Constant Release Profile Research Articles

Core-shell electrospun polycaprolactone nanofibers, loaded with rifampicin and coated with silver nanoparticles, for tissue engineering applications

In the field of tissue engineering, the use of core-shell fibers represents an advantageous approach to protect and finely tune the release of bioactive compounds with the aim to regulate their efficacy. In this work, core-shell electrospun polycaprolactone nanofiber-based membranes, loaded with rifampicin and coated with silver nanoparticles, were developed and characterized. The membranes are composed by randomly oriented nanofibers with a homogeneous diameter, as demonstrated by scanning electron microscopy (SEM). An air-plasma treatment was applied to increase the hydrophilicity of the membranes as confirmed by contact angle measurements. The rifampicin release from untreated and air-plasma treated membranes, evaluated by UV spectrophotometry, displayed a similar and constant over-time release profile, demonstrating that the air-plasma treatment does not degrade the rifampicin, loaded in the core region of the nanofibers. The presence and the distribution of silver nanoparticles on the nanofiber surface were investigated by SEM and Energy Dispersive Spectroscopy. Moreover, SEM imaging demonstrated that the produced membranes possess a good stability over time, in terms of structure maintenance. The developed membranes showed a good biocompatibility towards murine fibroblasts, human osteosarcoma cells and urotheliocytes, reveling the absence of cytotoxic effects. Moreover, doble-functionalized membranes inhibit the growth of E. coli and S. aureus. Thanks to the possibilities offered by the coaxial electrospinning, the membranes here proposed are promising for several tissue engineering applications.

Real-Time Monitoring Platform for Ocular Drug Delivery.

Real-time measurement is important in modern dissolution testing to aid in parallel drug characterisation and quality control (QC). The development of a real-time monitoring platform (microfluidic system, a novel eye movement platform with temperature sensors and accelerometers and a concentration probe setup) in conjunction with an in vitro model of the human eye (PK-Eye™) is reported. The importance of surface membrane permeability when modelling the PK-Eye™ was determined with a "pursing model" (a simplified setup of the hyaloid membrane). Parallel microfluidic control of PK-Eye™ models from a single source of pressure was performed with a ratio of 1:6 (pressure source:models) demonstrating scalability and reproducibility of pressure-flow data. Pore size and exposed surface area helped obtain a physiological range of intraocular pressure (IOP) within the models, demonstrating the need to reproduce in vitro dimensions as closely as possible to the real eye. Variation of aqueous humour flow rate throughout the day was demonstrated with a developed circadian rhythm program. Capabilities of different eye movements were programmed and achieved with an in-house eye movement platform. A concentration probe recorded the real-time concentration monitoring of injected albumin-conjugated Alexa Fluor 488 (Alexa albumin), which displayed constant release profiles. These results demonstrate the possibility of real-time monitoring of a pharmaceutical model for preclinical testing of ocular formulations.

Comparative Pharmacokinetics and Local Tolerance of Tenofovir Alafenamide (TAF) From Subcutaneous Implant in Rabbits, Dogs, and Macaques.

The administration of antiretrovirals (ARVs) for HIV pre-exposure prophylaxis (PrEP) is highly efficacious and may benefit from new long-acting (LA) drug delivery approaches. This paper describes a subcutaneous, reservoir-style implant for the LA delivery of tenofovir alafenamide (TAF) and documents the preclinical assessment of implant safety and pharmacokinetics (PK) in New Zealand White (NZW) rabbits (3 groups of n = 5), beagle dogs (2 groups of n = 6), and rhesus macaques (2 groups of n = 3). Placebo implants were placed in rabbits (n = 10) and dogs (n = 12). Implant parameters, including selection of the TAF form, choice of excipient, and PCL formulation were tuned to achieve targeted concentrations of the active anabolite of TAF, tenofovir diphosphate (TFV-DP), within peripheral blood mononuclear cells (PBMCs) and mucosal tissues relevant to HIV transmission. Sustained concentrations of TFV-DP in PBMCs over 100 fmol/106 cells were achieved in all animal species indicating that the implants effectively delivered TAF for 3–6 months. Unlike placebo implants without TAF, all active implants resulted in local adverse events (AEs) proximal to the implant ranging in severity from mild to moderate and included dermal inflammation and necrosis across all species. Despite these AEs, the implant performed as designed and achieved a constant drug release profile, supporting the continued development of this drug delivery platform.

Successful Dendrimer and Liposome-Based Strategies to Solubilize an Antiproliferative Pyrazole Otherwise Not Clinically Applicable.

Water-soluble formulations of the pyrazole derivative 3-(4-chlorophenyl)-5-(4-nitrophenylamino)-1H-pyrazole-4-carbonitrile (CR232), which were proven to have in vitro antiproliferative effects on different cancer cell lines, were prepared by two diverse nanotechnological approaches. Importantly, without using harmful organic solvents or additives potentially toxic to humans, CR232 was firstly entrapped in a biodegradable fifth-generation dendrimer containing lysine (G5K). CR232-G5K nanoparticles (CR232-G5K NPs) were obtained with high loading (DL%) and encapsulation efficiency (EE%), which showed a complex but quantitative release profile governed by Weibull kinetics. Secondly, starting from hydrogenated soy phosphatidylcholine and cholesterol, we prepared biocompatible CR232-loaded liposomes (CR232-SUVs), which displayed DL% and EE% values increasing with the increase in the lipids/CR232 ratio initially adopted and showed a constant prolonged release profile ruled by zero-order kinetics. When relevant, attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR) and nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM) and dynamic light scattering (DLS) experiments, as well as potentiometric titrations completed the characterization of the prepared NPs. CR232-G5K NPs were 2311-fold more water-soluble than the pristine CR232, and the CR232-SUVs with the highest DL% were 1764-fold more soluble than the untreated CR232, thus establishing the success of both our strategies.

Customizable drug tablets with constant release profiles via 3D printing technology

Medicine should ideally be personalized as each individual has his/her own unique biological, physical, and medical dispositions. Medicine can be personalized by customizing drug tablets with the specific drug dosages, release durations, and combinations of multiple drugs. This study presents a method for fabricating drug tablets with customizable dosages, durations, and combinations of multiple drugs by using the 3D printing technology. The method focuses on fabricating customizable drug tablets with a very simple structure for delivering the constant release profile due to its importance in treatment (i.e., the drug may produce side effects if too much is released andmay not have therapeutic value is too little is released). The method is simple: it involves first printing a template using the 3D printer and fabricating the drug tablet via the template. The tablets are customized by varying the amount of excipient used, the height of the tablet, and the numberand amount of drugs used. Three different common drugs (i.e., paracetamol, phenylephrine HCl and diphenhydramine HCl) and FDA-approved excipients are studied. The simplicity of the structure of the tablet and method via templating allows the fabrication of these fully customizable drug tablets to be easily performed, low-cost, efficient, and safe for consumption. These features enable the customizable tablets to be made widely accessible to the public; hence, the concept of personalized medicine can be realized.

Synthesis and application of magnetic@layered double hydroxide as an anti-inflammatory drugs nanocarrier

BackgroundMagnetic nanocomposites with a core–shell nanostructure have huge applications in different sciences especially in the release of the drugs, because of their exclusive physical and chemical properties. In this research, magnetic@layered double hydroxide multicore@shell nanostructure was synthesized by the facile experiment and is used as novel drug nanocarrier.MethodsMagnetic nanospheres were synthesized by a facile one-step solvothermal route, and then, layered double hydroxide nanoflakes were prepared on the magnetic nanospheres by coprecipitation experiment. The synthesized nanostructures were characterized by FTIR, XRD, SEM, VSM, and TEM, respectively. After intercalation with Ibuprofen and Diclofenac as anti-inflammatory drugs and using exchange anion experiment, the basal spacing of synthesized layered double hydroxides was compared with brucite nanosheets from 0.48 nm to 2.62 nm and 2.22 nm, respectively.ResultsThe results indicated that Ibuprofen and Diclofenac were successfully intercalated into the interlay space of LDHs via bridging bidentate interaction. In addition, in-vitro drug release experiments in pH 7.4, phosphate-buffered saline (PBS) showed constant release profiles with Ibuprofen and Diclofenac as model drugs with different lipophilicity, water solubility, size, and steric effect.ConclusionThe Fe3O4@LDH-ibuprofen and Fe3O4@LDH-diclofenac had the advantage of the strong interaction between the carboxyl groups with higher trivalent cations by bridging bidentate, clarity, and high thermal stability. It is confirmed that Fe3O4@LDH multicore-shell nanostructure may have potential application for constant drug delivery.

Intercalation and release of an anti-inflammatory drug into designed three-dimensionally layered double hydroxide nanostructure via calcination–reconstruction route

Synthesis and application of layered nanomaterials are known as emerging field in nanotechnology. Inorganic layered nanomaterials with nanometer scale, high aspect ratios, and large-surface area generate various scientific and technological interests in several potential areas of application such as separation technology, medical sciences, chromatography drug delivery, and catalysis. In this research, naproxen was opted as a unique model of the drug to intercalate into three-dimensional layered double hydroxide (LDH) nanostructures by calcination–reconstruction method. The designed-naproxen nanostructures were synthesized and used as novel drug nanocarriers. The synthesized nanomaterial characteristics were confirmed by FTIR, XRD, and SEM. The results of antibacterial activity indicated that homemade nanostructure can inhibit bacterial growth. Furthermore, MTT assay analysis showed that synthesized-nanostructure in physiological concentration has not cytotoxicity on C2C12 myoblast cells in vitro. Subsequent to intercalation with naproxen according to calcination–reconstruction method, the basal spacing of LDH increased to 2.62 nm from primary 0.77 nm in diameter, which confirms successful intercalation of naproxen into inserted layer of LDH by bridging interaction. Also, in-vitro drug release tests in PBS (pH 7.4) showed constant release profile for naproxen. Consequently, due to the facile and low-cost fabrication of three-dimensional LDH nanostructure, it can be considered as a potential alternative for traditional and high cost drug delivery.

3D Printed Polyvinyl Alcohol Tablets with Multiple Release Profiles

The aim of this study was to explore the feasibility of using different 3D printed internal geometries as tablet formulations to obtain controlled release profiles. In order to obtain controllable release profiles, three types of tablet models (Cylinder, Horn and Reversed Horn) with controlled structures were designed. The cylinder model shows a constant release profile and can keep the drug concentration within a certain range. The horn model exhibits an increasing release profile, which is suitable for the patients who have the drug resistance in the course of medication. The reversed horn model has a decreasing release profile that would be applied to hypertension cure. Furthermore, three types of tablets were fabricated successfully by a fused deposition modeling three-dimensional (3D) printer and injected with paracetamol (APAP) -containing gels. The results of in vitro drug release demonstrate that tablets with three kinds of structures can produce constant, gradually increasing, and gradually decreasing release profiles, respectively. The release attributes can be controlled by using different 3D printed geometries as tablet formulations. More importantly, there are no residues after dissolution. The method of preparing customized tablets with distinguished release profiles presented in this study has the promising potential in the fabrication of patient-tailored medicines.

Injectable drug depot engineered to release multiple ophthalmic therapeutic agents with precise time profiles for postoperative treatment following ocular surgery

A multi-drug delivery platform is developed to address current shortcomings of post-operative ocular drug delivery. The sustained biodegradable drug release system is composed of biodegradable polymeric microparticles (MPs) incorporated into a bulk biodegradable hydrogel made from triblock copolymers with poly(ethylene glycol) (PEG) center blocks and hydrophobic biodegradable polyester blocks such as poly(lactide-co-glycolide) (PLGA), Poly(lactic acid) (PLA), or Poly(lactide-co-caprolactone) (PLCL) blocks. This system is engineered to flow as a liquid solution at room temperature for facile injection into the eye and then quickly gel as it warms to physiological body temperatures (approximately 37 °C). The hydrogel acts as an ocular depot that can release three different drug molecules at programmed rates and times to provide optimal release of each species. In this manuscript, the hydrogel is configured to release a broad-spectrum antibiotic, a potent corticosteroid, and an ocular hypotensive, three ophthalmic therapeutic agents that are essential for post-operative management after ocular surgery, each drug released at its own timescale. The delivery platform is designed to mimic current topical application of postoperative ocular formulations, releasing the antibiotic for up to a week, and the corticosteroid and the ocular hypotensive agents for at least a month. Hydrophobic blocks, such as PLCL, were utilized to prolong the release duration of the biomolecules. This system also enables customization by being able to vary the initial drug loading to linearly tune the drug dose released, while maintaining a constant drug release profile over time. This minimally invasive biodegradable multi-drug delivery system is capable of replacing a complex ocular treatment regimen with a simple injection. Such a depot system has the potential to increase patient medication compliance and reduce both the immediate and late term complications following ophthalmic surgery. Statement of SignificanceAfter ocular surgery, patients routinely receive multiple medications including antibiotics, steroids and ocular hypotensives to ensure optimal surgical outcomes. The current standard of care for postoperative treatment after ocular surgery involves using eye drops daily, which has limited effectiveness mainly due to poor patient adherence. To improve patient experience and outcomes, this article presents the first thermoresponsive hydrogel able to release multiple drug molecules for the application of post-operative treatment following ocular surgery. By varying the parameters such as hydrogel type and polymer hydrophobicity, the drug release profile, duration and dosage can finely be tuned. The approach presented in this article can readily be applied to other applications by simply changing the drug loaded in the drug delivery system.

Curcumin-Loaded Nanoparticles Protect Against Rhabdomyolysis-Induced Acute Kidney Injury

Background/Aims: Rhabdomyolysis (RM) is a potentially life-threatening condition that results from the breakdown of muscle and consequent release of toxic compounds into circulation. The most common and severe complication of RM is acute kidney injury (AKI). This study aimed to evaluate the efficacy and mechanisms of action of curcumin-loaded nanoparticles (Cur-NP) for treatment of RM-induced AKI. Methods: Curcumin-NP was synthesized using the nanocarrier distearoylphosphatidylethanolamine-polyethylene glycol (DSPE-PEG) to achieve a prolonged and constant drug release profile compared with the curcumin-free group. The anti-AKI effects of Curcumin-NP were examined both in vitro (myoglobin-treated renal tubular epithelial HK-2 cells) and in vivo (glycerol-induced AKI model). Results: Our results indicated that Curcumin-NP reversed oxidative stress, growth inhibition and cell apoptosis accompanied with down-regulation of apoptotic markers Caspase-3 and GRP-78 in vitro. In vivo studies revealed enhanced AKI treatment efficacy with Curcumin-NP as characterized by reduced serum creatine phosphokinase (CPK), creatinine (Cr) and urea and less severe histological damage in renal tubules. In addition, kidney tissues from Curcumin-NP-treated AKI rats exhibited reduced oxidative stress, apoptosis, and cleaved Capase-3 and GRP-78 expression. Conclusion: Our results suggest that nanoparticle-loaded curcumin enhances treatment efficacy for RM-induced AKI both in vitro and in vivo.

Solid lipid nanoparticles as promising tool for intraocular tobramycin delivery: Pharmacokinetic studies on rabbits

Eye drops are widely accepted as formulations for targeting the anterior segment notwithstanding their limitations in terms of bioavailability. The unique structure of the eye requires specially-designed formulations able to favor the pharmacokinetic profile of administered drugs, mainly minimizing the influence of ocular barriers. Nanotechnology-based delivery systems lead to significant technological and therapeutical advantages in ophthalmic therapy.The aim of the present study was to determine whether tobramycin as ion-pair incorporated in mucoadhesive Solid Lipid Nanoparticles (SLN) reaches the inner parts of the eye favoring drug activity.After technological characterization of the tobramycin entrapped SLN formulation (Tobra-SLN), a pharmacokinetic study in rabbits after topical instillation and intravenous administration of the formulation has been carried out. In addition, the intracellular activity of Tobra-SLN formulation against phagocytosed Pseudomonas aeruginosa was investigated.The SLN were spherical in shape, and showed a hydrodynamic diameter of about 80nm, a negative zeta potential (−25.7mV) with a polydispersity index of 0.15, representative of a colloidal dispersion with high quality, characterized by an unimodal relatively narrow size distribution. As demonstrated by FTIR and DSC, tobramycin ion-pair could be concentrated into lipid inner core of SLN, without interaction with the stearic acid, thus promoting a slow and constant drug release profile in the dissolution medium.Surprisingly, the drug concentration was significantly higher in all ocular tissues after ocular and intravenous administration of Tobra-SLN formulation with respect to reference formulations and only Tobra-SLN allowed the penetration of drug into retina. Furthermore, the use of Tobra-SLN resulted in both higher intraphagocytic antibiotic concentrations in polymorphonuclear granulocytes and greater bactericidal activity against intracellular Pseudomonas aeruginosa, probably due to the ability of Tobra-SLN to penetrate either into phagocytic cells, or alternatively to cross bacterial barrier.The present study broadens the knowledge on the use of SLN as carriers for ocular drug delivery to the posterior chamber and might open new avenues for treatment of ocular infections, representing a strategy to overcome the microbial resistance.

Design, preparation and characterization of novel poly-lactic-co-glycolic acid‑hyaluronic acid implants containing triptorelin acetate

Hormones and their derivatives are widely used to treat different types of diseases such as prostate cancer which is treated by agonists of gonadotropin‑releasing hormone. Triptoreline salts are the first therapeutics of this group launched into the market in the form of microparticles (microspheres). Implants, as one of attractive injectable dosage forms, have many advantages over multi‑particulate systems. Some of these advantages are dose adjustability, drug absorption improvement, constant release profile, etc. In this research, a new composite of poly‑lactic‑co‑glycolic acid and hyaluronic acid was designed and prepared in the form of implants containing triptorelin acetate for administration as an injection under the skin (subcutaneously) in arm or thigh area. The manufactured implants characterized by Fourier transform infrared spectroscopy, thermas gravimetric analysis, X‑ray diffraction and scanning electron microscopy to assess different aspects of structure and morphology. The drug release profile was assessed by high performance liquid chromatography. These characterizations confirmed that the newly designed drug delivery has a good stability during manufacturing process. The release pattern of the implant was also studied and revealed that the release of the model drug follows a zero‑order and erosion mechanism. The compatibility between the components of the newly designed implants and the release profile of the delivery system make it a promising device for drug delivery.

Development of an intravitreal peptide (BQ123) sustained release system based on poly(2-hydroxyoctanoic acid) aiming at a retinal vasodilator response.

Development of a novel formulation for intravitreal administration, in which the endothelinA receptor antagonist BQ123 is incorporated in a biodegradable and injectable polymer drug delivery system, poly(2-hydroxyoctanoic acid), aiming at a prolonged retinal vasodilator response. BQ123 was incorporated in poly(2-hydroxyoctanoic acid), leading to an easily injectable, homogenous mixture. In vitro release profiles were obtained in porcine vitreous humor (n=6). The ex vivo biocompatibility was studied by placing the formulation in contact with porcine retinal tissues and performing histology. In a pilot in vivo study, the change in retinal vessel diameter of mini pigs (n=2) was followed over 3 h after an intravitreal injection of the formulation, as well as the release of BQ123 from the polymer system for approximately 7 days (n=6). In vitro, a constant release profile was obtained, releasing approximately 91% of BQ123 within 7 days. Histology on the porcine retinal tissues showed good ex vivo biocompatibility. In vivo, a vasodilative response was observed, with a retinal vessel diameter increase from 14% after 15 min, for approximately 39% after 3 h. At t=3 h, the BQ123 concentration in the vitreous humor was 0.7±0.2 μg/mL, followed by 1.5±1.0 and 1.1±0.8 μg/mL after 3 and 7 days, respectively. 39.9%±6.0% of BQ123 was still present in the polymer depot at t=7 days. The results show that an intravitreal injection of this drug delivery system leads to a prolonged vasodilative response and a BQ123 release over 7 days, suggesting its therapeutic potential in the management of retinal ischemic conditions.

Design and in vitro assessment of L-lactic acid-based copolymers as prodrug and carrier for intravitreal sustained L-lactate release to reverse retinal arteriolar occlusions

Ophthalmic conditions in which the retinal vasculature is obstructed generally lead to vision loss. Administration of the vasodilator L-lactate might offer a treatment strategy by restoring the blood flow, but unfortunately its effect after single intravitreal injection is short-lived. This study describes a concept in which the sustained release of L-lactic acid from a biodegradable copolymer system is investigated. The 50:50 (n/n) copolymer system, composed of L-lactic acid and L,D-2-hydroxyoctanoic acid, is a viscous injectable that will form an intravitreal drug depot. Hydrolysis of the copolymer will automatically lead to the release of L-lactic acid, which will convert to L-lactate at physiological pH, thereby providing a carrier and pro-drug in one. In vitro and ex vivo release studies demonstrate an L-lactic acid release over several weeks. Biocompatibility of the co-polymer and its degradation products is shown on a human retinal pigment epithelial cell line and on ex vivo retinal tissues. A low molecular weight copolymer (1200g/mol) with low polydispersity has promising properties with a constant release profile, good biocompatibility and injectability.

Biodegradable three-dimension micro-device delivering 5-fluorouracil in tumor bearing mice

A novel three-dimension micro-device was formulated to control delivery of 5-fluorouracil (5-FU) for the treatment of solid tumors. The poly-(lactic-co-glycolic) acid (PLGA), which is both biocompatible and biodegradable, was used as carrier material. The characteristics of drug release in vitro and in vivo and the performance of the micro-device after implantation in tumor bearing mice were evaluated. A constant release profile from in vitro test was obtained for a period of 7 days, and it correlated well with the in vivo release profile. In the distribution experiment of 5-FU micro-device, it was demonstrated that 5-FU remained in the tumor tissues for more than 7 days after implantation. Likewise, we found that the 5-FU concentration in tumor correlated well with the in vivo release. Tumors treated with 5-FU loaded micro-device of three different dosages showed significant tumor reduction (P < 0.05) compared with empty control micro-device 7 days after administration. Moreover, the implantation treatment showed enhanced efficacy compared with the intraperitoneal administration with the same dosage. These results suggested that the three-dimensional micro-device may provide a promising local and controlled release drug delivery system, which may enable delivery of multiple drugs for post-surgical chemotherapy against solid tumor.

A Timely Review of State-of-the-Art Chronopharmaceuticals Synchronized with Biological Rhythms

Extensive research into circadian rhythms and their influence on biological systems has given rise to the science of chronobiology and subsequently chronotherapy, the science of delivering drugs in synchrony with biological rhythms. The field of chronotherapeutics paves the way for advances and complexities in current drug delivery technology. The ultimate goal of current chronopharmaceutical research strives to design ideal chronotherapeutic drug delivery systems that respond to such therapeutic needs. Considering the fact that physiological events such as heart rate, blood pressure, plasma concentration of hormones, plasma proteins and enzymes display constancy over time, drug delivery systems with constant release profiles have thus been favored. However, due to circadian rhythms, the conventional paradigm of constant drug delivery may not be what is needed. Instead, precisely timed drug delivery systems are required in order to correlate drug delivery with circadian rhythms to provide maximum therapeutic efficacy for chronotherapeutic diseases when most needed. The aim of this review paper is to outline the concepts in designing chronopharmaceuticals from a clinical viewpoint of major chronotherapeutic diseases such as asthma, allergic rhinitis, cardiovascular disorders, rheumatoid arthritis and cancer as well as relatively minor niche areas of interest such as in glaucoma, diabetes, immunity, pain, gastric ulcers, epilepsy and even HIV/AIDS that would require chronotherapy. In addition this review paper attempts to concisely assimilate and explicate the role of circadian rhythms in these various disease states and provide a focused overview of the current state-of-the-art in designing strategies for chronopharmaceutical formulations employed for treating chronotherapeutic diseases.

Nucleic Acid Therapeutic Carriers with On-Demand Triggered Release

Biohybrid platforms such as synthetic polymer networks engineered from artificial and natural materials hold immense potential as drug and gene delivery vehicles. Here, we report the synthesis and characterization of novel polymer networks that release oligonucleotide sequences via enzymatic and physical triggers. Chemical monomers and acrylated oligonucleotides were copolymerized into networks, and phosphoimaging revealed that 70% of the oligonucleotides were incorporated into the networks. We observed that the immobilized oligonucleotides were readily cleaved when the networks were incubated with the type II restriction enzyme BamHI. The diffusion of the cleaved fragments through the macromolecular chains resulted in relatively constant release profiles very close to zero-order. To our knowledge, this is the first study which harnesses the sequence-specificity of restriction endonucleases as triggering agents for the cleavage and release of oligonucleotide sequences from a synthetic polymer network. The polymer networks exhibited an oligonucleotide diffusion coefficient of 5.6 x 10(-8) cm(2)/s and a diffusional exponent of 0.92. Sigmoidal temperature responsive characteristics of the networks matched the theoretical melting temperature of the oligonucleotides and indicated a cooperative melting transition of the oligonucleotides. The networks were also triggered to release a RNA-cleaving deoxyribozyme, which degraded a HIV-1 mRNA transcript in vitro. To tailor release profiles of the oligonucleotides, we controlled the structure of the macromolecular architecture of the networks by varying their cross-linking content. When incubated with DNase I, networks of cross-linking content 0.15%, 0.22%, and 0.45% exhibited oligonucleotide diffusion coefficients of 1.67 x 10(-8), 7.65 x 10(-9), and 2.7 x 10(-9) cm(2)/s, and diffusional exponents of 0.55, 0.8, and 0.8, respectively. The modular nature of our platform promises to open new avenues for the creation and optimization of a rich toolbox of novel drug and gene delivery platforms. We anticipate further inquiry into nucleic acid based programmable on-demand switches and modulatory devices of exquisite sensitivity and control.

Alginate Based Microparticle Drug Delivery Systems for the Treatment of Eye Cancer

AbstractAlginate based microparticle drug delivery systems were prepared for the sustained release of antitumor drugs. Two drugs, cyclophosphane and 5-fluorouracil, were encapsulated into the microparticles. The drug loaded microparticles were fabricated using a very convenient method under very mild conditions by the gelation of alginate with calcium cation. Modified microparticles were obtained by syringed dropwise a solution of drugs in sodium alginate into chitosan solution in calcium chloride. The effect of polymers concentration and the drug loading (1.0, 5.0 and 10%) on the release profile of drugs were investigated. The amount of drug release was much higher initially (approximately 25%), followed by a constant slow release profile. All the release data show the typical pattern for a matrix controlled mechanism. The cumulative amount of drug released from alginate gels was linearly related to the square root of the time and the release rate decreased this time. The process is controlled by the diffusion of antitumor drugs through the chitosan coating. Scanning electron microscopy (SEM) and particle size analysis revealed differences between the formulations as to their appearance and size distribution. The experiments for anticancer action of alginate microparticles were determined at 120 inbreeded white rats (females, weight 120-125 g, age 2-3 month) infected by malignant Rhabdomyoma strain at the dose of 10 000 cells. Medical-biological tests show that the duration of anticancer activity for the drug-containing alginate microparticles increases at 5-8 times in comparison of free drugs. Such systems may have potential for controlled delivery of antitumor drugs for the treatment of eye cancer

Effect of Formulation on Methylphenidate Release Patterns

Attention-deficit hyperactivity disorder (ADHD) is the most common psychiatric disorder in children. Currently, the most widely prescribed therapy for ADHD is methylphenidate. Several formulations of methylphenidate have been developed that modify the delivery of the drug into the body. These include immediate-release (IR) tablets and modified-release preparations including sustained-release tablets, controlled-delivery capsules and tablets, and transdermal delivery systems. The IR tablet is taken two or three times daily and has been demonstrated to show efficacy through its rapid onset of action. The modified-release formulations deliver methylphenidate at a controlled rate and are administered once daily; they were developed to mimic the efficacy of the IR tablet by controlling drug release. The latest formulation development efforts have been directed towards combining the rapid release and onset of action of an IR component with an extended-release component that would maintain drug levels and allow for once-daily administration. The rationale for the development of various delivery systems of methylphenidate stems from the need for drug coverage for at least 8 hours for ADHD patients. This would maintain efficacy over the entire school day and would eliminate the need for repeated administrations while the patient was at school. Early formulation development targeted a constant-release profile or an apparent zero-order input with the intention of maintaining plasma drug levels at a constant level for the required time period. However, it was demonstrated that the constant delivery of methylphenidate did not provide equivalent efficacy to the repeated administration of the IR product over the school day and resulted in tolerance to the effects of the drug. This suggested that sustained-release formulations that maintained constant drug levels over the treatment period would not result in the optimal therapeutic condition. In contrast, a drug delivery profile that maintained a drug release pattern with increase-release kinetics would be able to overcome the tolerance that was observed with the constant delivery formulations. Therefore, the formulation development for modified-release once-daily administration products of methylphenidate has been targeted to mimic the repeated administrations of IR methylphenidate.

“Programmed Polymeric Devices” for Pulsed Drug Delivery

Pharmaceutical research strives to design drug delivery systems that respond to therapeutic needs. Considering the facts that physiologic parameters (e.g., heart rate, blood pressure, and plasma concentration of hormones, plasma proteins, and enzymes) display constancy over time, drug delivery systems with a constant release profile have been designed. However, because of circadian rhythms in physiologic parameters and pathologic conditions (e.g., asthma, angina pectoris), the conventional paradigm concerning drug concentrations "the flatter the better" may not be what the organism may need. Instead, to correlate with our biological needs, "precisely timed drug delivery," which could be accomplished with "programmable dosage forms," is required. Precisely timed drug delivery may maximize therapeutic efficacy, may minimize dose frequency, and may reduce toxicity by avoiding side effects and drug tolerance. This paper outlines the concepts that have been proposed to release drugs in a pulsed manner from pharmaceutical devices.