Polymeric implants for cancer chemotherapy

G-POSS connected double network starch gels for protein release

Starch is one of the most frequently preferred natural polymers in hydrogel synthesis. Herein, we combined two strategies of associating brittle and ductile networks in a structure and incorporating inorganic particles into the polymeric gel to design mechanically enhanced nanocomposite double network (DN) starch gels. For the first time in the literature, nanocomposite starch gels (s-NC) were designed by cross-linking starch chains with 8-armed glycidyl-polyhedral oligomeric silsesquioxane (g-POSS) units. Fourier Transform Infrared Spectroscopy and Energy Dispersive X-Ray Spectroscopy analyses have proven that g-POSS is included in the gel structure and is homogeneously distributed throughout the network. More stable d-NC-DMA and d-NC-VP gels were obtained by incorporating N,N-dimethylacrylamide (DMA), or 1-vinyl-2-pyrrolidinone (VP) units, respectively, into g-POSS-linked starch gels, and the reaction kinetics were followed in situ. In SEM images, it was observed that d-NC-DMA had smaller pores and thicker pore walls compared to s-NC and d-NC-VP starch gels, and its mechanical strength was shown to be much superior by rheological tests, compression, and tensile analyses. In addition to increasing the mechanical strength of the gels, the potential of starch in protein release applications using amylase sensitivity has been demonstrated in vitro experiments using the model protein BSA.

Micro- and Nanostructured Fibrous Composites via Electro-Fluid Dynamics: Design and Applications for Brain

The brain consists of an interconnected network of neurons tightly packed in the extracellular matrix (ECM) to form complex and heterogeneous composite tissue. According to recent biomimicry approaches that consider biological features as active components of biomaterials, designing a highly reproducible microenvironment for brain cells can represent a key tool for tissue repair and regeneration. Indeed, this is crucial to support cell growth, mitigate inflammation phenomena and provide adequate structural properties needed to support the damaged tissue, corroborating the activity of the vascular network and ultimately the functionality of neurons. In this context, electro-fluid dynamic techniques (EFDTs), i.e., electrospinning, electrospraying and related techniques, offer the opportunity to engineer a wide variety of composite substrates by integrating fibers, particles, and hydrogels at different scales-from several hundred microns down to tens of nanometers-for the generation of countless patterns of physical and biochemical cues suitable for influencing the in vitro response of coexistent brain cell populations mediated by the surrounding microenvironment. In this review, an overview of the different technological approaches-based on EFDTs-for engineering fibrous and/or particle-loaded composite substrates will be proposed. The second section of this review will primarily focus on describing current and future approaches to the use of composites for brain applications, ranging from therapeutic to diagnostic/theranostic use and from repair to regeneration, with the ultimate goal of providing insightful information to guide future research efforts toward the development of more efficient and reliable solutions.

Implantation of In Situ Gelling Systems for the Delivery of Chemotherapeutic Agents

Implantation is a modern method of administering chemotherapeutic agents, with a highly targeted effect and better patient tolerance due to the low frequency of administration. Implants are capable of controlled release, which makes them a viable alternative to infusional chemotherapy, allowing patients to enjoy a better quality of life without the need for prolonged hospitalization. Compared to subcutaneous implantation, intratumoral implantation has a number of significant advantages in terms of targeting and side effects, but this area of chemotherapy is still poorly understood in terms of clinical trials. At the same time, there are more known developments of drugs in the form of implants and injections for intratumoral administration. The disadvantages of classical intratumoral implants are the need for surgical intervention to install the system and the increased risk of tumor rupture noted by some specialists. The new generation of implants are in situ implants-systems formed in the tumor due to a phase transition (sol-gel transition) under the influence of various stimuli. Among this systems some are highly selective for a certain type of malignant neoplasm. Such systems are injected and have all the advantages of intratumoral injections, but due to the phase transition occurring in situ, they form depot forms that allow the long-term release of chemotherapeutic agents.

In vivo study of the utility of selective intra-arterial injection of thiopental for neuroprotection in reversible cerebral ischemia

BACKGROUND

Neuroprotective agents are needed to reduce cerebral damage during surgical or neurointerventional procedures including stroke patients.

PURPOSE

To evaluate if thiopental can be used as a neuroprotective agent when injected intra-arterially in a transient ischemia model.

MATERIAL AND METHODS

In total, 24 rabbits were studied as four groups of six animals. Group 1 served as the control group. In group 2, transient ischemia was obtained by intracarotid administration of degradable starch microspheres (DSM). Group 3 was administered thiopental intra-arterially via the carotid artery. Group 4 (experimental group) received both thiopental and DSM intra-arterially. DSM and thiopental were administered through a microcatheter placed into the common carotid artery via the central ear artery access. After sacrifice, apoptotic cells in the cerebral tissues of the animals were evaluated in H&E and TUNEL stained slides.

RESULTS

There was a significant increase in the number of apoptotic glial or neuronal cells in group 2 compared to the control group and group 3. The mean number of both the apoptotic neuronal cells (6.8 ± 2.1 vs. 2.5 ± 1.3, P < 0.001) and the apoptotic glial cells (9.4 ± 3.1 vs. 4.6 ± 1.6, P < 0.001) were higher in group 2 compared to group 4. In addition, a higher level of neurological improvement was observed in group 4 compared to group 2 based on neurological assessment score.

CONCLUSION

The intra-arterial administration of thiopental has a protective effect on both glial and neuronal cells during temporary cerebral ischemia in low doses.

Beyond Tissue replacement: The Emerging role of smart implants in healthcare

Smart implants are increasingly used to treat various diseases, track patient status, and restore tissue and organ function. These devices support internal organs, actively stimulate nerves, and monitor essential functions. With continuous monitoring or stimulation, patient observation quality and subsequent treatment can be improved. Additionally, using biodegradable and entirely excreted implant materials eliminates the need for surgical removal, providing a patient-friendly solution. In this review, we classify smart implants and discuss the latest prototypes, materials, and technologies employed in their creation. Our focus lies in exploring medical devices beyond replacing an organ or tissue and incorporating new functionality through sensors and electronic circuits. We also examine the advantages, opportunities, and challenges of creating implantable devices that preserve all critical functions. By presenting an in-depth overview of the current state-of-the-art smart implants, we shed light on persistent issues and limitations while discussing potential avenues for future advancements in materials used for these devices.

Solid implantable devices for sustained drug delivery

Implantable drug delivery systems (IDDS) are an attractive alternative to conventional drug administration routes. Oral and injectable drug administration are the most common routes for drug delivery providing peaks of drug concentrations in blood after administration followed by concentration decay after a few hours. Therefore, constant drug administration is required to keep drug levels within the therapeutic window of the drug. Moreover, oral drug delivery presents alternative challenges due to drug degradation within the gastrointestinal tract or first pass metabolism. IDDS can be used to provide sustained drug delivery for prolonged periods of time. The use of this type of systems is especially interesting for the treatment of chronic conditions where patient adherence to conventional treatments can be challenging. These systems are normally used for systemic drug delivery. However, IDDS can be used for localised administration to maximise the amount of drug delivered within the active site while reducing systemic exposure. This review will cover current applications of IDDS focusing on the materials used to prepare this type of systems and the main therapeutic areas of application.

Advanced Nano-Carriers for Anti-Tumor Drug Loading

Chemotherapy is one of the important means of tumor therapy. However, most of the anti-tumor drugs that currently used in clinic are hydrophobic non-specific drugs, which seriously affect the efficacy of drugs. With the development of nanotechnology, drug efficacy can be improved by selecting appropriate biodegradable nanocarriers for achieving the controlled release, targeting and higher bioavailability of drugs. This paper reviewed the research progress of anti-tumor drug nanoparticle carriers, which mainly summarized the materials used for anti-tumor drug nanoparticle carriers and their effects in anti-tumor drugs, as well as the targeted drug delivery methods of anti-tumor drugs based on nanocarriers.

Polymeric long-acting drug delivery systems (LADDS) for treatment of chronic diseases: Inserts, patches, wafers, and implants

Non-oral long-acting drug delivery systems (LADDS) encompass a range of technologies for precisely delivering drug molecules into target tissues either through the systemic circulation or via localized injections for treating chronic diseases like diabetes, cancer, and brain disorders as well as for age-related eye diseases. LADDS have been shown to prolong drug release from 24 h up to 3 years depending on characteristics of the drug and delivery system. LADDS can offer potentially safer, more effective, and patient friendly treatment options compared to more invasive modes of drug administration such as repeated injections or minor surgical intervention. Whilst there is no single technology or definition that can comprehensively embrace LADDS; for the purposes of this review, these systems include solid implants, inserts, transdermal patches, wafers and in situ forming delivery systems. This review covers common chronic illnesses, where candidate drugs have been incorporated into LADDS, examples of marketed long-acting pharmaceuticals, as well as newly emerging technologies, used in the fabrication of LADDS.

Use of 3D Printing for the Development of Biodegradable Antiplatelet Materials for Cardiovascular Applications

Small-diameter synthetic vascular grafts are required for surgical bypass grafting when there is a lack of suitable autologous vessels due to different reasons, such as previous operations. Thrombosis is the main cause of failure of small-diameter synthetic vascular grafts when used for this revascularization technique. Therefore, the development of biodegradable vascular grafts capable of providing a localized and sustained antithrombotic drug release mark a major step forward in the fight against cardiovascular diseases, which are the leading cause of death globally. The present paper describes the use of an extrusion-based 3D printing technology for the production of biodegradable antiplatelet tubular grafts for cardiovascular applications. For this purpose, acetylsalicylic acid (ASA) was chosen as a model molecule due to its antiplatelet activity. Poly(caprolactone) and ASA were combined for the fabrication and characterization of ASA-loaded tubular grafts. Moreover, rifampicin (RIF) was added to the formulation containing the higher ASA loading, as a model molecule that can be used to prevent vascular prosthesis infections. The produced tubular grafts were fully characterized through multiple techniques and the last step was to evaluate their drug release, antiplatelet and antimicrobial activity and cytocompatibility. The results suggested that these materials were capable of providing a sustained ASA release for periods of up to 2 weeks. Tubular grafts containing 10% (w/w) of ASA showed lower platelet adhesion onto the surface than the blank and grafts containing 5% (w/w) of ASA. Moreover, tubular grafts scaffolds containing 1% (w/w) of RIF were capable of inhibiting the growth of Staphylococcus aureus. Finally, the evaluation of the cytocompatibility of the scaffold samples revealed that the incorporation of ASA or RIF into the composition did not compromise cell viability and proliferation at short incubation periods (24 h).

Polymeric Composite Matrix with High Biobased Content as Pharmaceutically Relevant Molecular Encapsulation and Release Platform

Drug delivery systems (DDS) that can temporally control the rate and extent of release of therapeutically active molecules find applications in many clinical settings, ranging from infection control to cancer therapy. With an aim to design a locally implantable, controlled-release DDS, we demonstrated the feasibility of using cellulose nanocrystal (CNC)-reinforced poly (l-lactic acid) (PLA) composite beads. The performance of the platform was evaluated using doxorubicin (DOX) as a model drug for applications in triple-negative breast cancer. A facile, nonsolvent-induced phase separation (NIPS) method was adopted to form composite beads. We observed that CNC loading within these beads played a critical role in the mechanical stability, porosity, water uptake, diffusion, release, and pharmacological activity of the drug from the delivery system. When loaded with DOX, composite beads significantly controlled the release of the drug in a pH-dependent pattern. For example, PLA/CNC beads containing 37.5 wt % of CNCs showed a biphasic release of DOX, where 41 and 82% of the loaded drug were released at pH 7.4 and pH 5.5, respectively, over 7 days. Drug release followed Korsmeyer's kinetics, indicating that the release mechanism was mostly diffusion and swelling-controlled. We showed that DOX released from drug-loaded PLA/CNC composite beads locally suppressed the growth and proliferation of triple-negative breast cancer cells, MBA-MB-231, via the apoptotic pathway. The efficacy of the DDS was evaluated in human tissue explants. We envision that such systems will find applications for designing biobased platforms with programmed stability and drug delivery functions.

Polymeric drug delivery systems by additive manufacturing

Additive manufacturing (AM) is gaining interests in drug delivery applications, offering innovative opportunities for the design and development of systems with complex geometry and programmed controlled release profile. In addition, polymer-based drug delivery systems can improve drug safety, efficacy, patient compliance, and are the key materials in AM. Therefore, combining AM and polymers can be beneficial to overcome the existing limitations in the development of controlled release drug delivery systems. Considering these advantages, here we are focusing on the recent developments in the field of polymeric drug delivery systems prepared by AM. This review provides a comprehensive overview on a holistic polymer-AM perspective for drug delivery systems with discussion on the materials, properties, design and fabrication techniques and the mechanisms used to achieve a controlled release system. The current challenges and future perspectives for personalized medicine and clinical use of these systems are also briefly discussed.

Biodistribution of etoposide via intratumoral chemotherapy with etoposide-loaded implants

Etoposide (VP16) is the traditional antitumor agent which has been widely used in a variety of cancers. However, intravenous administration of VP16 was limited in clinical application because of its low aqueous solubility, poor bioavailability and dose-limiting adverse effects. Local chemotherapy with VP16-loaded drug delivery systems could provide a continuous release of drug at the target site, while minimizing the systemic toxicity. In this study, we prepared the poly-l-lactic acid (PLLA) based VP16-loaded implants (VP16 implants) by the direct compression method. The VP16 implants were characterized with regards to drug content, micromorphology, drug release profiles, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) analyses. Furthermore, the biodistribution of VP16 via intratumoral chemotherapy with VP16 implants was investigated using the murine Lewis lung carcinoma model. Our results showed that VP16 dispersed homogenously in the polymeric matrix. Both in vitro and in vivo drug release profiles of the implants were characterized by high initial burst release followed by sustained release of VP16. The VP16 implants showed good compatibility between VP16 and the excipients. Intratumoral chemotherapy with VP16 implants resulted in significantly higher concentration and longer duration of VP16 in tumor tissues compared with single intraperitoneal injection of VP16 solution. Moreover, we found the low level of VP16 in plasma and normal organ tissues. These results suggested that intratumoral chemotherapy with VP16 implants enabled high drug concentration at the target site and has the potential to be used as a novel method to treat cancer.

Three-Dimensional Printing of Curcumin-Loaded Biodegradable and Flexible Scaffold for Intracranial Therapy of Glioblastoma Multiforme

A novel drug delivery system preventing Glioblastoma multiforme (GBM) recurrence after resection surgery is imperatively required to overcome the mechanical limitation of the current local drug delivery system and to offer personalised treatment options for GBM patients. In this study, 3D printed biodegradable flexible porous scaffolds were developed via Fused Deposition Modelling (FDM) three-dimensional (3D) printing technology for the local delivery of curcumin. The flexible porous scaffolds were 3D printed with various geometries containing 1, 3, 5, and 7% (w/w) of curcumin, respectively, using curcumin-loaded polycaprolactone (PCL) filaments. The scaffolds were characterised by a series of characterisation studies and in vitro studies were also performed including drug release study, scaffold degradation study, and cytotoxicity study. The curcumin-loaded PCL scaffolds displayed versatile spatiotemporal characteristics. The polymeric scaffolds obtained great mechanical flexibility with a low tensile modulus of less than 2 MPa, and 4 to 7-fold ultimate tensile strain, which can avoid the mechanical mismatch problem of commercially available GLIADEL wafer with a further improvement in surgical margin coverage. In vitro release profiles have demonstrated the sustained release patterns of curcumin with adjustable release amounts and durations up to 77 h. MTT study has demonstrated the great cytotoxic effect of curcumin-loaded scaffolds against the U87 human GBM cell line. Therefore, 3D printed curcumin-loaded scaffold has great promise to provide better GBM treatment options with its mechanical flexibility and customisability to match individual needs, preventing post-surgery GBM recurrence and eventually prolonging the life expectancy of GBM patients.

Local penetration of doxorubicin via intrahepatic implantation of PLGA based doxorubicin-loaded implants

Doxorubicin (DOX) is widely used in the chemotherapy of a wide range of cancers. However, intravenous administration of DOX causes toxicity to most major organs which limits its clinical application. DOX-loaded drug delivery system could provide a continuous sustained-release of drugs and enables high drug concentrations at the target site, while reducing systemic toxicity. Additionally, local chemotherapy with DOX may be a promising approach for lowering post-surgical recurrence of cancer. In this study, the sustained-release DOX-loaded implants were prepared by melt-molding method. The implants were characterized with regards to drug content uniformity, micromorphology and drug release profiles. Furthermore, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) analyses were carried out to investigate the drug-excipient compatibility. To determine the local penetration of DOX in liver, the minipigs received intrahepatic implantation of DOX-loaded implants by abdominal surgery. UPLC-MS/MS method was used to detect the concentration of DOX in liver tissues. Our results suggested that DOX-loaded implants delivered high doses of drug at the implantation site for a prolonged period and provided valuable information for the future clinical applications of the DOX-loaded implants.

Nanomaterial-based blood-brain-barrier (BBB) crossing strategies

Increasing attention has been paid to the diseases of central nervous system (CNS). The penetration efficiency of most CNS drugs into the brain parenchyma is rather limited due to the existence of blood-brain barrier (BBB). Thus, BBB crossing for drug delivery to CNS remains a significant challenge in the development of neurological therapeutics. Because of the advantageous properties (e.g., relatively high drug loading content, controllable drug release, excellent passive and active targeting, good stability, biodegradability, biocompatibility, and low toxicity), nanomaterials with BBB-crossability have been widely developed for the treatment of CNS diseases. This review summarizes the current understanding of the physiological structure of BBB, and provides various nanomaterial-based BBB-crossing strategies for brain delivery of theranostic agents, including intranasal delivery, temporary disruption of BBB, local delivery, cell penetrating peptide (CPP) mediated BBB-crossing, receptor mediated BBB-crossing, shuttle peptide mediated BBB-crossing, and cells mediated BBB-crossing. Clinicians, biologists, material scientists and chemists are expected to be interested in this review.

Subcutaneous delivery of biotherapeutics: challenges at the injection site

INTRODUCTION

Biotherapeutics are primarily delivered subcutaneously due to better compliance and prolonged rate of absorption compared to other parenteral administration routes. Recent research has allowed for the development of biotherapeutic formulations for subcutaneous delivery that require a lower frequency of administration by increasing drug half-life. Formulations determine shelf-life stability as well as features and transient behaviors that influence stability once implanted in the subcutaneous space.

AREAS COVERED

This review provides an overview of the factors affecting subcutaneous absorption with a focus on transient effects at the injection site following administration of biotherapeutics and the subsequent impact on absorption and stability.

EXPERT OPINION

Advances have been made in understanding subcutaneous tissue and the complex interplay of factors that regulate its homeostasis. The issue of poor stability after injection has been neglected, and many biotherapeutics are hampered by low bioavailability. With the advent of new in vitro techniques that account for properties of the injection site, stability studies evaluating subcutaneous tissues and impacts on pharmacokinetics of biotherapeutics may be useful in the development of new formulations.

A personalized and long-acting local therapeutic platform combining photothermal therapy and chemotherapy for the treatment of multidrug-resistant colon tumor

BACKGROUND

Local photothermal therapy (PTT) provides an easily applicable, noninvasive adjunctive therapy for colorectal cancer (CRC), especially when multidrug resistance (MDR) occurs. However, using PTT alone does not result in complete tumor ablation in many cases, thus resulting in tumor recurrence and metastasis.

MATERIALS AND METHODS

In this study, we aim to develop a personalized local therapeutic platform combining PTT with long-acting chemotherapy for the treatment of MDR CRC. The platform consists of polyethylene glycol (PEG)-coated gold nanorods (PEG-GNRs) and D-alpha-tocopheryl PEG 1000 succinate (TPGS)-coated paclitaxel (PTX) nanocrystals (TPGS-PTX NC), followed by the incorporation into an in situ hydrogel (gel) system (GNRs-TPGS-PTX NC-gel) before injection. After administration, PEG-GNRs can exert quick and efficient local photothermal response under near-infrared laser irradiation to shrink tumor; TPGS-PTX NC then provides a long-acting chemotherapy due to the sustained release of PTX along with the P-glycoprotein inhibitor TPGS to reverse the drug resistance.

RESULTS

The cytotoxicity studies showed that the IC50 of GNRs-TPGS-PTX NC-gel with laser irradiation decreased to ~178-folds compared with PTX alone in drug-resistant SW620 AD300 cells. In the in vivo efficacy test, after laser irradiation, the GNRs-TPGS-PTX NC-gel showed similar tumor volume inhibition compared with GNRs-gel at the beginning. However, after 14 days, the tumor volume of the mice treated with GNRs-gel quickly increased, while that of the mice treated with GNRs-TPGS-PTX NC-gel remained controllable due to the long-term chemotherapeutic effect of TPGS-PTX NC. The mice treated with GNRs-TPGS-PTX NC-gel also showed no weight loss and obvious organ damages and lesions during the treatment, indicating a low systemic side effect profile and a good biocompatibility.

CONCLUSION

Overall, the nano-complex may serve as a promising local therapeutic patch against MDR CRC with one-time dosing to achieve a long-term tumor control. The doses of PEG-GNRs and TPGS-PTX NC can be easily adjusted before use according to patient-specific characteristics potentially making it a personalized therapeutic platform.

Comparing human peritoneal fluid and phosphate-buffered saline for drug delivery: do we need bio-relevant media?

An understanding of biological fluids at the site of administration is important to predict the fate of drug delivery systems in vivo. Little is known about peritoneal fluid; therefore, we have investigated this biological fluid and compared it to phosphate-buffered saline, a synthetic media commonly used for in vitro evaluation of intraperitoneal drug delivery systems. Human peritoneal fluid samples were analysed for electrolyte, protein and lipid levels. In addition, physicochemical properties were measured alongside rheological parameters. Significant inter-patient variations were observed with regard to pH (p < 0.001), buffer capacity (p < 0.05), osmolality (p < 0.001) and surface tension (p < 0.05). All the investigated physicochemical properties of peritoneal fluid differed from phosphate-buffered saline (p < 0.001). Rheological examination of peritoneal fluid demonstrated non-Newtonian shear thinning behaviour and predominantly exhibited the characteristics of an entangled network. Inter-patient and inter-day variability in the viscosity of peritoneal fluid was observed. The solubility of the local anaesthetic lidocaine in peritoneal fluid was significantly higher (p < 0.05) when compared to phosphate-buffered saline. Interestingly, the dissolution rate of lidocaine was not significantly different between the synthetic and biological media. Importantly, and with relevance to intraperitoneal drug delivery systems, the sustained release of lidocaine from a thermosensitive gel formulation occurred at a significantly faster rate into peritoneal fluid. Collectively, these data demonstrate the variation between commonly used synthetic media and human peritoneal fluid. The differences in drug release rates observed illustrate the need for bio-relevant media, which ultimately would improve in vitro-in vivo correlation.

Bacterial cellulose hydrogel loaded with lipid nanoparticles for localized cancer treatment

The use of hybrid materials, where a matrix sustains nanoparticles controlling the release of the chemotherapeutic drug, could be beneficial for the treatment of primary tumors prior or after surgery. This localized chemotherapy would guarantee high drug concentrations at the tumor site while precluding systemic drug exposure minimizing undesirable side effects. We combined bacterial cellulose hydrogel (BC) and nanostructured lipid carriers (NLCs) including doxorubicin (Dox) as a drug model. NLCs loaded with cationic Dox (NLCs-H) or neutral Dox (NLCs-N) were fully characterized and their cell internalization and cytotoxic efficacy were evaluated in vitro against MDA-MB-231 cells. Thereafter, a fixed combination of NLCs-H and NLCs-N loaded into BC (BC-NLCs-NH) was assayed in vivo into an orthotopic breast cancer mouse model. NLCs-H showed low encapsulation efficiency (48%) and fast release of the drug while NLCs-N showed higher encapsulation (97%) and sustained drug release. Both NLCs internalized via endocytic pathway, while allowing a sustained release of the Dox, which in turn rendered IC50 values below of those of free Dox. Taking advantage of the differential drug release, a mixture of NLCs-N and NLCs-H was encapsulated into BC matrix (BC-NLCs-NH) and assayed in vivo, showing a significant reduction of tumor growth, metastasis incidence and local drug toxicities.

Biomaterial scaffolds for non-invasive focal hyperthermia as a potential tool to ablate metastatic cancer cells

Currently, there are very few therapeutic options for treatment of metastatic disease, as it often remains undetected until the burden of disease is too high. Microporous poly(ε-caprolactone) biomaterials have been shown to attract metastasizing breast cancer cells in vivo early in tumor progression. In order to enhance the therapeutic potential of these scaffolds, they were modified such that infiltrating cells could be eliminated with non-invasive focal hyperthermia. Metal disks were incorporated into poly(ε-caprolactone) scaffolds to generate heat through electromagnetic induction by an oscillating magnetic field within a radiofrequency coil. Heat generation was modulated by varying the size of the metal disk, the strength of the magnetic field (at a fixed frequency), or the type of metal. When implanted subcutaneously in mice, the modified scaffolds were biocompatible and became properly integrated with the host tissue. Optimal parameters for in vivo heating were identified through a combination of computational modeling and ex vivo characterization to both predict and verify heat transfer dynamics and cell death kinetics during inductive heating. In vivo inductive heating of implanted, tissue-laden composite scaffolds led to tissue necrosis as seen by histological analysis. The ability to thermally ablate captured cells non-invasively using biomaterial scaffolds has the potential to extend the application of focal thermal therapies to disseminated cancers.

Pulsatile Chemotherapeutic Delivery Profiles Using Magnetically Responsive Hydrogels

Pulsatile chemotherapeutic delivery profiles may provide a number advantages by maximizing the anticancer toxicity of chemotherapeutics, reducing off-target side effects, and combating adaptive resistance. While these temporally dynamic deliveries have shown some promise, they have yet to be clinically deployed from implantable hydrogels, whose localized deliveries could further enhance therapeutic outcomes. Here, several pulsatile chemotherapeutic delivery profiles were tested on melanoma cell survival in vitro and compared to constant (flatline) delivery profiles of the same integrated dose. Results indicated that pulsatile delivery profiles were more efficient at killing melanoma cells than flatline deliveries. Furthermore, results suggested that parameters like the duration of drug “on” periods (pulse width), delivery rates during those periods (pulse heights), and the number/frequency of pulses could be used to optimize delivery profiles. Optimization of pulsatile profiles at tumor sites in vivo would require hydrogel materials capable of producing a wide variety of pulsatile profiles (e.g., of different pulse heights, pulse widths, and pulse numbers). This work goes on to demonstrate that magnetically responsive, biphasic ferrogels are capable of producing pulsatile mitoxantrone delivery profiles similar to those tested in vitro. Pulse parameters such as the timing and rate of delivery during “on” periods could be remotely regulated through the use of simple, hand-held magnets. The timing of pulses was controlled simply by deciding when and for how long to magnetically stimulate. The rate of release during pulse “on” periods was a function of the magnetic stimulation frequency. These findings add to the growing evidence that pulsatile chemotherapeutic delivery profiles may be therapeutically beneficial and suggest that magnetically responsive hydrogels could provide useful tools for optimizing and clinically deploying pulsatile chemotherapeutic delivery profiles.

Direct site-specific treatment of skin cancer using doxorubicin-loaded nanofibrous membranes

Doxorubicin (DOX) is widely used in cancer therapy. However, its application is sometimes limited by its adverse cardiotoxicity and delivery pathways. In our study, we prepared a topical implantable delivery device for controlled drug release and site-specific treatment. The core region consisted of poly (lactic co-glycolic acid) and poly-caprolactone, whereas the shell region was composed of cross-linked gelatin. DOX was enclosed in the core region of a core-shell nanofiber obtained by electrospinning. This implantable delivery device was implanted on the top of the melanoma in a mouse model, which had shown a DOX-controlled release profile with sustained and sufficient local concentration against melanoma growth in mice with negligible side effects. Compared with the traditional intravenous administration, the implantable device allows precisely localized treatment and therefore can reduce the dose, decrease the injection frequency, and ensure antitumor efficacy associated with lower side effects to normal tissues. Using a coaxial electrospinning process, it is promising to deliver different hydrophobic or hydrophilic drugs for direct tumor site-specific therapy without large systemic doses and minimized systemic toxicity.

Disulfide bond based polymeric drug carriers for cancer chemotherapy and relevant redox environments in mammals

Increasing numbers of disulfide linkage-employing polymeric drug carriers that utilize the reversible peculiarity of this unique covalent bond have been reported. The reduction-sensitive disulfide bond is usually employed as a linkage between hydrophilic and hydrophobic polymers, polymers and drugs, or as cross-linkers in polymeric drug carriers. These polymeric drug carriers are designed to exploit the significant redox potential difference between the reducing intracellular environments and relatively oxidizing extracellular spaces. In addition, these drug carriers can release a considerable amount of anticancer drug in response to the reducing environment when they reach tumor tissues, effectively improving antitumor efficacy. This review focuses on various disulfide linkage-employing polymeric drug carriers. Important redox thiol pools, including GSH/GSSG, Cys/CySS, and Trx1, as well as redox environments in mammals, will be introduced.

Physicochemical and pharmacokinetic properties of polymeric films loaded with cisplatin for the treatment of malignant pleural mesothelioma

Background

Malignant mesothelioma is an invasive neoplasm arising from mesothelial surfaces of the pleural and peritoneal cavities. Mesothelioma treatment is unsatisfactory and recurrence is common. Here an innovative locoregional treatment for malignant pleural mesothelioma is presented.

Methods

Chitosan- and hyaluronate-based films were loaded with 0.5% and 4% w/w cisplatin and were studied for their physicochemical, mechanical and drug release characteristics. The performance of the drug delivery systems was assessed in vitro on A549 cells and on an orthotopic model of MPM recurrence in rats.

Results

Polysaccharide films produced were thin, flexible and resistant. Cisplatin was completely released from hyaluronic acid films within 96 hours, while drug release was found to be much more prolonged with chitosan films. The drug released from hyaluronate films was effective against A549 cell line, while for chitosan films the release was too slow to produce cytotoxicity. Similarly, cisplatin-loaded chitosan films in vivo released minimal quantities of cisplatin and induced inflammation and foreign body reaction. Cisplatin-loaded hyaluronate acid films on the contrary were able to prevent tumor recurrence. The cisplatin-loaded hyaluronate films provided higher C_max and AUC compared to a solution of cisplatin administered intrapleurally, but did not show any sign of treatment related toxicity.

Conclusions

Hyaluronate-based films appear as an optimal platform for the development of drug delivery systems suitable for the loco-regional post-surgical treatment of lung malignancies.

Characterization and antitumor efficacy of poly(L-lactid acid)-based etoposide-loaded implants

Etoposide is widely used in the chemotherapy of a variety of malignancies. But the strong lipophilicity, poor bioavailability, and severe side effects of etoposide limit its clinical application. The aim of this study was to develop sustained-release etoposide-loaded implants and evaluate antitumor activity of the implants after intratumoral implantation. We prepared the implants containing etoposide, poly(L-lactid acid) and polyethylene glycol 4000 by the direct compression method. The implants were characterized regarding drug-excipient compatibility, content uniformity, morphology, sterility, in vitro, and in vivo release profiles. Then the antitumor activity of the implants was tested in xenograft model of A549 human non-small cell lung cancer. SEM images displayed smooth surface of the implant and indicated that etoposide was homogeneously dispersed in the polymeric matrix. The results of content uniformity met the requirements of the Chinese Pharmacopoeia. Both in vitro and in vivo release profiles of the implants were characterized by high burst release followed by sustained release of etoposide. Intratumoral implantation of etoposide-loaded implants could efficiently delay the tumor growth. Furthermore, increasing the dose of implants led to higher tumor suppression rate without adding systemic toxicity. These results indicated that etoposide-loaded implants have significant antitumor efficacy in xenograft model without dose-limiting side effects and they possess a strong potential to be used as an intratumoral chemotherapy option for lung cancer treatment.

Enhanced antitumor efficacy of poly(D,L-lactide-co-glycolide)-based methotrexate-loaded implants on sarcoma 180 tumor-bearing mice

Purpose

Methotrexate is widely used in chemotherapy for a variety of malignancies. However, severe toxicity, poor pharmacokinetics, and narrow safety margin of methotrexate limit its clinical application. The aim of this study was to develop sustained-release methotrexate-loaded implants and evaluate antitumor activity of the implants after intratumoral implantation.

Materials and methods

We prepared the implants containing methotrexate, poly(D,L-lactide-co-glycolide), and polyethylene glycol 4000 with the melt-molding technique. The implants were characterized with regards to drug content, morphology, in vitro, and in vivo release profiles. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were carried out to investigate the physicochemical properties of the implants. Furthermore, the antitumor activity of the implants was tested in a sarcoma 180 mouse model.

Results

The implants were prepared as solid rods. Scanning electron microscopy images showed a smooth surface of the implant, suggesting that methotrexate was homogeneously dispersed in the polymeric matrix. The results of DSC and FTIR indicated that no significant interaction between methotrexate and the polymer was observed in the implants. Both in vitro and in vivo release profiles of the implants were characterized by burst release followed by sustained release of methotrexate. Intratumoral implantation of methotrexate-loaded implants could efficiently delay tumor growth. Moreover, an increase in the dose of implants led to a higher tumor suppression rate without additional systemic toxicity.

Conclusion

These results demonstrate that methotrexate-loaded implants had significant antitumor efficacy in a sarcoma 180 mouse model without dose-limiting side effects, and suggest that the implants could be potentially applied as an intratumoral delivery system to treat cancer.

Use of a Novel Polymer in an Animal Model of Head and Neck Squamous Cell Carcinoma

Objective To evaluate the adverse effects and therapeutic efficacy of our biocompatible polymer platform delivering targeted local therapy of cytokine CCL21 and cisplatin in a partially resected xenograft animal model of head and neck squamous cell carcinoma. In addition, to evaluate the efficacy of cotreatment with radiotherapy and assess the biocompatibility of the cisplatin-eluting polymer in the murine neck. Study Design Experimental animal study. Setting Academic research laboratory. Subjects and Methods SCCVII/SF cell injection established head and neck squamous cell carcinoma tumors in C3H/HeJ mice. Subjects underwent surgery, and a chemokine-eluting polymer was implanted into the resected site. Subjects treated with cisplatin received radiation or no radiation, and tissue was harvested after 8 weeks to assess polymer biocompatibility. Results Our results with the polymer platform significantly ( P < .05) reduced SCCVII/SF tumor size in C3H/HeJ mice with cisplatin (49% ± 8.7%, Δ3.4 ± 0.6 cm³ [95% CI]), CCL21 (42% ± 4.8%, Δ3.5 ± 0.4 cm³), and cisplatin/CCL21 dual-agent polymer (82% ± 4.4%, Δ8.0 ± 0.4 cm³) as compared with controls. Cisplatin polymer with high-dose (16 Gy) and low-dose (4 Gy) radiation reduced tumor mass (respectively, 92% ± 7.2%, Δ6.1 ± 0.5 cm³; 85% ± 7.4%, Δ5.7 ± 0.5 cm³) as compared with the reduction from high-dose radiotherapy alone (70% ± 7.9%, Δ4.7 ± 0.5 cm³). No significant toxicity or inflammation was noted on histopathology after radiotherapy and cisplatin-eluting polymer treatment. Conclusion Cisplatin, CCL21, and cisplatin/CCL21 dual-agent polymer all exhibit significant antitumor effects and decrease tumor burden. Moreover, combination cisplatin polymer with radiotherapy may permit a decrease in intensity of radiation therapy in patients having received the cisplatin polymer. Histopathologic analysis suggests that the polymer is free from significant adverse effects in this model and warrants clinical trial.

pH responsive cross-linked polymeric matrices based on natural polymers: effect of process variables on swelling characterization and drug delivery properties

Introduction: The current work was aimed to design and synthesize novel crosslinked pH-sensitive gelatin/pectin (Ge/Pec) hydrogels using different polymeric ratios and to explore the effect of polymers and degree of crosslinking on dynamic, equilibrium swelling and in vitro release behavior of the model drug (Mannitol). Methods: The Ge/Pec based hydrogels were prepared using glutaraldehyde as the crosslinker. Various structural parameters that affect their release behavior were determined, including swelling study, porosity, sol-gel analysis, average molecular weight between crosslinks (Mc), volume fraction of polymer (V2,s), solvent interaction parameter (χ) and diffusion coefficient. The synthesized hydrogels were subjected to various characterization tools like Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and DSC differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Results: The hydrogels show highest water uptake and release at lower pH values. The FTIR spectra showed an interaction between Ge and Pec, and the drug-loaded samples also showed the drug-related peaks, indicating proper loading of the drug. DSC and TGA studies confirmed the thermal stability of hydrogel samples, while SEM showed the porous nature of hydrogels. The drug release followed non-Fickian diffusion or anomalous mechanism. Conclusion: Aforementioned characterizations reveal the successful formation of copolymer hydrogels. The pH-sensitive swelling ability and drug release behavior suggest that the rate of polymer chain relaxation and drug diffusion from these hydrogels are comparable which also predicts their possible use for site-specific drug delivery.

Molecularly imprinted cryogel membranes for mitomycin C delivery

In this study, cryogel-based implantable molecularly imprinted drug delivery systems were designed for the delivery of antineoplastic agent. Mitomycin C imprinted poly(2-hydroxyethyl methacrylate-N-methacryloyl-l-glutamic acid) cryogel membranes were produced by free-radical bulk polymerization under partially frozen conditions. The membranes were characterized by swelling tests, Fourier transform infrared spectroscopy, scanning electron microscopy, surface area measurements and in vitro hemocompatibility tests. In vitro delivery studies were carried out to examine the effects of cross-linker ratio and template content. Mitomycin C imprinted cryogel membranes have megaporous structure (10-100 μm in diameter). The cumulative release of mitomycin C was decreased with increasing cross-linking agent ratio and increased with the amount of template in the cryogel structure. The nature of transport mechanism of the mitomycin C from the membranes was non-Fickian.

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.

Ultrasound-guided intratumoral delivery of doxorubicin from in situ forming implants in a hepatocellular carcinoma model

BACKGROUND

Hepatocellular carcinomas are frequently nonresponsive to systemically delivered drugs. Local delivery provides an alternative to systemic administration, maximizing the dose delivered to the tumor, achieving sustained elevated concentrations of the drug, while minimizing systemic exposure.

RESULTS

Ultrasound-guided deposition of doxorubicin (Dox)-eluting in situ forming implants (ISFI) in an orthotopic tumor model significantly lowers systemic drug levels. As much as 60 µg Dox/g tumors were observed 21 days after ISFI injection. Tumors treated with Dox implants also showed a considerable reduction in progression at 21 days.

CONCLUSION

Dox-eluting ISFIs provide a promising platform for the treatment of hepatocellular carcinomas by which drug can be delivered directly into the lesion, bypassing distribution and elimination by the circulatory system.

Development and evaluation of natural gum-based extended release matrix tablets of two model drugs of different water solubilities by direct compression

The study was aimed at developing extended release matrix tablets of poorly water-soluble diclofenac sodium and highly water-soluble metformin hydrochloride by direct compression using cashew gum, xanthan gum and hydroxypropylmethylcellulose (HPMC) as release retardants. The suitability of light grade cashew gum as a direct compression excipient was studied using the SeDeM Diagram Expert System. Thirteen tablet formulations of diclofenac sodium (∼100 mg) and metformin hydrochloride (∼200 mg) were prepared with varying amounts of cashew gum, xanthan gum and HPMC by direct compression. The flow properties of blended powders and the uniformity of weight, crushing strength, friability, swelling index and drug content of compressed tablets were determined. In vitro drug release studies of the matrix tablets were conducted in phosphate buffer (diclofenac: pH 7.4; metformin: pH 6.8) and the kinetics of drug release was determined by fitting the release data to five kinetic models. Cashew gum was found to be suitable for direct compression, having a good compressibility index (ICG) value of 5.173. The diclofenac and metformin matrix tablets produced generally possessed fairly good physical properties. Tablet swelling and drug release in aqueous medium were dependent on the type and amount of release retarding polymer and the solubility of drug used. Extended release of diclofenac (∼24 h) and metformin (∼8-12 h) from the matrix tablets in aqueous medium was achieved using various blends of the polymers. Drug release from diclofenac tablets fitted zero order, first order or Higuchi model while release from metformin tablets followed Higuchi or Hixson-Crowell model. The mechanism of release of the two drugs was mostly through Fickian diffusion and anomalous non-Fickian diffusion. The study has demonstrated the potential of blended hydrophilic polymers in the design and optimization of extended release matrix tablets for soluble and poorly soluble drugs by direct compression.

Poly(ester-anhydride) for controlled delivery of hydrophilic drugs

Injectable pasty polyester-anhydride based on sebacic acid and ricinoleic acid at a 30:70 w/w ratio, poly(sebacic-co-ricinoleic-ester-anhydride) 3:7, was synthesized from the esterification of ricinoleic acid on poly(sebacic acid) followed by polyanhydride condensation. The effect of castor oil, citric acid, and glycerol added at 1% w/w as branching agents was determined. Castor oil and citric acid increased the viscosity, while glycerol decreased the viscosity of the polymer. Constant release of gentamicin and thyrotropin-releasing hormone incorporated in the polymer paste was monitored during 28 days.

Reduction-sensitive polymeric nanocarriers in cancer therapy: a comprehensive review

Redox potential is regarded as a significant signal to distinguish between the extra-cellular and intra-cellular environments, as well as between tumor and normal tissues. Taking advantage of this physiological differentiation, various reduction-sensitive polymeric nanocarriers (RSPNs) have been designed and explored to demonstrate excellent stability during blood circulation but rapidly degrade and effectively trigger drug release in tumor cells. Therefore, this smart RSPN delivery system has attracted much attention in recent years, as it represents one of the most promising drug delivery strategies in cancer therapy. In this review, we will provide a comprehensive overview of RSPNs with various reducible linkages and functional groups up to date, including their design and synthetic strategies, preparation methods, drug release behavior, and their in vitro and in vivo efficacy in cancer therapy. In addition, dual- and triple-sensitive nanocarriers based on reducible disulfide bond-containing linkages will also be discussed.