Role of polyanhydrides as localized drug carriers

Dual Chemotherapeutic Loading in Oxalate Transferrin-Conjugated Polymersomes Incorporated into Chitosan Hydrogels for Site-Specific Targeting of Melanoma Cells

In this work, we developed a smart drug delivery system composed of poly (ethylene glycol)-block-poly (ε-caprolactone) (PEG-PCL)-based polymersomes (Ps) loaded with doxorubicin (DOX) and vemurafenib (VEM). To enhance targeted delivery to malignant melanoma cells, these drug-loaded nanovesicles were conjugated to the oxalate transferrin variant (oxalate Tf) and incorporated into three-dimensional chitosan hydrogels. This innovative approach represents the first application of oxalate Tf for the precision delivery of drug-loaded polymersomes within a semi-solid dosage form based on chitosan hydrogels. These resulting semi-solids exhibited a sustained release profile for both encapsulated drugs. To evaluate their potency, we compared the cytotoxicity of native Tf-Ps with oxalate Tf-Ps. Notably, the oxalate Tf-Ps demonstrated a 3-fold decrease in cell viability against melanoma cells compared to normal cells and were 1.6-fold more potent than native Tf-Ps, indicating the greater potency of this nanoformulation. These findings suggest that dual-drug delivery using an oxalate-Tf-targeting ligand significantly enhances the drug delivery efficiency of Tf-conjugated nanovesicles and offers a promising strategy to overcome the challenge of multidrug resistance in melanoma therapy.

Biodegradable Conducting Polymer-Based Composites for Biomedical Applications-A Review

In recent years, researchers have increasingly directed their focus toward the biomedical field, driven by the goal of engineering polymer systems that possess a unique combination of both electrical conductivity and biodegradability. This convergence of properties holds significant promise, as it addresses a fundamental requirement for biomedical applications: compatibility with biological environments. These polymer systems are viewed as auspicious biomaterials, precisely because they meet this critical criterion. Beyond their biodegradability, these materials offer a range of advantageous characteristics. Their exceptional processability enables facile fabrication into various forms, and their chemical stability ensures reliability in diverse physiological conditions. Moreover, their low production costs make them economically viable options for large-scale applications. Notably, their intrinsic electrical conductivity further distinguishes them, opening up possibilities for applications that demand such functionality. As the focus of this review, a survey into the use of biodegradable conducting polymers in tissue engineering, biomedical implants, and antibacterial applications is conducted.

Characteristics of Microparticles Based on Resorbable Polyhydroxyalkanoates Loaded with Antibacterial and Cytostatic Drugs

The development of controlled drug delivery systems, in the form of microparticles, is an important area of experimental pharmacology. The success of the design and the quality of the obtained microparticles are determined by the method of manufacture and the properties of the material used as a carrier. The goal is to obtain and characterize microparticles depending on their method of preparation, the chemical composition of the polymer and the load of the drugs. To obtain microparticles, four types of degradable PHAs, differing in their chemical compositions, degrees of crystallinity, molecular weights and temperature characteristics, were used (poly-3-hydroxybutyrate and copolymers 3-hydroxybutyric-co-3-hydroxyvaleric acid, 3-hydroxybutyric-co-4-hydroxybutyric acid, and 3-hydroxybutyric-co-3-hydroxyhexanoic acid). The characteristics of microparticles from PHAs were studied. Good-quality particles with an average particle diameter from 0.8 to 65.0 μm, having satisfactory ζ potential values (from -18 to -50 mV), were obtained. The drug loading content, encapsulation efficiency and in vitro release were characterized. Composite microparticles based on PHAs with additives of polyethylene glycol and polylactide-co-glycolide, and loaded with ceftriaxone and 5-fluorouracil, showed antibacterial and antitumor effects in E. coli and HeLa cultures. The results indicate the high potential of PHAs for the design of modern and efficient drug delivery systems.

Poly(sebacic acid) microparticles loaded with azithromycin as potential pulmonary drug delivery system: Physicochemical properties, antibacterial behavior, and cytocompatibility studies

Recurrent bacterial infections are a common cause of death for patients with cystic fibrosis and chronic obstructive pulmonary disease. Herein, we present the development of the degradable poly(sebacic acid) (PSA) microparticles loaded with different concentrations of azithromycin (AZ) as a potential powder formulation to deliver AZ locally to the lungs. We characterized microparticle size, morphology, zeta potential, encapsulation efficiency, interaction PSA with AZ and degradation profile in phosphate buffered saline (PBS). The antibacterial properties were evaluated using the Kirby-Bauer method against Staphylococcus aureus. Potential cytotoxicity was evaluated in BEAS-2B and A549 lung epithelial cells by the resazurin reduction assay and live/dead staining. The results show that microparticles are spherical and their size, being in the range of 1-5 μm, should be optimal for pulmonary delivery. The AZ encapsulation efficiency is nearly 100 % for all types of microparticles. The microparticles degradation rate is relatively fast - after 24 h their mass decreased by around 50 %. The antibacterial test showed that released AZ was able to successfully inhibit bacteria growth. The cytotoxicity test showed that the safe concentration of both unloaded and AZ-loaded microparticles was equal to 50 μg/ml. Thus, appropriate physicochemical properties, controlled degradation and drug release, cytocompatibility, and antibacterial behavior showed that our microparticles may be promising for the local treatment of lung infections.

Characterization of CPH:SA microparticle-based delivery of interleukin-1 alpha for cancer immunotherapy

Background

Interleukin-1 alpha (IL-1α) is a pro-inflammatory cytokine that can activate immune effector cells and trigger anti-tumor immune responses. However, dose-limiting toxicities including cytokine storm and hypotension has limited its use in the clinic as a cancer therapy. We propose that polymeric microparticle (MP)-based delivery of IL-1α will suppress the acute pro-inflammatory side effects by allowing for slow and controlled release of IL-1α systemically, while simultaneously triggering an anti-tumor immune response.

Methods

Polyanhydride copolymers composed of 1,6-bis-(p-carboxyphenoxy)-hexane:sebacic 20:80 (CPH:SA 20:80) was utilized to fabricate MPs. Recombinant IL-1α (rIL-1α) was encapsulated into CPH:SA 20:80 MPs (IL-1α-MPs) and the MPs were characterized by size, charge, loading efficiency, and in-vitro release and activity of IL-1α. IL-1α-MPs were injected intraperitonially into head and neck squamous cell carcinoma (HNSCC)-bearing C57Bl/6 mice and monitored for changes in weight, tumor growth, circulating cytokines/chemokines, hepatic and kidney enzymes, blood pressure, heart rate, and tumor-infiltrating immune cells.

Results

CPH:SA IL-1α-MPs demonstrated sustained release kinetics of IL-1α (100% protein released over 8-10 days) accompanied by minimal weight loss and systemic inflammation compared to rIL-1α-treated mice. Blood pressure measured by radiotelemetry in conscious mice demonstrates that rIL-1α-induced hypotension was prevented in IL-1α-MP-treated mice. Liver and kidney enzymes were within normal range for all control and cytokine-treated mice. Both rIL-1α and IL-1α-MP-treated mice showed similar delays in tumor growth and similar increases in tumor-infiltrating CD3+ T cells, macrophages, and dendritic cells.

Conclusions

CPH:SA-based IL-1α-MPs generated a slow and sustained systemic release of IL-1α resulting in reduced weight loss, systemic inflammation, and hypotension accompanied by an adequate anti-tumor immune response in HNSCC-tumor bearing mice. Therefore, MPs based on CPH:SA formulations may be promising as delivery vehicles for IL-1α to achieve safe, effective, and durable antitumor responses for HNSCC patients.

Preparation and Characterization of Polyanhydride Terminated with Oleic Acid Extracted from Olive Mills Waste

Valorizing the fatty content of agricultural waste in material synthesis is an interesting topic. This work focused on utilizing oleic acid from the solid waste of olive mills in Saudi Arabia to synthesize biodegradable polyanhydrides based on sebacic acid which terminated with different concentrations of fatty acid (10, 30, 50, and 70 wt%), then characterize the final polymer samples and study the effects of termination on polyanhydrides properties, such as molecular weight and degradation profile. The fatty content of the solid waste was extracted, purified, and analyzed prior to and after separating the saturated and unsaturated fractions by urea crystallization, then the microwave-assisted melt polycondensation technique was used in the synthesis of the final polymers. Molecular weights were determined by gel permeation chromatography (GPC), and the degradation profile of the prepared samples was examined by determining the weight loss percentage of the polymer mass and FT-IR scanning for the anhydride bond before and after sample degradation. Results showed a linear degradation profile for most samples with no significant change in the molecular weights due to termination.

Strategies to better treat glioblastoma: antiangiogenic agents and endothelial cell targeting agents

Glioblastoma multiforme (GBM) is the most prevalent and aggressive form of glioma, with poor prognosis and high mortality rates. As GBM is a highly vascularized cancer, antiangiogenic therapies to halt or minimize the rate of tumor growth are critical to improving treatment. In this review, antiangiogenic therapies, including small-molecule drugs, nucleic acids and proteins and peptides, are discussed. The authors further explore biomaterials that have been utilized to increase the bioavailability and bioactivity of antiangiogenic factors for better antitumor responses in GBM. Finally, the authors summarize the current status of biomaterial-based targeting moieties that target endothelial cells in GBM to more efficiently deliver therapeutics to these cells and avoid off-target cell or organ side effects.

Long lasting in-situ forming implant loaded with raloxifene HCl: An injectable delivery system for treatment of bone injuries

Bone injury is very serious in elder people or osteoporotic patients. In-situ forming implants (IFI) for bone rebuilding are usually poly-lactic-co-glycolic acid (PLGA)-based, which have a burst release effect. This study aimed to prepare novel liquid lipid-based PLGA-IFI loaded with raloxifene hydrochloride for prolonged non-surgical treatment of bone injuries by applying solvent-induced phase inversion technique. Labrasol® and Maisine® were added to the selected IFI forming long lasting lipid-based IFI (LLL-IFI). The formulations were characterized by analysing their in-vitro drug release, solidification time, injectability, rheological properties, and DSC in addition to their morphological properties. Results revealed that the LLL-IFI composed of 10%w/v PLGA with a lactide to glycolide ratio of 75:25 with ester terminal and 10% Maisine® possessed the most sustained drug release and lowest burst effect, as well as delayed pore formation compared to its counterpart lacking Maisine®. The selected LLL-IFI and PLGA-IFI formulations were tested for their capability to enhance bone regeneration in bone injuries induced in rats. Both formulations succeeded in healing the bones completely with the superiority of LLL-IFI in the formation of well-organized bone structures lacking fibrous tissues. The results suggest that LLL-IFI and PLGA-IFI are innovative approaches for treating critical and non-critical sized bone injuries.

Single Dose of a Polyanhydride Particle-Based Vaccine Generates Potent Antigen-Specific Antitumor Immune Responses

Many factors affect vaccine efficacy. One of the most salient is the frequency and intervals of vaccine administration. In this study, we assessed the vaccine administration modality for a recently reported polyanhydride-based vaccine formulation, shown to generate antitumor activity. Polyanhydride particles encapsulating ovalbumin (OVA) were prepared using a double-emulsion technique and subcutaneously delivered to mice either as a single-dose or as prime-boost vaccine regimens in which two different time intervals between prime and boost were assessed (7 or 21 days). This was followed by measurement of cellular and humoral immune responses, and subsequent challenge of the mice with a lethal dose of E.G7-OVA cells to evaluate tumor protection. Interestingly, a single dose of the polyanhydride particle-based formulation induced sustained OVA-specific cellular immune responses just as effectively as the prime-boost regimens. In addition, mice receiving single-dose vaccine had similar levels of protection against tumor challenge compared with mice administered prime-boosts. In contrast, measurements of OVA-specific IgG antibody titers indicated that a booster dose was required to stimulate strong humoral immune responses, since it was observed that mice administered a prime-boost vaccine had significantly higher OVA-specific IgG1 serum titers than mice administered a single dose. These findings indicate that the requirement for a booster dose using these particles appears unnecessary for the generation of effective cellular immunity.

Pentaerythritol-based lipid A bolsters the antitumor efficacy of a polyanhydride particle-based cancer vaccine

The primary objective of this study was to enhance the antitumor efficacy of a model cancer vaccine through co-delivery of pentaerythritol lipid A (PELA), an immunological adjuvant, and a model tumor antigen, ovalbumin (OVA), separately loaded into polyanhydride particles (PA). In vitro experiments showed that encapsulation of PELA into PA (PA-PELA) significantly enhanced its stimulatory capacity on dendritic cells as evidenced by increased levels of the cell surface costimulatory molecules, CD80/CD86. In vivo experiments showed that PA-PELA, in combination with OVA-loaded PA (PA-OVA), significantly expanded the OVA-specific CD8⁺ T lymphocyte population compared to PA-OVA alone. Furthermore, OVA-specific serum antibody titers of mice vaccinated with PA-OVA/PA-PELA displayed a significantly stronger shift toward a Th1-biased immune response compared to PA-OVA alone, as evidenced by the substantially higher IgG_2C:IgG₁ ratios achieved by the former. Analysis of E.G7-OVA tumor growth curves showed that mice vaccinated with PA-OVA/PA-PELA had the slowest average tumor growth rate.

Novel bioerodable eluting-spacers for radiotherapy applications with in situ dose painting

OBJECTIVE

To investigate feasibility of using bioerodable/bioerodible spacers (BES) over biodegradable spacers (BDS) loaded with gold nanoparticles for radiotherapy applications with in situ dose-painting, and to explore dosimetric impact on dose enhancement ratio of different radioisotopes.

METHODS

Analytical models proposed were based on experimentally reported erosion rate constant (k ₀ = 5. 5E-7 kgm^{- 2}s^{- 1} ) for bioerodible polymeric matrix. An in vivo determined diffusion coefficient (2.2E-8 cm²/s) of 10 nm gold nanoparticles (AuNP) of concentration 7 mg/g was used to estimate diffusion coefficient of other AuNP sizes (2, 5, 14 nm) using the Stoke-Einstein diffusion equation. The corresponding dose enhancement factors (DEF) were used to study dosimetric feasibility of employing AuNP-eluting BPS for radiotherapy applications.

RESULTS

The results showed AuNP release period from BES was significantly shorter (116 h) compared to BDS (more than a month) reported previously. The results also agree with reported Hopfenberg equation for a cylindrical matrix undergoing surface erosion. The DEF at tumour distance 5 mm for Cs-131 (DEF > 2.2) greater than that of I-125 (DEF > 2) and Pd-103 (DEF ≥ 2) could be achieved for AuNP sizes (2, 5, 10, and 14 nm) respectively.

CONCLUSION

Our findings suggested that BES could be used for short-lived radioisotopes like Pd-103 and Cs-131 in comparison to eluting BDS which is feasible for long-lived radioisotopes like I-125.

ADVANCES IN KNOWLEDGE

The study provides scientific basis for development of new generation eluting spacers viable for enhancing localized tumour dose. It concludes that BES gives higher DEF for Cs-131, and good candidate for replacing conventional fiducials/spacers.

Recent Advances in Polyanhydride Based Biomaterials

This review focusses on recent developments of polyanhydrides, a class of degradable synthetic biopolymers. Polyanhydrides have been used as carriers for controlled delivery of drugs. A polyanhydride copolymer of carboxyphenoxy propane and sebacic acid has been used in Gliadel brain tumor implants for the controlled delivery of carmustine or bis-chloroethylnitrosourea. They are easy and inexpensive to synthesize (especially scale up). However, polyanhydrides possess a short shelf-life. Hydrolytic cleavage and anhydride interchanges lower their molecular weights during storage. One of the highlights in recent developments of polyanhydride chemistry is the discovery of alternating copolymers having extended shelf-life. Other highlights include their applications in biomedical electronics, vaccine delivery, and nano/micro particulate delivery systems. This review examines approaches for polyanhydride synthesis followed by their recent developments in biomedical applications.

Current development of biodegradable polymeric materials for biomedical applications

In the last half-century, the development of biodegradable polymeric materials for biomedical applications has advanced significantly. Biodegradable polymeric materials are favored in the development of therapeutic devices, including temporary implants and three-dimensional scaffolds for tissue engineering. Further advancements have occurred in the utilization of biodegradable polymeric materials for pharmacological applications such as delivery vehicles for controlled/sustained drug release. These applications require particular physicochemical, biological, and degradation properties of the materials to deliver effective therapy. As a result, a wide range of natural or synthetic polymers able to undergo hydrolytic or enzymatic degradation is being studied for biomedical applications. This review outlines the current development of biodegradable natural and synthetic polymeric materials for various biomedical applications, including tissue engineering, temporary implants, wound healing, and drug delivery.

Treatment of neurodegenerative disorders through the blood-brain barrier using nanocarriers

Neurodegenerative diseases refer to disorders of the central nervous system (CNS) that are caused by neuronal degradations, dysfunctions, or death. Alzheimer's disease, Parkinson's disease, and Huntington's disease (APHD) are regarded as the three major neurodegenerative diseases. There is a vast body of literature on the causes and treatments of these neurodegenerative diseases. However, the main obstacle in developing an effective treatment strategy is the permeability of the treatment components at the blood-brain barrier (BBB). Several strategies have been developed to improve this obstruction. For example, nanomaterials facilitate drug delivery to the BBB due to their size. They have been used widely in nanomedicine and as nanoprobes for diagnosis purposes among others in neuroscience. Nanomaterials in different forms, such as nanoparticles, nanoemulsions, solid lipid nanoparticles (SLN), and liposomes, have been used to treat neurodegenerative diseases. This review will cover the basic concepts and applications of nanomaterials in the therapy of APHD.

Polyphenolic Phytochemicals in Cancer Prevention and Therapy: Bioavailability versus Bioefficacy

Natural polyphenols are organic chemicals which contain phenol units in their structures. They show antitumor properties. However, a key problem is their short half-life and low bioavailability under in vivo conditions. Still, definitively demonstrating the human benefits of isolated polyphenolic compounds (alone or in combination) using modern scientific methodology has proved challenging. The most common discrepancy between experimental and clinical observations is the use of nonphysiologically relevant concentrations of polyphenols in mechanistic studies. Thus, it remains highly controversial how applicable underlying mechanisms are with bioavailable concentrations and biological half-life. The present Perspective analyses proposed antitumor mechanisms, in vivo reported antitumor effects, and possible mechanisms that may explain discrepancies between bioavailability and bioefficacy. Polyphenol metabolism and possible toxic side effects are also considered. Our main conclusion emphasizes that these natural molecules (and their chemical derivatives) indeed can be very useful, not only as cancer chemopreventive agents but also in oncotherapy.

The effect of polyanhydride chemistry in particle-based cancer vaccines on the magnitude of the anti-tumor immune response

The goal of this research was to study the effect of polyanhydride chemistry on the immune response induced by a prophylactic cancer vaccine based on biodegradable polyanhydride particles. To achieve this goal, different compositions of polyanhydride copolymers based on 1,8-bis-(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG), 1,6-bis-(p-carboxyphenoxy)-hexane (CPH), and sebacic anhydride (SA) were synthesized by melt polycondensation, and polyanhydride copolymer particles encapsulating a model antigen, ovalbumin (OVA), were then synthesized using a double emulsion solvent evaporation technique. The ability of three different compositions of polyanhydride copolymers (50:50 CPTEG:CPH, 20:80 CPTEG:CPH, and 20:80 CPH:SA) encapsulating OVA to elicit immune responses was investigated. In addition, the impact of unmethylated oligodeoxynucleotides containing deoxycytidyl-deoxyguanosine dinucleotides (CpG ODN), an immunological adjuvant, on the immune response was also studied. The immune response to cancer vaccines was measured after treatment of C57BL/6J mice with two subcutaneous injections, seven days apart, of 50μg OVA encapsulated in particles composed of different polyanhydride copolymers with or without 25μg CpG ODN. In vivo studies showed that 20:80 CPTEG:CPH particles encapsulating OVA significantly stimulated the highest level of CD8⁺ T lymphocytes, generated the highest serum titers of OVA-specific IgG antibodies, and provided longer protection against tumor challenge with an OVA-expressing thymoma cell line in comparison to formulations made from other polyanhydride copolymers. The results also revealed that vaccination with CpG ODN along with polyanhydride particles encapsulating OVA did not enhance the immunogenicity of OVA. These results accentuate the crucial role of the copolymer composition of polyanhydrides in stimulating the immune response and provide important insights on rationally designing efficacious cancer vaccines.

STATEMENT OF SIGNIFICANCE

Compared to soluble cancer vaccine formulations, tumor antigens encapsulated in biodegradable polymeric particles have been shown to sustain antigen release and provide long-term protection against tumor challenge by improving the immune response towards the antigen. Treatment of mice with cancer vaccines based on different polyanhydride copolymers encapsulating OVA resulted in stimulation of tumor-specific immune responses with different magnitudes. This clearly indicates that polyanhydride chemistry plays a substantial role in stimulating the immune response. Vaccination with 20:80 CPTEG:CPH/OVA, the most hydrophobic formulation, stimulated the strongest cellular and humoral immune responses and provided the longest survival outcome without adding any other adjuvant. The most important finding in this study is that the copolymer composition of polyanhydride particle-based vaccines can have a direct effect on the magnitude of the antitumor immune response and should be selected carefully in order to achieve optimal cancer vaccine efficacy.

Design of novel injectable in-situ forming scaffolds for non-surgical treatment of periapical lesions: In-vitro and in-vivo evaluation

Periapical lesions are considered one of the common pathological conditions affecting alveolar bone. The primary focus of this study was to investigate the effectiveness of formulating an injectable in-situ forming scaffold-loaded with risedronate (bone resorption inhibitor) and with lornoxicam (anti-inflammatory drug) for the non-surgical treatment of periapical lesions. The scaffolds were prepared using solvent-induced phase inversion technique. Two insoluble copolymers were investigated namely; PLGA (ester-terminal) and PLGA-A (acid-terminal), additionally, SAIB was added as a high viscosity water-insoluble carrier. The addition of porogenic agents like hydrolyzed collagen was also investigated. The prepared scaffolds were characterized by analyzing their in-vitro release, DSC and rheological properties, besides their morphological properties. The results showed that the scaffolds prepared using 30% (w/v) PLGA or combined PLGA: SAIB (1:1, w/w) with total polymer concentration of 30% (w/v) possessed the most sustained drug release profile. Selected scaffolds were tested for their therapeutic effect to study the effect of porogenic agent, anti-inflammatory drug and risedronate in periapical lesions induced in dogs' teeth. Results declared that the selected scaffolds succeeded in improving the inflammation and enhancing the formation of new bony regions confirming the success of the prepared scaffolds as an innovative approach in the treatment of bone defects.

A transferrin variant as the targeting ligand for polymeric nanoparticles incorporated in 3-D PLGA porous scaffolds

We have developed doxorubicin (DOX)-loaded poly(lactide-co-glycolide) (PLGA) nanoparticles (DP) conjugated with polyethylene glycol (PEG) and transferrin (Tf) to form Tf-PEG-DPs (TPDPs), and incorporated these TPDPs into three-dimensional (3-D) PLGA porous scaffolds to form a controlled delivery system. To our knowledge, this represents the first use of a Tf variant (oxalate Tf) to improve the targeted delivery of drug-encapsulated nanoparticles (NPs) in PLGA scaffolds to PC3 prostate cancer cells. The PLGA scaffolds with TPDPs incorporated have been shown to release drugs for sustained delivery and provided a continuous release of DOX. The MTS assay was also performed to determine the potency of native and oxalate TPDPs, and a 3.0-fold decrease in IC₅₀ values were observed between the native and oxalate TPDPs. The lower IC₅₀ value for the oxalate version signifies greater potency compared to the native version, since a lower concentration of drug was required to achieve the same therapeutic effect. These results suggest that this technology has potential to become a new implantable polymeric device to improve the controlled and targeted drug delivery of Tf-conjugated NPs for cancer therapy.

Synthesis and Characterization of Salicylic Acid-Based Poly(Anhydride-Ester) Copolymers

A series of poly(anhydride-esters) based on poly(1,10-bis(o-car-boxyphenoxy)decanoate) (CPD) and poly(1,6-bis(p-carboxyphenoxy)hexane) (p-CPH) were synthesized by melt-condensation polymerization. Poly-(anhydride-esters) that contain CPD hydrolytically degraded into salicylic acid, however, these homopolymers have mechanical and thermal characteristics that limit their use in clinical applications. The synthesis and characterization of copolymers of CPD with p-CPH, a monomer known to generate mechanically stable homopolymers, was investigated. By changing the CPD to p-CPH monomer ratios, the salicylic acid loading and thermal/mechanical properties of the copolymers was a controlling factor; increasing the CPD concentration increased the salicylate loading but decreased the polymer stability; whereas increasing the p-CPH concentration increased the thermal and mechanical stability of the copolymers. Specifically, decreasing the CPD:p-CPH ratio resulted in lower salicylate loading and increased thermal decomposition temperatures. The glass transition temperatures (°C) varied from 27 to 38°C, a desirable range for elastomeric biomedical implants.

Preparation and evaluation of rotigotine-loaded implant for the treatment of Parkinson's disease and its evolution study

Purpose

To develop rotigotine-loaded implants (RI) to achieve continuous release of rotigotine for long duration for the treatment of Parkinson’s disease (PD).

Methods

RI was prepared by hot-melt extrusion method using poly (lactide-co-glycolide) (PLGA) as the matrix. In vitro drug release was optimized by drug loading, melting temperature during preparing process and additives. The surface and internal morphology of RI was imaged by SEM. The in vivo release profile of RI was investigated on rat.

Results

RI prepared with PLGA 7525 5A showed sustained release of 40 days while suffering a lag phase, which was significantly shortened by blending 5050 2A and mannitol in the matrix. RI prepared by 7525 5A/5050 2A/mannitol = 55:10:5 (rotigotine 30%) showed a 40-day sustained release in vivo with no lag phase. The drug release from RI was also affected by drug loading and melting temperature probably due to the drug state existed in the implant. The evolution of implants during release process was correlated well with the drug release kinetics.

Conclusion

RI could achieve sustained drug release for 40 days which could supply an alternative of continuous dopaminergic stimulation (CDS) for the treatment of PD.

Implantable and transdermal polymeric drug delivery technologies for the treatment of central nervous system disorders

The complexity of the brain and the membranous blood-brain barrier (BBB) has proved to be a significant limitation to the systemic delivery of pharmaceuticals to the brain rendering them sub-therapeutic and ineffective in the treatment of neurological diseases. Apart from this, lack of innovation in product development to counteract the problem is also a major contributing factor to a poor therapeutic outcome. Various innovative strategies show potential in treating some of the neurological disorders; however, drug delivery remains the most popular. To attain therapeutic drug levels in the central nervous system, large, intolerable systemic doses are generally administered. The major factors responsible for the success maintenance therapy of neurological diseases included controlled and sustained release of neurotherapeutics, reduced frequency of administration, higher bioavailability, and patient compliances. Conventional oral or injectable formulations cannot satisfy all the requirements in many circumstances. This article reviews the therapeutic implantable polymeric and transdermal devices employed in an attempt to effectively achieve therapeutic quantities of drug across the BBB over a prolonged period, to improve patient disease prognosis.

Biodegradable system for drug delivery of hydrolytically labile azanucleoside drugs

BACKGROUND

The archetypal DNA methyltransferase inhibitors, 5-azacytidine (AZA) and 5-aza-2'-deoxycytidine (DAC) are potent antineoplastic agents used in the treatment of mainly, blood malignancies. However, the administration of these drugs is confounded by their hydrolytic lability which decreases plasma circulation time. Here, we describe a new biodegradable, polyanhydride formulation for drug delivery that circumvents this drawback.

METHODS

Injectable/implantable polymeric microbeads containing dispersed microcrystals of hydrophilic AZA or DAC packed in a dry environment are protected from hydrolysis, until the hydrolytic zone reaches the core. Diclofenac is embedded into the formulation to decrease any local inflammation. The efficacy of the formulations was confirmed by monitoring the induced demethylation, and cytostatic/cytotoxic effects of continuous drug release from the time-course dissolution of the microbeads, using an in vitro developed cell based reporter system.

RESULTS

Poly(sebaccic acid-co-1,4-cyclohexanedicarboxylic acid) containing 30 wt. % drug showed zero-order release (R(2) = 0.984 for linear regression), and release rate of 10.0 %/h within the first 5 h, and subsequent slower release of the remaining drug, thus maintaining the level of drugs in the outer environment considerably longer than the typical plasma half-life of free azanucleosides. At lower concentrations, the differences between powder drug formulations and microbeads were very low or negligible, however, at higher concentrations, we discovered equivalent or increasing effects of the drugs loaded in microbeads.

CONCLUSIONS

The study provides evidence that microbead formulations of the hydrolytically labile azanucleoside drugs could prevent their chemical decomposition in aqueous solution, and effectively increase plasma circulation time.

Physical insights into salicylic acid release from poly(anhydrides)

Salicylic acid (SA) based biodegradable polyanhydrides (PAHs) are of great interest for drug delivery in a variety of diseases and disorders owing to the multi-utility of SA. There is a need for the design of SA-based PAHs for tunable drug release, optimized for the treatment of different diseases. In this study, we devised a simple strategy for tuning the release properties and erosion kinetics of a family of PAHs. PAHs incorporating SA were derived from related aliphatic diacids, varying only in the chain length, and prepared by simple melt condensation polymerization. Upon hydrolysis induced erosion, the polymer degrades into cytocompatible products, including the incorporated bioactive SA and diacid. The degradation follows first order kinetics with the rate constant varying by nearly 25 times between the PAH obtained with adipic acid and that with dodecanedioic acid. The release profiles have been tailored from 100% to 50% SA release in 7 days across the different PAHs. The release rate constants of these semi-crystalline, surface eroding PAHs decreased almost linearly with an increase in the diacid chain length, and varied by nearly 40 times between adipic acid and dodecanedioic acid PAH. The degradation products with SA concentration in the range of 30-350 ppm were used to assess cytocompatibility and showed no cytotoxicity to HeLa cells. This particular strategy is expected to (a) enable synthesis of application specific PAHs with tunable erosion and release profiles; (b) encompass a large number of drugs that may be incorporated into the PAH matrix. Such a strategy can potentially be extended to the controlled release of other drugs that may be incorporated into the PAH backbone and has important implications for the rational design of drug eluting bioactive polymers.

Synthesis and Controlled Release Behavior of Biodegradable Polymers with Pendant Ibuprofen Group

The continuous use of nonsteroidal anti-inflammatory drugs such as ibuprofen frequently leads to some serious side-effects including stomach ulcers and bleeding. In this paper, two kinds of new biocompatible polyesters (PIGB, PIGH) and polyester-amide (PIGA) comprising biodegradable components (L-glutamic acid,1,4-butanediol, and1,6-hexanediol and6-amino hexanol) and ibuprofen as pendant group have been prepared by the melting polycondensation. The chemical structures of the monomer and polymers are characterized by FTIR,1H NMR spectrum, GPC, and contact angle measurements. The drug loading of ibuprofen reaches very high level (35–37%) for PIGB, PIGH, and PIGA carriers. The free ibuprofen molecules are releasedin vitrofrom polymer carriers in a controlled manner without a burst release, different from the release pattern observed in the other drug-encapsulated systems. It is also found that the different hydrophilicity among PIGB, PIGH, and PIGA plays a key role in the time-controlled release of ibuprofen. In addition, the viability of HeLa cells after 48 h of incubation reaches more than 100%, indicating no cytotoxicity for PIGB, PIGH, and PIGA carriers.

Polyanhydrides: Synthesis, Properties, and Applications

This review focusses on polyanhydrides, a fascinating class of degradable polymers that have been used in and investigated for many bio-related applications because of their degradability and capacity to undergo surface erosion. This latter phenomenon is driven by hydrolysis of the anhydride moieties at the surface and high hydrophobicity of the polymer such that degradation and mass loss (erosion) occur before water can penetrate deep within the bulk of the polymer. As such, when surface-eroding polymers are used as therapeutic delivery vehicles, the rate of delivery is often controlled by the rate of polymer erosion, providing predictable and controlled release rates that are often zero-order. These desirable attributes are heavily influenced by polymer composition and morphology, and therefore also monomer structure and polymerization method. This review examines approaches for polyanhydride synthesis, discusses their general thermomechanical properties, surveys their hydrolysis and degradation processes along with their biocompatibility, and looks at recent developments and uses of polyanhydrides in drug delivery, stimuli-responsive materials, and novel nanotechnologies.

Biomaterials approaches to treating implant-associated osteomyelitis

Orthopaedic devices are the most common surgical devices associated with implant-related infections and Staphylococcus aureus (S. aureus) is the most common causative pathogen in chronic bone infections (osteomyelitis). Treatment of these chronic bone infections often involves combinations of antibiotics given systemically and locally to the affected site via a biomaterial spacer. The gold standard biomaterial for local antibiotic delivery against osteomyelitis, poly(methyl methacrylate) (PMMA) bone cement, bears many limitations. Such shortcomings include limited antibiotic release, incompatibility with many antimicrobial agents, and the need for follow-up surgeries to remove the non-biodegradable cement before surgical reconstruction of the lost bone. Therefore, extensive research pursuits are targeting alternative, biodegradable materials to replace PMMA in osteomyelitis applications. Herein, we provide an overview of the primary clinical treatment strategies and emerging biodegradable materials that may be employed for management of implant-related osteomyelitis. We performed a systematic review of experimental biomaterials systems that have been evaluated for treating established S. aureus osteomyelitis in an animal model. Many experimental biomaterials were not decisively more efficacious for infection management than PMMA when delivering the same antibiotic. However, alternative biomaterials have reduced the number of follow-up surgeries, enhanced the antimicrobial efficacy by delivering agents that are incompatible with PMMA, and regenerated bone in an infected defect. Understanding the advantages, limitations, and potential for clinical translation of each biomaterial, along with the conditions under which it was evaluated (e.g. animal model), is critical for surgeons and researchers to navigate the plethora of options for local antibiotic delivery.

Salicylic acid (SA) bioaccessibility from SA-based poly(anhydride-ester)

The bioaccessibility of salicylic acid (SA) can be effectively modified by incorporating the pharmacological compound directly into polymers such as poly(anhydride-esters). After simulated digestion conditions, the bioaccessibility of SA was observed to be statistically different (p < 0.0001) in each sample: 55.5 ± 2.0% for free SA, 31.2 ± 2.4% the SA-diglycolic acid polymer precursor (SADG), and 21.2 ± 3.1% for SADG-P (polymer). The release rates followed a zero-order release rate that was dependent on several factors, including (1) solubilization rate, (2) macroscopic erosion of the powdered polymer, (3) hydrolytic cleavage of the anhydride bonds, and (4) subsequent hydrolysis of the polymer precursor (SADG) to SA and diglycolic acid.

Radiofrequency-triggered release for on-demand delivery of therapeutics from titania nanotube drug-eluting implants

Aim: This study aimed to demonstrate radiofrequency (RF)-triggered release of drugs and drug carriers from drug-eluting implants using gold nanoparticles as energy transducers. Materials & methods: Titanium wire with a titania nanotube layer was used as an implant loaded with indomethacin and micelles (tocopheryl PEG succinate) as a drug and drug carrier model. RF signals were generated from a customized RF generator to trigger in vitro release. Results & discussion: Within 2.5 h, 18 mg (92%) of loaded drug and 14 mg (68%) of loaded drug carriers were released using short RF exposure (5 min), compared with 5 mg (31%) of drug and 2 mg (11%) of drug carriers without a RF trigger. Gold nanoparticles can effectively function as RF energy transducers inside titania nanotubes for rapid release of therapeutics at arbitrary times. Conclusion: The results of this study show that RF is a promising strategy for triggered release from implantable drug delivery systems where on-demand delivery of therapeutics is required.

Original submitted 19 November 2012; Revised submitted 1 April 2013

Synthetic biodegradable functional polymers for tissue engineering: a brief review

Scaffolds play a crucial role in tissue engineering. Biodegradable polymers with great processing flexibility are the predominant scaffolding materials. Synthetic biodegradable polymers with well-defined structure and without immunological concerns associated with naturally derived polymers are widely used in tissue engineering. The synthetic biodegradable polymers that are widely used in tissue engineering, including polyesters, polyanhydrides, polyphosphazenes, polyurethane, and poly (glycerol sebacate) are summarized in this article. New developments in conducting polymers, photoresponsive polymers, amino-acid-based polymers, enzymatically degradable polymers, and peptide-activated polymers are also discussed. In addition to chemical functionalization, the scaffold designs that mimic the nano and micro features of the extracellular matrix (ECM) are presented as well, and composite and nanocomposite scaffolds are also reviewed.

Bioerodible system for sequential release of multiple drugs

Because many complex physiological processes are controlled by multiple biomolecules, comprehensive treatment of certain disease conditions may be more effectively achieved by administration of more than one type of drug. Thus, the objective of the present research was to develop a multilayered, polymer-based system for sequential delivery of multiple drugs. The polymers used were cellulose acetate phthalate (CAP) complexed with Pluronic F-127 (P). After evaluating morphology of the resulting CAPP system, in vitro release of small molecule drugs and a model protein was studied from both single and multilayered devices. Drug release from single-layered CAPP films followed zero-order kinetics related to surface erosion of the association polymer. Release studies from multilayered CAPP devices showed the possibility of achieving intermittent release of one type of drug as well as sequential release of more than one type of drug. Mathematical modeling accurately predicted the release profiles for both single layer and multilayered devices. The present CAPP association polymer-based multilayer devices can be used for localized, sequential delivery of multiple drugs for the possible treatment of complex disease conditions, and perhaps for tissue engineering applications, that require delivery of more than one type of biomolecule.

Biodegradable polyesters containing ibuprofen and naproxen as pendant groups

Controlled release of nonsteroidal anti-inflammatory drugs such as ibuprofen and naproxen could be beneficial for the treatment of inflammatory diseases while reducing the side effects resulting from their continuous use. Novel biodegradable polyesters solely comprised of biocompatible components (e.g., tartaric acid, 1,8-octanediol, and ibuprofen or naproxen as pendant groups) have been synthesized using tin(II) 2-ethylhexanoate as catalyst at 130 °C and subsequently characterized to determine their structures and physicochemical properties. The polymers release the free drug (ibuprofen or naproxen) in vitro in a controlled manner without burst release, unlike the release rates achieved when the drugs are encapsulated in other polymers. These new biomaterials are not cytotoxic toward mouse fibroblasts up to 0.10 mg/mL. The drugs retain their chemical structure following hydrolytic degradation of the polymer, suggesting that bioactivity is preserved.

Novel 4-arm poly(ethylene glycol)-block-poly(anhydride-esters) amphiphilic copolymer micelles loading curcumin: preparation, characterization, and in vitro evaluation

A novel 4-arm poly(ethylene glycol)-block-poly(anhydride-esters) amphiphilic copolymer (4-arm PEG-b-PAE) was synthesized by esterization of 4-arm poly(ethylene glycol) and poly(anhydride-esters) which was obtained by melt polycondensation of α -, ω -acetic anhydride terminated poly(L-lactic acid). The obtained 4-arm PEG-b-PAE was characterized by (1)H-NMR and gel permeation chromatography. The critical micelle concentration of 4-arm PEG-b-PAE was 2.38 μg/mL. The curcumin-loaded 4-arm PEG-b-PAE micelles were prepared by a solid dispersion method and the drug loading content and encapsulation efficiency of the micelles were 7.0% and 85.2%, respectively. The curcumin-loaded micelles were spherical with a hydrodynamic diameter of 151.9 nm. Curcumin was encapsulated within 4-arm PEG-b-PAE micelles amorphously and released from the micelles, faster in pH 5.0 than pH 7.4, presenting one biphasic drug release pattern with rapid release at the initial stage and slow release later. The hemolysis rate of the curcumin-loaded 4-arm PEG-b-PAE micelles was 3.18%, which was below 5%. The IC50 value of the curcumin-loaded micelles against Hela cells was 10.21 μg/mL, lower than the one of free curcumin (25.90 μg/mL). The cellular uptake of the curcumin-loaded micelles in Hela cell increased in a time-dependent manner. The curcumin-loaded micelles could induce G2/M phase cell cycle arrest and apoptosis of Hela cells.

Real-time and in situ drug release monitoring from nanoporous implants under dynamic flow conditions by reflectometric interference spectroscopy

Herein, we present an innovative approach to monitoring in situ drug release under dynamic flow conditions from aluminum implants featuring nanoporous anodic alumina (NAA) covers used as a model of drug-releasing implants. In this method, reflectometric interference spectroscopy (RIfS) is used to monitor in real-time the diffusion of drug from these nanoporous implants. The release process is carried out in a microfluidic device, which makes it possible to analyze drug release under dynamic flow conditions with constant refreshing of eluting medium. This setup mimics the physiological conditions of biological milieu at the implant site inside the host body. The release of a model drug, indomethacin, is established by measuring the optical thickness change with time under four different flow rates (i.e. 0, 10, 30, and 50 μL min(-1)). The obtained data are fitted by a modified Higuchi model, confirming the diffusion-controlled release mechanism. The obtained release rate constants demonstrate that the drug release depends on the flow rate and the faster the flow rate the higher the drug release from the nanoporous covers. In particular, the rate constants increase from 2.23 ± 0.02 to 12.47 ± 0.04 μg min(-1/2) when the flow rate is increased from 10 to 50 μL min(-1), respectively. Therefore, this method provides more reliable and relevant information than conventional in vitro drug release methods performed under static conditions.

Combinatorial evaluation of in vivo distribution of polyanhydride particle-based platforms for vaccine delivery

Several challenges are associated with current vaccine strategies, including repeated immunizations, poor patient compliance, and limited approved routes for delivery, which may hinder induction of protective immunity. Thus, there is a need for new vaccine adjuvants capable of multi-route administration and prolonged antigen release at the site of administration by providing a depot within tissue. In this work, we designed a combinatorial platform to investigate the in vivo distribution, depot effect, and localized persistence of polyanhydride nanoparticles as a function of nanoparticle chemistry and administration route. Our observations indicated that the route of administration differentially affected tissue residence times. All nanoparticles rapidly dispersed when delivered intranasally but provided a depot when administered parenterally. When amphiphilic and hydrophobic nanoparticles were administered intranasally, they persisted within lung tissue. These results provide insights into the chemistry- and route-dependent distribution and tissue-specific association of polyanhydride nanoparticle-based vaccine adjuvants.

Silicon micro- and nanofabrication for medicine

This manuscript constitutes a review of several innovative biomedical technologies fabricated using the precision and accuracy of silicon micro- and nanofabrication. The technologies to be reviewed are subcutaneous nanochannel drug delivery implants for the continuous tunable zero-order release of therapeutics, multi-stage logic embedded vectors for the targeted systemic distribution of both therapeutic and imaging contrast agents, silicon and porous silicon nanowires for investigating cellular interactions and processes as well as for molecular and drug delivery applications, porous silicon (pSi) as inclusions into biocomposites for tissue engineering, especially as it applies to bone repair and regrowth, and porous silica chips for proteomic profiling. In the case of the biocomposites, the specifically designed pSi inclusions not only add to the structural robustness, but can also promote tissue and bone regrowth, fight infection, and reduce pain by releasing stimulating factors and other therapeutic agents stored within their porous network. The common material thread throughout all of these constructs, silicon and its associated dielectrics (silicon dioxide, silicon nitride, etc.), can be precisely and accurately machined using the same scalable micro- and nanofabrication protocols that are ubiquitous within the semiconductor industry. These techniques lend themselves to the high throughput production of exquisitely defined and monodispersed nanoscale features that should eliminate architectural randomness as a source of experimental variation thereby potentially leading to more rapid clinical translation.

Subcutaneous administration of nano- and microsuspensions of poorly soluble compounds to rats

The aim of the present study was to evaluate and interpret the pharmacokinetic profiles of two compounds after subcutaneous (s.c.) administration. The compounds have similar physicochemical properties, but are a base (BA99) and an acid (AC88), respectively. The compounds were administered as nano- (5 and 500 µmol/kg) and microsuspensions (5 µmol/kg) s.c. to Sprague-Dawley rats. At the low dose, the exposure was higher for both compounds administered as nanocrystals compared to microparticles. The high dose of the compounds resulted in even higher exposure, but not in a dose-linear manner. The differences in exposure between nano- and microparticles were mainly ascribed to higher dissolution rate and improved solubility for smaller particles. In addition to differences in exposure, there were also differences in the elimination pattern. After s.c. injection of 5 µmol/kg of BA99 as nano- and microsuspensions, the elimination profile was similar as observed earlier after oral administration. However, after injection of the higher dose of BA99 and all formulations of AC88, an extended elimination profile was observed, forming a maintained plateau under the investigated time-period. Essentially, constant plasma levels were caused by a balanced equilibrium between total body clearance of the drug and supply rate of drug from the formulations.

Tunable drug release profiles from salicylate-based poly(anhydride-ester) matrices using small molecule admixtures

Poly(anhydride-esters) with salicylic acid, a nonsteroidal anti-inflammatory drug, chemically incorporated into the polymer backbone provide high inherent drug loading. These poly(anhydride-esters) hydrolytically degrade to release salicylic acid over extended time periods (>30 days); however, an initial lag period of no salicylic acid release is observed. This lag period could be unfavorable in applications where immediate salicylic acid release is desired. Poly(anhydride-esters) with short (2 days) and long (11 days) lag periods were admixed with various small molecules as a means to shorten or eliminate the lag period. Salicylic acid, larger salicylic acid prodrugs, and 1:1 combinations of the two were physically admixed, each at 1%, 5%, and 10% (w/w). All admixtures resulted in immediate salicylic acid release and a decrease in glass transition temperatures compared to polymer alone. By varying the amounts of salicylic acid and salicylic acid prodrugs incorporated into the polymer matrix, immediate and constant salicylic acid release profiles over varied time periods were achieved.