Fine tuning of the pH-dependent drug release rate from polyHPMA-ellipticinium conjugates

Keratinocyte membrane-mediated nanodelivery system with dissolving microneedles for targeted therapy of skin diseases

There is a lack of actively targeting drug delivery carriers for the topical treatment of epidermal diseases, which results in drug waste and an increased incidence of toxic side effects in the clinic. We recently discovered that epidermal cells (HaCaT cells) have homologous targeting functions and developed HaCaT cell membrane-coated pH-sensitive micelles for therapeutic active targeting of skin disease. We encapsulated shikonin in these biomimetic nanocarriers and found that the nanocarriers accumulated mainly in the active epidermis when delivered with karaya gum-fabricated water-soluble microneedles. The nanocarriers were internalized by the target cells, resulting in swelling of histidine fragments with protonation and subsequent triggering of drug release, which increased the therapeutic efficacy of shikonin against imiquimod-induced psoriatic epidermal hyperplasia. This emerging biomimetic delivery strategy is a new approach for improving the treatment of skin diseases and is also very promising for use in the field of cosmetics. Additionally, we found abnormally high protein expression of Na⁺/K⁺-ATPase in diseased skin; thus, this protein may be a biomarker of psoriasis.

Poly(2-methyl-2-oxazoline) conjugates with doxorubicin: From synthesis of high drug loading water-soluble constructs to in vitro anti-cancer properties

Poly(2-oxazoline)s represent an emerging class of polymers with increasing potential in biomedical sciences. To date, most of the work on poly(2-oxazoline)-drug conjugates focused on poly(2-ethyl-2-oxazoline) (PEtOx), a biocompatible water-soluble polymer with biological properties similar to polyethylene glycol. However, the more hydrophilic poly(2-methyl-2-oxazoline) (PMeOx) shows better anti-fouling properties than PEtOx and thus indicates greater potential for the construction of polymer therapeutics. Herein, we synthesized for the first time a drug delivery system based on a linear PMeOx with a molar mass that is high enough (40 kDa) to exploit passive accumulation in the tumor by the enhanced permeation and retention effect. The anti-cancer drug doxorubicin is attached to the polymer carrier via an acid-sensitive hydrazone bond, which allows its pH-triggered release in the tumor. The in vitro study demonstrates successful cellular uptake of the PMeOx-doxorubicin conjugate via clathrin-mediated endocytosis, pH-sensitive drug release and high cytotoxicity against B16 melanoma cells. Finally, these properties were critically compared to the analogous systems based on the established PEtOx revealing that the more hydrophilic PMeOx carrier outperforms PEtOx in most of the parameters, showing higher maximal drug loading, superior cellular uptake, better anti-fouling properties, as well as improved in vitro anti-cancer efficiency. The study demonstrates the potential of PMeOx as a versatile platform for synthesis of new drug delivery systems.

Designing Smart Polymer Conjugates for Controlled Release of Payloads

Incorporating labile bonds inside polymer backbone and side chains yields interesting polymer materials that are responsive to change of environmental stimuli. Drugs can be conjugated to various polymers through different conjugation linkages and spacers. One of the key factors influencing the release profile of conjugated drugs is the hydrolytic stability of the conjugated linkage. Generally, the hydrolysis of acid-labile linkages, including acetal, imine, hydrazone, and to some extent β-thiopropionate, are relatively fast and the conjugated drug can be completely released in the range of several hours to a few days. The cleavage of ester linkages are usually slow, which is beneficial for continuous and prolonged release. Another key structural factor is the water solubility of polymer-drug conjugates. Generally, the release rate from highly water-soluble prodrugs is fast. In prodrugs with large hydrophobic segments, the hydrophobic drugs are usually located in the hydrophobic core of micelles and nanoparticles, which limits the access to the water, hence lowering significantly the hydrolysis rate. Finally, self-immolative polymers are also an intriguing new class of materials. New synthetic pathways are needed to overcome the fact that much of the small molecules produced upon degradation are not active molecules useful for biomedical applications.

Release behavior of VAN from four types of CaP-ceramic granules using various loading methods at two different degrees of acidity

The release behavior of vancomycin (VAN) from beta-tricalciumphosphate (βTCP), hydroxyapatite (HA), glass ceramic (GC) and sponge-like collagen βTCP granule composite (sponge) was studied. Vacuum and drip loading methods were compared. The influence of VAN concentration and pH on release behavior was analyzed with respect to a stable release level of VAN above the minimum inhibitory concentration over 14 days. Initially the morphology of the granule carrier systems was examined with ESEM, stereomicroscopy, µCT-imaging and Camsizer® regarding porosity, interconnecting pores and granule size. Drug release patterns following a vacuum and a drip loading method with VAN at concentrations of 5 and 50 mg/ml were compared. The influence of pH 7.4 compared to pH 5.0 on release behavior was studied. The drug was released in bidistilled water at 37 °C, the concentration determined by photometry at 220 nm. For statistical purposes, the mean and standard deviation were calculated and analyzed by Origin 9.1 Professional SR1 (OriginLab). Due to low interconnectivity and low porosity, the vacuum loading method was unable to attain complete drug loading of the ceramic granules. The sponge showed an inhomogeneous distribution of βTCP granules. Drug release was high at pH 7.4, at pH 5.0 it practically did not occur. All samples except for the collagen-complex show an initial VAN burst release with a following steady release. Loading with 5 mg/ml concentrated VAN resulted in a higher percentage of available drug being released. However, when loaded with 50 mg/ml, the absolute amount of drug released was higher.

Poly(2-ethyl-2-oxazoline) conjugates with doxorubicin for cancer therapy: In vitro and in vivo evaluation and direct comparison to poly[N-(2-hydroxypropyl)methacrylamide] analogues

We designed and synthesized a new delivery system for the anticancer drug doxorubicin based on a biocompatible hydrophilic poly(2-ethyl-2-oxazoline) (PEtOx) carrier with linear architecture and narrow molar mass distribution. The drug is connected to the polymer backbone via an acid-sensitive hydrazone linker, which allows its triggered release in the tumor. The in vitro studies demonstrate successful cellular uptake of conjugates followed by release of the cytostatic cargo. In vivo experiments in EL4 lymphoma bearing mice revealed prolonged blood circulation, increased tumor accumulation and enhanced antitumor efficacy of the PEtOx conjugate having higher molecular weight (40 kDa) compared to the lower molecular weight (20 kDa) polymer. Finally, the in vitro and in vivo anti-cancer properties of the prepared PEtOx conjugates were critically compared with those of the analogous system based on the well-established PHPMA carrier. Despite the relatively slower intracellular uptake of PEtOx conjugates, resulting also in their lower cytotoxicity, there are no substantial differences in in vivo biodistribution and anti-cancer efficacy of both classes of polymer-Dox conjugates. Considering the synthetic advantages of poly(2-alkyl-2-oxazoline)s, the presented study demonstrates their potential as a versatile alternative to well-known PEO- or PHPMA-based materials for construction of drug delivery systems.

HPMA Copolymer-Drug Conjugates with Controlled Tumor-Specific Drug Release

Over the past few decades, numerous polymer drug carrier systems are designed and synthesized, and their properties are evaluated. Many of these systems are based on water-soluble polymer carriers of low-molecular-weight drugs and compounds, e.g., cytostatic agents, anti-inflammatory drugs, or multidrug resistance inhibitors, all covalently bound to a carrier by a biodegradable spacer that enables controlled release of the active molecule to achieve the desired pharmacological effect. Among others, the synthetic polymer carriers based on N-(2-hydroxypropyl) methacrylamide (HPMA) copolymers are some of the most promising carriers for this purpose. This review focuses on advances in the development of HPMA copolymer carriers and their conjugates with anticancer drugs, with triggered drug activation in tumor tissue and especially in tumor cells. Specifically, this review highlights the improvements in polymer drug carrier design with respect to the structure of a spacer to influence controlled drug release and activation, and its impact on the drug pharmacokinetics, enhanced tumor uptake, cellular trafficking, and in vivo antitumor activity.

Radiolabelled Polymeric Materials for Imaging and Treatment of Cancer: Quo Vadis?

Owing to their tunable blood circulation time and suitable plasma stability, polymer-based nanomaterials hold a great potential for designing and utilising multifunctional nanocarriers for efficient imaging and effective treatment of cancer. When tagged with appropriate radionuclides, they may allow for specific detection (diagnosis) as well as the destruction of tumours (therapy) or even customization of materials, aiming to both diagnosis and therapy (theranostic approach). This review provides an overview of recent developments of radiolabelled polymeric nanomaterials (natural and synthetic polymers) for molecular imaging of cancer, specifically, applying nuclear techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT). Different approaches to radiolabel polymers are evaluated from the methodical radiochemical point of view. This includes new bifunctional chelating agents (BFCAs) for radiometals as well as novel labelling methods. Special emphasis is given to eligible strategies employed to evade the mononuclear phagocytic system (MPS) in view of efficient targeting. The discussion encompasses promising strategies currently employed as well as emerging possibilities in radionuclide-based cancer therapy. Key issues involved in the clinical translation of radiolabelled polymers and future scopes of this intriguing research field are also discussed.

Seven years of radionuclide laboratory at IMC - important achievements

For many important research topics in polymer science the use of radionuclides brings significant benefits concerning nanotechnology, polymer drug delivery systems, tissue engineering etc. This contribution describes important achievements of the radionuclide laboratory at Institute of Macromolecular Chemistry of the Academy of Sciences of the Czech Republic (IMC) in the area of polymers for biomedical applications. Particular emphasis will be given to water-soluble polymer carriers of radionuclides, thermoresponsive polymer radionuclide carriers, thermoresponsive polymers for local brachytherapy, polymer scaffolds modified with (radiolabeled) peptides and polymer copper chelators for the therapy of Wilson´s disease.

Formation of DNA adducts by ellipticine and its micellar form in rats - a comparative study

The requirements for early diagnostics as well as effective treatment of cancer diseases have increased the pressure on development of efficient methods for targeted drug delivery as well as imaging of the treatment success. One of the most recent approaches covering the drug delivery aspects is benefitting from the unique properties of nanomaterials. Ellipticine and its derivatives are efficient anticancer compounds that function through multiple mechanisms. Formation of covalent DNA adducts after ellipticine enzymatic activation is one of the most important mechanisms of its pharmacological action. In this study, we investigated whether ellipticine might be released from its micellar (encapsulated) form to generate covalent adducts analogous to those formed by free ellipticine. The ³²P-postlabeling technique was used as a useful imaging method to detect and quantify covalent ellipticine-derived DNA adducts. We compared the efficiencies of free ellipticine and its micellar form (the poly(ethylene oxide)-block-poly(allyl glycidyl ether) (PAGE-PEO) block copolymer, P 119 nanoparticles) to form ellipticine-DNA adducts in rats in vivo. Here, we demonstrate for the first time that treatment of rats with ellipticine in micelles resulted in formation of ellipticine-derived DNA adducts in vivo and suggest that a gradual release of ellipticine from its micellar form might produce the enhanced permeation and retention effect of this ellipticine-micellar delivery system.