-responsive to treatment. Oral delivery of anti-TNF could reduce adverse effects; however, it is hampered by antibody degradation in the harsh gut environment during transit and poor bioavailability. To overcome these shortcomings, we demonstrate magnetically powered hydrogel particles that roll along mucosal surfaces, provide protection from degradation, and sustain the local release of anti-TNF. Iron oxide particles are embedded into a cross-linked chitosan hydrogel and sieved to produce 100-200 μm particles called milliwheels (m-wheels). Once loaded with anti-TNF, these m-wheels release 10 to 80% of their payload over 1 week at a rate that depends on the cross-linking density and pH. A rotating magnetic field induces a torque on the m-wheels that results in rolling velocities greater than 500 μm/s on glass and mucus-secreting cells. The permeability of the TNF-challenged gut epithelial cell monolayers was rescued in the presence of anti-TNF carrying m-wheels, which both neutralized the TNF and created an impermeable patch over leaky cell junctions. With the ability to translate over mucosal surfaces at high speed, provide sustained release directly to the inflamed epithelium, and provide barrier rescue, m-wheels demonstrate a potential strategy to deliver therapeutic proteins for the treatment of IBD.

Soft robot-enabled controlled release of oral drug formulations

The creation of highly effective oral drug delivery systems (ODDSs) has long been the main objective of pharmaceutical research. Multidisciplinary efforts involving materials, electronics, control, and pharmaceutical sciences encourage the development of robot-enabled ODDSs. Compared with conventional rigid robots, soft robots potentially offer better mechanical compliance and biocompatibility with biological tissues, more versatile shape control and maneuverability, and multifunctionality. In this paper, we first describe and highlight the importance of manipulating drug release kinetics, i.e. pharmaceutical kinetics. We then introduce an overview of state-of-the-art soft robot-based ODDSs comprising resident, shape-programming, locomotive, and integrated soft robots. Finally, the challenges and outlook regarding future soft robot-based ODDS development are discussed.

Expandable Drug Delivery Systems Based on Shape Memory Polymers: Impact of Film Coating on Mechanical Properties and Release and Recovery Performance

Retentive drug delivery systems (DDSs) are intended for prolonged residence and release inside hollow muscular organs, to achieve either local or systemic therapeutic goals. Recently, formulations based on shape memory polymers (SMPs) have gained attention in view of their special ability to recover a shape with greater spatial encumbrance at the target organ (e.g., urinary bladder or stomach), triggered by contact with biological fluids at body temperature. In this work, poly(vinyl alcohol) (PVA), a pharmaceutical-grade SMP previously shown to be an interesting 4D printing candidate, was employed to fabricate expandable organ-retentive prototypes by hot melt extrusion. With the aim of improving the mechanical resistance of the expandable DDS and slowing down relevant drug release, the application of insoluble permeable coatings based on either Eudragit^® RS/RL or Eudragit^® NE was evaluated using simple I-shaped specimens. The impact of the composition and thickness of the coating on the shape memory, swelling, and release behavior as well as on the mechanical properties of these specimens was thoroughly investigated and the effectiveness of the proposed strategy was demonstrated by the results obtained.

Biodegradable ring-shaped implantable device for intravesical therapy of bladder disorders

Intravesical instillation is an efficient drug delivery route for the local treatment of various urological conditions. Nevertheless, intravesical instillation is associated with several challenges, including pain, urological infection, and frequent clinic visits for catheterization; these difficulties support the need for a simple and easy intravesical drug delivery platform. Here, we propose a novel biodegradable intravesical device capable of long-term, local drug delivery without a retrieval procedure. The intravesical device is composed of drug encapsulating biodegradable polycaprolactone (PCL) microcapsules and connected by a bioabsorbable Polydioxanone (PDS) suture with NdFeB magnets in the end. The device is easily inserted into the bladder and forms a 'ring' shape optimized for maximal mechanical stability as informed by finite element analysis. In this study, inserted devices were retained in a swine model for 4 weeks. Using this device, we evaluated the system's capacity for delivery of lidocaine and resiquimod and demonstrated prolonged drug release. Moreover, a cost-effectiveness analysis supports device implementation compared to the standard of care. Our data support that this device can be a versatile drug delivery platform for urologic medications.

Administration strategies and smart devices for drug release in specific sites of the upper GI tract

Targeting the release of drugs in specific sites of the upper GI tract would meet local therapeutic goals, improve the bioavailability of specific drugs and help overcoming compliance-related limitations, especially in chronic illnesses of great social/economic impact and involving polytherapies (e.g. Parkinson's and Alzeimer's disease, tubercolosis, malaria, HIV, HCV). It has been traditionally pursued using gastroretentive (GR) systems, i.e. low-density, high-density, magnetic, adhesive and expandable devices. More recently, the interest towards oral administration of biologics has prompted the development of novel drug delivery systems (DDSs) provided with needles and able to inject different formulations in the mucosa of the upper GI tract and particularly of esophagus, stomach or small intestine. Besides comprehensive literature analysis, DDSs identified as smart devices in view of their high degree of complexity in terms of design, working mechanism, materials employed and manufacturing steps were discussed making use of graphic tools.

[Worldwide contraception]

The latest statistics concerning contraceptive use in the world have been published in 2019 by the United Nations. Among the 1.9 billion of women of reproductive age (15-49 years), 1.1 billion have a need for family planning. Among them, 190 millions are not using any contraception, although they wanted to avoid a pregnancy. There is a significant discrepancy among continents concerning the percentage of contraceptive use and the distribution of the different types of contraception. Female sterilization is the most widespread method of contraception since it represents 24% of all contraception methods used. Male condoms is used by 21% of couples. Thus, progress is still needed to disseminate effective, well tolerated and potentially reversible methods of contraception. Education of females, couples, medical and paramedical staff is one of the priority targets to improve contraception throughout the world.

Foundations of gastrointestinal-based drug delivery and future developments

Gastrointestinal-based drug delivery is considered the preferred mode of drug administration owing to its convenience for patients, which improves adherence. However, unique characteristics of the gastrointestinal tract (such as the digestive environment and constraints on transport across the gastrointestinal mucosa) limit the absorption of drugs. As a result, many medications, in particular biologics, still exist only or predominantly in injectable form. In this Review, we examine the fundamentals of gastrointestinal drug delivery to inform clinicians and pharmaceutical scientists. We discuss general principles, including the challenges that need to be overcome for successful drug formulation, and describe the unique features to consider for each gastrointestinal compartment when designing drug formulations for topical and systemic applications. We then discuss emerging technologies that seek to address remaining obstacles to successful gastrointestinal-based drug delivery.

Recent progress in advanced biomaterials for long-acting reversible contraception

Unintended pregnancy is a global issue with serious ramifications for women, their families, and society, including abortion, infertility, and maternal death. Although existing contraceptive strategies have been widely used in people's lives, there have not been satisfactory feedbacks due to low contraceptive efficacy and related side effects (e.g., decreased sexuality, menstrual cycle disorder, and even lifelong infertility). In recent years, biomaterials-based long-acting reversible contraception has received increasing attention from the viewpoint of fundamental research and practical applications mainly owing to improved delivery routes and controlled drug delivery. This review summarizes recent progress in advanced biomaterials for long-acting reversible contraception via various delivery routes, including subcutaneous implant, transdermal patch, oral administration, vaginal ring, intrauterine device, fallopian tube occlusion, vas deferens contraception, and Intravenous administration. In addition, biomaterials, especially nanomaterials, still need to be improved and prospects for the future in contraception are mentioned.

Effect of Mirena placement on reproductive hormone levels at different time intervals after artificial abortion

BACKGROUND

Improper methods of contraception greatly increase the risk of abortion, cervical or endometrial lesions, and the number of recurrent artificial abortions. These complications result in the deterioration of a patient’s outcome. Further, the proportion of artificial abortions is highest among unmarried females. Placement of an intrauterine device, such as the Mirena, after an artificial abortion may decrease the likelihood of an endometrial injury caused by recurrent abortions while significantly improving its contraceptive effects.

AIM

To discuss the effect of Mirena placement on reproductive hormone levels at different time points after an artificial abortion.

METHODS

Women (n = 119) undergoing an artificial abortion operation were divided into the study (n = 56) and control (n = 63) groups. In the study group, the Mirena was inserted immediately after the artificial abortion, whereas in the control group, it was inserted 4–7 d after the onset of the first menstrual cycle after abortion. All participants were followed-up for 6 mo to observe the continuation and expulsion rates and adverse reactions and to measure the levels of serum estradiol (E2), follicle stimulating hormone (FSH), and luteinizing hormone (LH).

RESULTS

The continuation rates were 94.64% and 93.65% in the study group and the control group, respectively. The expulsion rates were 1.79% and 3.17% in the study group and the control group, respectively. There was no statistically significant difference between the two groups (P > 0.05). There were also no statistically significant differences in the proportion of patients with bacterial vaginitis, trichomonas vaginitis, or cervicitis between the groups (P > 0.05). Six months after Mirena placement, E2 Levels were 45.50 ± 7.13 pg/mL and 42.91 ± 8.10 pg/mL, FSH 13.60 ± 3.24 mIU/mL and 14.54 ± 3.11 mIU/mL, and LH 15.11 ± 2.08 mIU/mL and 14.60 ± 3.55 mIU/mL in the study and control groups, respectively. There were no significant differences in hormone levels between the two groups (P > 0.05). There were also no statistically significant differences in the proportions of abnormal menstruation, prolonged menstruation, or pain during intercourse between the study and control groups after Mirena placement (P > 0.05). There were no statistically significant differences in uterine volume, sexual desire, sexual activity, or the sexual satisfaction score between the study and control groups before and after Mirena placement (P > 0.05).

CONCLUSION

Placement of a Mirena intrauterine device immediately after an artificial abortion does not increase the risk of adverse reactions and can help prevent endometrial injury caused by recurrent abortions.

Dynamic omnidirectional adhesive microneedle system for oral macromolecular drug delivery

Oral drug administration remains the preferred route for patients and health care providers. Delivery of macromolecules through this route remains challenging because of limitations imposed by the transport across the gastrointestinal epithelium and the dynamic and degradative environment. Here, we present the development of a delivery system that combines physical (microneedle) and nonphysical (enhancer) modes of drug delivery enhancement for a macromolecule in a large animal model. Inspired by the thorny-headed intestinal worm, we report a dynamic omnidirectional mucoadhesive microneedle system capable of prolonged gastric mucosa fixation. Moreover, we incorporate sodium N-[8-(2-hydroxybenzoyl) amino] caprylate along with semaglutide and demonstrate enhanced absorption in swine resistant to physical displacement in the gastric cavity. Meanwhile, we developed a targeted capsule system capable of deploying intact microneedle-containing systems. These systems stand to enable the delivery of a range of drugs through the generation and maintenance of a privileged region in the gastrointestinal tract.

Contraceptive Technology: Present and Future

Many sexually active, reproductive-aged persons capable of becoming pregnant use some method of contraception. To expand options for those desiring birth control, new choices include a vaginal ring, transdermal patch, progestin-only pill, and spermicide. Compared with currently available methods, additional technologies that are highly effective, easy to use, cost efficient, and well-tolerated lay on the horizon. During contraceptive counseling, patient choice, and reproductive autonomy should remain paramount.

Preferences of Persons with or at Risk for Hepatitis C for Long-Acting Treatments

BACKGROUND

Whereas safe, curative treatments for hepatitis C virus (HCV) have been available since 2015, there are still 58 million infected persons worldwide, and global elimination may require new paradigms. We sought to understand the acceptability of long-acting HCV treatment approaches.

METHODS

A cross-sectional, 43-question survey was administered to 1457 individuals with HCV or at risk of HCV at 28 sites in 9 countries to assess comparative interest in a variety of long-acting strategies in comparison to oral pills.

RESULTS

Among HCV-positive participants, 37.7% most preferred an injection, 5.6% an implant, and 6% a gastric residence device, as compared to 50.8% who stated they would most prefer taking 1 to 3 pills per day. When compared directly to taking pills, differences were observed in the relative preference for an injection based on age (p<0.001), location (p<0.001), and prior receipt of HCV treatment (p=0.005), but not sex. When an implant was compared to pills, greater preference was represented by women (p=0.01) and adults of younger ages (p=0.012 per 5 years). Among participants without HCV, 49.5% felt that injections are stronger than pills, and 34.7% preferred taking injections to pills. Among those at-risk participants who had received injectable medications in the past, 123 out of 137 (89.8%) expressed willingness to receive one in the future.

CONCLUSIONS

These data point to high acceptability of long-acting treatments, which for a substantial minority, might even be preferred to pills for the treatment of HCV infection. Long-acting treatments for HCV infection might contribute to global efforts to eliminate hepatitis C.

Gastrointestinal synthetic epithelial linings

Epithelial tissues line the organs of the body, providing an initial protective barrier as well as a surface for nutrient and drug absorption. Here, we identified enzymatic components present in the gastrointestinal epithelium that can serve as selective means for tissue-directed polymerization. We focused on the small intestine, given its role in drug and nutrient absorption and identified catalase as an essential enzyme with the potential to catalyze polymerization and growth of synthetic biomaterial layers. We demonstrated that the polymerization of dopamine by catalase yields strong tissue adhesion. We characterized the mechanism and specificity of the polymerization in segments of the gastrointestinal tracts of pigs and humans ex vivo. Moreover, we demonstrated proof of concept for application of these gastrointestinal synthetic epithelial linings for drug delivery, enzymatic immobilization for digestive supplementation, and nutritional modulation through transient barrier formation in pigs. This catalase-based approach to in situ biomaterial generation may have broad indications for gastrointestinal applications.

Milk exosomes with enhanced mucus penetrability for oral delivery of siRNA

Bovine milk-derived exosomes have recently emerged as a promising nano-vehicle for the encapsulation and delivery of macromolecular biotherapeutics. Here we engineer high purity bovine milk exosomes (mExo) with modular surface tunability for oral delivery of small interfering RNA (siRNA). We utilize a low-cost enrichment method combining casein chelation with differential ultracentrifugation followed by size exclusion chromatography, yielding mExo of high concentration and purity. Using in vitro models, we demonstrate that negatively charged hydrophobic mExos can penetrate multiple biological barriers to oral drug delivery. A hydrophilic polyethylene glycol (PEG) coating was introduced on the mExo surface via passive, stable hydrophobic insertion of a conjugated lipid tail, which significantly reduced mExo degradation in acidic gastric environment and enhanced their permeability through mucin by over 3× compared to unmodified mExo. Both mExo and PEG-mExo exhibited high uptake by intestinal epithelial cells and mediated functional intracellular delivery of siRNA, thereby suppressing the expression of the target green fluorescence protein (GFP) gene by up to 70%. We also show that cationic chemical transfection is significantly more efficient in loading siRNA into mExo than electroporation. The simplicity of isolating high purity mExo in high concentrations and equipping them with tunable surface properties, demonstrated here, paves way for the development of mExo as an effective, scalable platform technology for oral drug delivery of siRNA.

Engineered drug delivery devices to address Global Health challenges

There is a dire need for innovative solutions to address global health needs. Polymeric systems have been shown to provide substantial benefit to all sectors of healthcare, especially for their ability to extend and control drug delivery. Herein, we review polymeric drug delivery devices for vaccines, tuberculosis, and contraception.

Overcoming negatively charged tissue barriers: Drug delivery using cationic peptides and proteins

Negatively charged tissues are ubiquitous in the human body and are associated with a number of common diseases yet remain an outstanding challenge for targeted drug delivery. While the anionic proteoglycans are critical for tissue structure and function, they make tissue matrix dense, conferring a high negative fixed charge density (FCD) that makes drug penetration through the tissue deep zones and drug delivery to resident cells extremely challenging. The high negative FCD of these tissues is now being utilized by taking advantage of electrostatic interactions to create positively charged multi-stage delivery methods that can sequentially penetrate through the full thickness of tissues, create a drug depot and target cells. After decades of work on attempting delivery using strong binding interactions, significant advances have recently been made using weak and reversible electrostatic interactions, a characteristic now considered essential to drug penetration and retention in negatively charged tissues. Here we discuss these advances using examples of negatively charged tissues (cartilage, meniscus, tendons and ligaments, nucleus pulposus, vitreous of eye, mucin, skin), and delve into how each of their structures, tissue matrix compositions and high negative FCDs create barriers to drug entry and explore how charge interactions are being used to overcome these barriers. We review work on tissue targeting cationic peptide and protein-based drug delivery, compare and contrast drug delivery designs, and also present examples of technologies that are entering clinical trials. We also present strategies on further enhancing drug retention within diseased tissues of lower FCD by using synergistic effects of short-range binding interactions like hydrophobic and H-bonds that stabilize long-range charge interactions. As electrostatic interactions are incorporated into design of drug delivery materials and used as a strategy to create properties that are reversible, tunable and dynamic, bio-electroceuticals are becoming an exciting new direction of research and clinical work.

Zero-order drug delivery: State of the art and future prospects

Pharmaceutical drugs are an important part of the global healthcare system, with some estimates suggesting over 50% of the world's population takes at least one medication per day. Most drugs are delivered as immediate-release formulations that lead to a rapid increase in systemic drug concentration. Although these formulations have historically played an important role, they can be limited by poor patient compliance, adverse side effects, low bioavailability, or undesirable pharmacokinetics. Drug delivery systems featuring first-order release kinetics have been able to improve pharmacokinetics but are not ideal for drugs with short biological half-lives or small therapeutic windows. Zero-order drug delivery systems have the potential to overcome the issues facing immediate-release and first-order systems by releasing drug at a constant rate, thereby maintaining drug concentrations within the therapeutic window for an extended period of time. This release profile can be used to limit adverse side effects, reduce dosing frequency, and potentially improve patient compliance. This review covers strategies being employed to attain zero-order release or alter traditionally first-order release kinetics to achieve more consistent release before discussing opportunities for improving device performance based on emerging materials and fabrication methods.