Polymers for extended-release administration

Bone scaffolds-based localized drugs delivery for osteosarcoma: current status and future perspective

A common malignant bone neoplasm in teenagers is Osteosarcoma. Chemotherapy, surgical therapy, and radiation therapy together comprise the usual clinical course of treatment for Osteosarcoma. While Osteosarcoma and other bone tumors are typically treated surgically, however, surgical resection frequently fails to completely eradicate tumors, and in turn becomes the primary reason for postoperative recurrence and metastasis, ultimately leading to a high rate of mortality. Patients still require radiation and/or chemotherapy after surgery to stop the spread of the tumor and its metastases, and both treatments have an adverse influence on the body's organ systems. In the postoperative management of osteosarcoma, bone scaffolds can load cargos (growth factors or drugs) and function as drug delivery systems (DDSs). This review describes the different kinds of bone scaffolds that are currently available and highlights key studies that use scaffolds as DDSs for the treatment of osteosarcomas. The discussion also includes difficulties and perspectives regarding the use of scaffold-based DDSs. The study may serve as a source for outlining efficient and secure postoperative osteosarcoma treatment plans.

Magnetically targeted lidocaine sustained-release microspheres: optimization, pharmacokinetics, and pharmacodynamic radius of effect

OBJECTIVE

This study aimed to optimize the formulation of magnetically targeted lidocaine microspheres, reduce the microsphere particle size, and increase the drug loading and encapsulation rate of lidocaine. The optimized microspheres were characterized, and their pharmacokinetics and effective radii of action were studied.

METHODS

The preparation of magnetically targeted lidocaine microspheres was optimized using ultrasonic emulsification-solvent evaporation. The Box-Behnken design method and response surface method were used for optimization. The optimized microspheres were characterized and tested for their in vitro release. Blood concentrations were analyzed using a non-compartment model, and the main pharmacokinetic parameters (half-life (t1/2 ), maximum blood concentration, area under the blood concentration-time curve (AUC), time to peak (Tmax ), and mean retention time (MRT) were calculated. Pathological sections were stained to study the safety of the microsphere tissues. A rabbit sciatic nerve model was used to determine the "standard time (t0 )" and effective radius of the microspheres.

RESULTS

The optimized lidocaine microspheres exhibited significantly reduced particle size and increased drug loading and encapsulation rates. Pharmacokinetic experiments showed that the t1/2 , Tmax , and MRT of magnetically targeted lidocaine microspheres were significantly prolonged in the magnetic field, and the AUC0-48 and AUC0-∞ were significantly decreased. Its pharmacodynamic radius was 31.47 mm.

CONCLUSION

Magnetically targeted lidocaine microspheres provide sustained long-lasting release, neurotargeting, nerve blocking, and high tissue safety. This preparation has a significantly low blood concentration and a slow release in vivo, which can reduce local anesthetic entry into the blood. This may be a novel and effective method for improving postoperative comfort and treating chronic pain. This provides a countermeasure for exploring the size of the magnetic field for the application of magnetic drug-carrying materials.

Thermosensitive polymer prodrug nanoparticles prepared by an all-aqueous nanoprecipitation process and application to combination therapy

Despite their great versatility and ease of functionalization, most polymer-based nanocarriers intended for use in drug delivery often face serious limitations that can prevent their clinical translation, such as uncontrolled drug release and off-target toxicity, which mainly originate from the burst release phenomenon. In addition, residual solvents from the formulation process can induce toxicity, alter the physico-chemical and biological properties and can strongly impair further pharmaceutical development. To address these issues, we report polymer prodrug nanoparticles, which are prepared without organic solvents via an all-aqueous formulation process, and provide sustained drug release. This was achieved by the "drug-initiated" synthesis of well-defined copolymer prodrugs exhibiting a lower critical solution temperature (LCST) and based on the anticancer drug gemcitabine (Gem). After screening for different structural parameters, prodrugs based on amphiphilic diblock copolymers were formulated into stable nanoparticles by all-aqueous nanoprecipitation, with rather narrow particle size distribution and average diameters in the 50-80 nm range. They exhibited sustained Gem release in human serum and acetate buffer, rapid cellular uptake and significant cytotoxicity on A549 and Mia PaCa-2 cancer cells. We also demonstrated the versatility of this approach by formulating Gem-based polymer prodrug nanoparticles loaded with doxorubicin (Dox) for combination therapy. The dual-drug nanoparticles exhibited sustained release of Gem in human serum and acidic release of Dox under accelerated pathophysiological conditions. Importantly, they also induced a synergistic effect on triple-negative breast cancer line MDA-MB-231, which is a relevant cell line to this combination.

Designing an antimicrobial film for wound applications incorporating bacteriophages and ε-poly-l-lysine

Alginate-based dressings have been shown to promote wound healing, leveraging the unique properties of alginate. This work aimed to develop and characterize flexible individual and bilayered films to deliver bacteriophages (phages) and ε-Poly-l-lysine (ε-PLL). Films varied in different properties. The moisture content, swelling and solubility increased with higher alginate concentrations. The water vapour permeability, crucial in biomedical films to balance moisture levels for effective wound healing, reached optimal levels in bilayer films, indicating these will be able to sustain an ideal moist environment. The bilayer films showed improved ductility (lower tensile strength and increased elongation at break) compared to individual films. The incorporated phages maintained viability for 12 weeks under vacuum and refrigerated conditions, and their release was sustained and gradual. Antibacterial immersion tests showed that films with phages and ε-PLL significantly inhibited Pseudomonas aeruginosa PAO1 growth (>3.1 Log CFU/cm2). Particle release was influenced by the swelling degree and diffusional processes within the polymer network, providing insights into controlled release mechanisms for particles of varying size (50 nm to 6 μm) and charge. The films developed, demonstrated modulated release capabilities for active agents, and may show potential as controlled delivery systems for phages and wound healing adjuvants.

A Novel Intrauterine Device for the Spatio-Temporal Release of Norethindrone Acetate as a Counter-Estrogenic Intervention in the Genitourinary Syndrome of Menopause

The genitourinary syndrome of menopause (GSM) is a widely occurring condition affecting millions of women worldwide. The current treatment of GSM involves the use of orally or vaginally administered estrogens, often with the risk of endometrial hyperplasia. The utilization of progestogens offers a means to counteract the effects of estrogen on the endometrial tissue, decreasing unwanted side effects and improving therapeutic outcomes. In this study, a norethindrone acetate (NETA)-loaded, hollow, cylindrical, and sustained release platform has been designed, fabricated, and optimized for implantation in the uterine cavity as a counter-estrogenic intervention in the treatment of GSM. The developed system, which comprises ethyl cellulose (EC) and polycaprolactone (PCL), has been statistically optimized using a two-factor, two-level factorial design, with the mechanical properties, degradation, swelling, and in vitro drug release of NETA from the device evaluated. The morphological characteristics of the platform were further investigated through scanning electron microscopy in addition to cytocompatibility studies using NIH/3T3 cells. Results from the statistical design highlighted the platform with the highest NETA load and the EC-to-PCL ratio that exhibited favorable release and weight loss profiles. The drug release data for the optimal formulation were best fitted with the Peppas-Sahlin model, implicating both diffusion and polymer relaxation in the release mechanism, with cell viability results noting that the prepared platform demonstrated favorable cytocompatibility. The significant findings of this study firmly establish the developed platform as a promising candidate for the sustained release of NETA within the uterine cavity. This functionality serves as a counter-estrogenic intervention in the treatment of GSM, with the platform holding potential for further advanced biomedical applications.

Targeted Clindamycin Delivery Systems: Promising Options for Preventing and Treating Bacterial Infections Using Biomaterials

Targeted therapy represents a real opportunity to improve the health and lives of patients. Developments in this field are confirmed by the fact that the global market for drug carriers was worth nearly $40 million in 2022. For this reason, materials engineering and the development of new drug carrier compositions for targeted therapy has become a key area of research in pharmaceutical drug delivery in recent years. Ceramics, polymers, and metals, as well as composites, are of great interest, as when they are appropriately processed or combined with each other, it is possible to obtain biomaterials for hard tissues, soft tissues, and skin applications. After appropriate modification, these materials can release the drug directly at the site requiring a therapeutic effect. This brief literature review characterizes routes of drug delivery into the body and discusses biomaterials from different groups, options for their modification with clindamycin, an antibiotic used for infections caused by aerobic and anaerobic Gram-positive bacteria, and different methods for the final processing of carriers. Examples of coating materials for skin wound healing, acne therapy, and bone tissue fillers are given. Furthermore, the reasons why the use of antibiotic therapy is crucial for a smooth and successful recovery and the risks of bacterial infections are explained. It was demonstrated that there is no single proven delivery scheme, and that the drug can be successfully released from different carriers depending on the destination.

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.

Retrospective analysis of the biopharmaceutics characteristics of solid oral Modified-Release drug products in approved US FDA NDAs designated as Extended-Release or Delayed-Release formulations

BACKGROUND

Modified Release (MR) orally administered drugs products [Extended-Release (ER) and Delayed-Release (DR)] differ from Immediate-Release (IR) drug products in their drug release site and/or rate to offer therapeutic advantages. It is important to understand the biopharmaceutics factors that determine how a drug works in the gastrointestinal tract and the various pharmacokinetic properties that determine a drug's rate of absorption and release in the human body. To better understand the biopharmaceutics characteristics of ER and DR drug products, this study retrospectively analyzed submissions approved by the US Food and Drug Administration (FDA), from 2001 to 2021, and their corresponding review documents. This review work is expected to enhance the readers' understanding regarding the biopharmaceutics properties that supported approval of these products' ER claims, as per 21 CFR 320.25(f), and DR claims.

METHODS

A comprehensive search was conducted using the FDA's internal New Drug Application (NDA) database for ER and DR oral drug products approved between 2001 and 2021. The search yielded 87 ER applications (23 ER capsules and 64 ER tablets) and 21 DR applications (10 DR capsules, 11 DR tablets) for which electronic records were accessible. These products were analyzed for overall drug product design, dosing frequency compared to the reference (if applicable), degree of fluctuation, dissolution method, and alcohol dose-dumping.

RESULTS

Out of 87 total applications for ER drug products that were assessed, 62% of the ER tablets contained a polymer matrix formulation, and hypromellose (HPMC) was used in 50% of these products. 52% of the ER capsules consisted of polymer beads while about half of the DR drug products contained a non-bead formulation with a combination of polymers. The majority of ER drug products were found to have a reduction in dosing frequency and a decrease in the degree of fluctuation when compared to the IR reference product. The 13 ER drug products that exhibited an increase in degree of fluctuation exhibited general and pharmacodynamic benefits, such as reduced dosing frequency and reduced pill burden. The majority of DR formulations were developed to prevent drug degradation in the stomach, followed by to decrease potential stomach irritation, and lastly for localized release in the colon. The majority of ER drug products had 1:1 ratios of dissolution duration compared to dosing frequency (i.e., the majority of ER drug products had a dissolution duration of 24 h and were dosed every 24 h while those with a dissolution duration of 12 h were dosed every 12 h). The majority of ER applications had single-stage dissolution methods while most DR drug products used biphasic dissolution methods. All of the DR dissolution methods incorporated an acid stage of 2 h and a buffer stage with various timeframes. 53% the DR drug products had a ratio of dissolution duration to dosing frequency of 1:4 (e.g. a dissolution duration of 2 h to a dosing frequency of 8 h) or 1:8 (e.g. a dissolution duration of 2 h to a dosing frequency of 16 h). Of the ER tablets and DR drug products, 72% exhibited no alcohol dose-dumping under in vitro testing conditions. ER capsules, however, did not yield similar results-most of which exhibited alcohol induced dose-dumping. Alcohol dose dumping was mitigated by either in vivo studies or warnings on the drug product label.

CONCLUSION

The results of this study help the reader understand the design, characteristics, and pharmacological advantages of the ER and DR drug products for patient benefit; as well as the regulations governing the FDA's assessment of ER claims.

Starch-based materials for drug delivery in the gastrointestinal tract-A review

Starch is a natural copolymer with unique physicochemical characteristics. Historically, it has been physically, chemically, or enzymatically modified to obtain ad-hoc functional properties for its use in different applications. In this context, the use of starch-based materials in drug delivery systems (DDSs) has gained great attention mainly because it is cheap, biodegradable, biocompatible, and renewable. This paper reviews the state of the art in starch-based materials design for their use in drug-controlled release with internal stimulus responsiveness; i.e., pH, temperature, colonic microbiota, or enzymes; specifically, those orally administered for its release in the gastrointestinal tract (GIT). Physical-chemical principles in the design of these materials taking into account their response to a particular stimulus are discussed. The relationship between the type of DDSs structure, starch modification routes, and the corresponding drug release profiles are systematically analyzed. Furthermore, the challenges and prospects of starch-based materials for their use in stimulus-responsive DDSs are also debated.

pH-temperature Responsive Hydrogel-Mediated Delivery of Exendin-4 Encapsulated Chitosan Nanospheres for Sustained Therapeutic Efficacy in Type 2 Diabetes Mellitus

Type 2 Diabetes Mellitus (T2D) is a chronic, obesity-related, and inflammatory disorder characterize by insulin resistance, inadequate insulin secretion, hyperglycemia, and excessive glucagon secretion. Exendin-4 (EX), a clinically established antidiabetic medication that acts as a glucagon-like peptide-1 receptor agonist, is effective in lowering glucose levels and stimulating insulin secretion while significantly reducing hunger. However, the requirement for multiple daily injections due to EX's short half-life is a significant limitation in its clinical application, leading to high treatment costs and patient inconvenience. To address this issue, an injectable hydrogel system is developed that can provide sustained EX release at the injection site, reducing the need for daily injections. In this study, the electrospray technique is examine to form EX@CS nanospheres by electrostatic interaction between cationic chitosan (CS) and negatively charged EX. These nanospheres are uniformly dispersed in a pH-temperature responsive pentablock copolymer, which forms micelles and undergoes sol-to-gel transition at physiological conditions. Following injection, the hydrogel gradually degraded, exhibiting excellent biocompatibility. The EX@CS nanospheres are subsequently released, maintaining therapeutic levels for over 72 h compared to free EX solution. The findings demonstrate that the pH-temperature responsive hydrogel system containing EX@CS nanospheres can be a promising platform for the treatment of T2D.

A Magnetic Bio-Inspired Soft Carrier as a Temperature-Controlled Gastrointestinal Drug Delivery System

Currently, gastrointestinal bleeding in the colon wall and the small bowel is diagnosed and treated with endoscopes. However, the locations of this condition are often problematic to treat using traditional flexible and tethered tools. New studies commonly consider untethered devices for solving this problem. However, there still exists a gap in the extant literature, and more research is needed to diagnose and deliver drugs in the lower gastrointestinal tract using soft robotic carriers. This paper discusses the development of an untethered, magnetically-responsive bio-inspired soft carrier. A molding process is utilized to produce prototypes from Diisopropylidene-1,6-diphenyl-1,6-hexanediol-based Polymer with Ethylene Glycol Dimethacrylate (DiAPLEX) MP-3510 - a shape memory polymer with a low transition temperature to enable the fabrication of these carriers. The soft carrier design is validated through simulation results of deformation caused by magnetic elements embedded in the carrier in response to an external field. The thermal responsiveness of the fabricated prototype carriers is assessed ex vivo and in a phantom. The results indicate a feasible design capable of administering drugs to a target inside a phantom of a large intestine. The soft carrier introduces a method for the controlled release of drugs by utilizing the rubbery modulus of the polymer and increasing the recovery force through magnetic actuation.

Application of Biomedical Microspheres in Wound Healing

Tissue injury, one of the most common traumatic injuries in daily life, easily leads to secondary wound infections. To promote wound healing and reduce scarring, various kinds of wound dressings, such as gauze, bandages, sponges, patches, and microspheres, have been developed for wound healing. Among them, microsphere-based tissue dressings have attracted increasing attention due to the advantage of easy to fabricate, excellent physicochemical performance and superior drug release ability. In this review, we first introduced the common methods for microspheres preparation, such as emulsification-solvent method, electrospray method, microfluidic technology as well as phase separation methods. Next, we summarized the common biomaterials for the fabrication of the microspheres including natural polymers and synthetic polymers. Then, we presented the application of the various microspheres from different processing methods in wound healing and other applications. Finally, we analyzed the limitations and discussed the future development direction of microspheres in the future.

Reaching new lights: a review on photo-controlled nanomedicines and their in vivo evaluation

The selective and efficient delivery of bioactive molecules to sites of interest remains a formidable challenge in medicine. In recent years, it has been shown that stimuli-responsive drug delivery systems display several advantages over traditional drug administration such as an improved pharmacokinetic profile and the desirable ability to gain control over release. Light emerged as one of the most powerful stimuli due to its high biocompatibility, spatio-temporal control, and non-invasiveness. On the road to clinical translation, various chemical systems of high complexity have been reported with the aim to improve efficacy, safety, and versatility of drug delivery under complex biological conditions. For future research on the chemical design of such photo-controlled nanomedicines, it is essential to gain an understanding of their in vivo translation and efficiency. Here, we discuss photo-controlled nanomedicines that have been evaluated in vivo and provide an overview of the state-of-the-art that should guide future research design.

Reduced Cardiotoxicity of Ponatinib-Loaded PLGA-PEG-PLGA Nanoparticles in Zebrafish Xenograft Model

Tyrosine kinase inhibitors (TKIs) are the new generation of anti-cancer drugs with high potential against cancer cells’ proliferation and growth. However, TKIs are associated with severe cardiotoxicity, limiting their clinical value. One TKI that has been developed recently but not explored much is Ponatinib. The use of nanoparticles (NPs) as a better therapeutic agent to deliver anti-cancer drugs and reduce their cardiotoxicity has been recently considered. In this study, with the aim to reduce Ponatinib cardiotoxicity, Poly(D,L-lactide-co-glycolide)-b-poly(ethyleneoxide)-b-poly(D,L-lactide-co-glycolide) (PLGA-PEG-PLGA) triblock copolymer was used to synthesize Ponatinib in loaded PLGA-PEG-PLGA NPs for chronic myeloid leukemia (CML) treatment. In addition to physicochemical NPs characterization (NPs shape, size, size distribution, surface charge, dissolution rate, drug content, and efficacy of encapsulation) the efficacy and safety of these drug-delivery systems were assessed in vivo using zebrafish. Zebrafish are a powerful animal model for investigating the cardiotoxicity associated with anti-cancer drugs such as TKIs, to determine the optimum concentration of smart NPs with the least side effects, and to generate a xenograft model of several cancer types. Therefore, the cardiotoxicity of unloaded and drug-loaded PLGA-PEG-PLGA NPs was studied using the zebrafish model by measuring the survival rate and cardiac function parameters, and therapeutic concentration for in vivo efficacy studies was optimized in an in vivo setting. Further, the efficacy of drug-loaded PLGA-PEG-PLGA NPs was tested on the zebrafish cancer xenograft model, in which human myelogenous leukemia cell line K562 was transplanted into zebrafish embryos. Our results demonstrated that the Ponatinib-loaded PLGA-PEG-PLGA NPs at a concentration of 0.001 mg/mL are non-toxic/non-cardio-toxic in the studied zebrafish xenograft model.

Considerations for Polymers Used in Ocular Drug Delivery

PURPOSE

Age-related eye diseases are becoming more prevalent. A notable increase has been seen in the most common causes including glaucoma, age-related macular degeneration (AMD), and cataract. Current clinical treatments vary from tissue replacement with polymers to topical eye drops and intravitreal injections. Research and development efforts have increased using polymers for sustained release to the eye to overcome treatment challenges, showing promise in improving drug release and delivery, patient experience, and treatment compliance. Polymers provide unique properties that allow for specific engineered devices to provide improved treatment options. Recent work has shown the utilization of synthetic and biopolymer derived biomaterials in various forms, with this review containing a focus on polymers Food and Drug Administration (FDA) approved for ocular use.

METHODS

This provides an overview of some prevalent synthetic polymers and biopolymers used in ocular delivery and their benefits, brief discussion of the various types and synthesis methods used, and administration techniques. Polymers approved by the FDA for different applications in the eye are listed and compared to new polymers being explored in the literature. This article summarizes research findings using polymers for ocular drug delivery from various stages: laboratory, preclinical studies, clinical trials, and currently approved. This review also focuses on some of the challenges to bringing these new innovations to the clinic, including limited selection of approved polymers.

RESULTS

Polymers help improve drug delivery by increasing solubility, controlling pharmacokinetics, and extending release. Several polymer classes including synthetic, biopolymer, and combinations were discussed along with the benefits and challenges of each class. The ways both polymer synthesis and processing techniques can influence drug release in the eye were discussed.

CONCLUSION

The use of biomaterials, specifically polymers, is a well-studied field for drug delivery, and polymers have been used as implants in the eye for over 75 years. Promising new ocular drug delivery systems are emerging using polymers an innovative option for treating ocular diseases because of their tunable properties. This review touches on important considerations and challenges of using polymers for sustained ocular drug delivery with the goal translating research to the clinic.

Advances in the therapeutic delivery and applications of functionalized Pluronics: A critical review

Pluronic (PEO-PPO-PEO) block copolymers can form nano-sized micelles with a structure composed of a hydrophobic PPO core and hydrophilic PEO shell layer. Pluronics are U.S. Food and Drug Administration approved polymers, which are widely used for solubilization of drugs and their delivery, gene/therapeutic delivery, diagnostics, and tissue engineering applications due to their non-ionic properties, non-toxicity, micelle forming ability, excellent biocompatibility and biodegradability. Although Pluronics have been employed as drug carrier systems for several decades, numerous issues such as rapid dissolution, shorter residence time in biological media, fast clearance and weak mechanical strength have hindered their efficacy. Pluronics have been functionalized with pH-sensitive, biological-responsive moieties, antibodies, aptamers, folic acid, drugs, different nanoparticles, and photo/thermo-responsive hydrogels. These functionalization strategies enable Pluronics to act as stimuli responsive and targeted drug delivery vehicles. Moreover, Pluronics have emerged in nano-emulsion formulations and have been utilized to improve the properties of cubosomes, dendrimers and nano-sheets, including their biocompatibility and aqueous solubility. Functionalization of Pluronics results in the significant improvement of target specificity, loading capacity, biocompatibility of nanoparticles and stimuli responsive hydrogels for the promising delivery of a range of drugs. Therefore, this review presents an overview of all advancements (from the last 15 years) in functionalized Pluronics, providing a valuable tool for industry and academia in order to optimize their use in drug or therapeutic delivery, in addition to several other biomedical applications.

Preparation, Characterization, and Selection of Optimal Forms of (S)-Carvedilol Salts for the Development of Extended-Release Formulation

(S)-carvedilol (S-CAR) is the dominant pharmacodynamic conformation of carvedilol, but its further development for extended-release formulation is restricted by its poor solubility. This study aimed to prepare and screen S-CAR salts that could be used to improve solubility and allow extended release. Five salts of S-CAR with well-known acid counterions (i.e., phosphate, hydrochloride, sulfate, fumarate, and tartrate) were produced using similar processes. However, these salts were obtained with water contents of 1.60-12.28%, and their physicochemical properties differed. The melting points of phosphate, hydrochloride, and tartrate were 1.1-1.5 times higher than that of the free base. The solubility of S-CAR salts was promoted to approximately 3-32 times higher than that of the free base at pH 5.0-8.0. Typical pH-dependent solubilities were evidently observed in S-CAR salts, but considerable differences in solubility properties among these salts were observed. S-CAR phosphate and hydrochloride possessed high melting points, considerable solubility, and excellent chemical and crystallographic stabilities. Accordingly, S-CAR phosphate and hydrochloride were chosen for further pharmacokinetic experiments and pharmaceutical study. S-CAR phosphate and hydrochloride extended-release capsules were prepared using HPMC K15 as the matrix and presented extended release in in vitro and in vivo evaluations. Results implied that water molecules in the hydrated salt were a potential threat to the achievement of crystal stability and thermostability. S-CAR phosphate and hydrochloride are suitable for further development of the extended-release formulation.

Oral Drug Delivery: Conventional to Long Acting New-Age Designs

The Oral route of administration forms the heartwood of the ever-growing tree of drug delivery technology. It is one of the most preferred dosage forms among patients and controlled release community. Despite the high patient compliance, the deliveries of anti-cancerous drugs, vaccines, proteins, etc. via the oral route are limited and have recorded a very low bioavailability. The oral administration must overcome the physiological barriers (low solubility, permeation and early degradation) to achieve efficient and sustained delivery. This review aims at highlighting the conventional and modern-age strategies that address some of these physiological barriers. The modern age designs include the 3D printed devices and formulations. The superiority of 3D dosage forms over conventional cargos is summarized with a focus on long-acting designs. The innovations in Pharmaceutical organizations (Lyndra, Assertio and Intec) that have taken giant steps towards commercialization of long-acting vehicles are discussed. The recent advancements made in the arena of oral peptide delivery are also highlighted. The review represents a comprehensive journey from Nano-formulations to micro-fabricated oral implants aiming at specific patient-centric designs.

Phenomenology of the Initial Burst Release of Drugs from PLGA Microparticles

Poly(lactic-co-glycolic acid) (PLGA) is the most prevalent polymer drug delivery vehicle in use today. There are about 20 commercialized drug products in which PLGA is used as an excipient. In more than half of these formulations, PLGA is used in the form of microparticles (with sizes in the range between 60 nm and 100 μm). The primary role of PLGA is to control the kinetics of drug release toward achieving sustained release of the drug. Unfortunately, most drug-loaded PLGA microparticles exhibit a common drawback: an initial uncontrolled burst of the drug. After 30 years of utilization of PLGA in controlled drug delivery systems, this initial burst drug release still remains an unresolved challenge. In this Review, we present a summary of the proposed mechanisms responsible for this phenomenon and the known factors affecting the burst release process. Also, we discuss examples of recent efforts made to reduce the initial burst release of the drug from PLGA particles.

Injectable Lipid-Based Depot Formulations: Where Do We Stand?

The remarkable number of new molecular entities approved per year as parenteral drugs, such as biologics and complex active pharmaceutical ingredients, calls for innovative and tunable drug delivery systems. Besides making these classes of drugs available in the body, injectable depot formulations offer the unique advantage in the parenteral world of reducing the number of required injections, thus increasing effectiveness as well as patient compliance. To date, a plethora of excipients has been proposed to formulate depot systems, and among those, lipids stand out due to their unique biocompatibility properties and safety profile. Looking at the several long-acting drug delivery systems based on lipids designed so far, a legitimate question may arise: How far away are we from an ideal depot formulation? Here, we review sustained release lipid-based platforms developed in the last 5 years, namely oil-based solutions, liposomal systems, in situ forming systems, solid particles, and implants, and we critically discuss the requirements for an ideal depot formulation with respect to the used excipients, biocompatibility, and the challenges presented by the manufacturing process. Finally, we delve into lights and shadows originating from the current setups of in vitro release assays developed with the aim of assessing the translational potential of depot injectables.

Factors defining the stability of poly(lactide-co-glycolide) spheres for the sustained release of a cysteine protease inhibitor

Colloidal stability and the regularity of the release kinetics benefit from the high circularity and the narrow size dispersion of polymeric particles as drug delivery carriers. A method for obtaining such particles composed of poly(lactide-co-glycolide) (PLGA), averaging at 1.0 ± 0.3 µm in size, is reported here, along with the analysis of the effects of different synthesis parameters on their morphological characteristics. As in agreement with the classical nucleation theory, the particle size and the degree of cohesion were inversely proportional to supersaturation. Consequently, the optimal conditions for the precipitation of small and narrowly dispersed particles involved an abrupt elevation of supersaturation. Owing to the high colloidal stability of the particles, centrifugation exhibited a counterintuitive effect on them, refining their morphological features and promoting their individuation. Polyvinyl alcohol (PVA) was used as a steric repulsion additive and its effect on the stability of PLGA spheres was concentration-dependent, with the particles aggregating, partially coalescing and losing their distinct features both with no PVA in the system and at PVA concentrations higher than the optimal. At its narrowest, the particle size distribution was bimodal, exhibiting the average circularity of 0.997 ± 0.003 and the average roundness of 0.913 ± 0.054. PLGA spheres were loaded with an inhibitor of EhCP4, a cysteine protease from E. histolytica, a parasite causing amoebic dysentery in the tropical and developing world. The burst release of the drug at early time points was followed by a zero-order release period, yielding a biphasic profile that can be of benefit in the delivery of anti-infective agents. The release profile fitted poorly with the Hixson-Crowell kinetic model and excellently with the Higuchi and the Korsmeyer-Peppas ones, indicating that the release is conditioned by diffusion rather than by the degradation of the polymer. The release and the erosion proceeded independently from one another, suggesting that the pore formation, water penetration and swelling are the primary driving forces for the release of the drug.