Richard Laga

The therapeutic efficacy of antitumor nanomedicines is influenced by numerous factors, with the most critical being the selection of an appropriate biomaterial and the use of suitable stimulus-responsive linkers. The chosen biomaterial must be biocompatible and capable of binding the drug via a linker that facilitates selective release and activation of the therapeutic effect, specifically within tumor tissue. In this study, we designed, synthesized, and compared the physicochemical and biological properties of various polymer nanomedicines, each bearing pirarubicin conjugated to water-soluble and biocompatible methacrylamide-based copolymers through pH-sensitive hydrazone bonds. Our findings indicate that the hydrophobicity and length of the linker near the hydrazone bond are crucial factors influencing the treatment efficacy of the nanomedicines. Conjugates with aminohexanoyl linkers exhibited superior drug release and enhanced antitumor activity compared with those with shorter linkers. Overall, our study highlights that the rate of drug release, governed by the linker structure, plays a pivotal role in therapeutic efficacy, while the hydrophilicity of the polymer backbone has a lesser impact.

The demand for high-resolution imaging of nanomaterials continues to grow across disciplines. However, conventional support films for transmission and scanning transmission electron microscopy (TEM/STEM) are often limited by low beam resistance, suboptimal resolution, toxicity concerns, and high production costs. This study introduces a new application of a self-supporting, biocompatible thin film composed of hydrophilic, crosslinked poly[N-(2-hydroxypropyl)methacrylamide] (p(HPMA)) as an alternative to traditional carbon or organic polymer supports. The film forms a stable, continuous interfacial layer that promotes homogeneous nanoparticle dispersion and minimizes aggregation, critical factors for accurate analysis of nanoscale interfacial interactions. By embedding nanoparticles within the hydrated polymer matrix, the film provides a consistent and reproducible interface, enabling detailed observation of particle behavior, stability, and interactions at both solid-liquid and solid-vacuum boundaries. Resolution measurements show improvements of up to 38% over Formvar and 33% over graphene oxide. Film thicknesses range from 3.5 to 22.9 nm, spanning the holes in Lacey and Quantifoil grids. The film is produced using a rapid, scalable casting method using standard laboratory materials. TEM and STEM imaging confirm its structural and beam stability under accelerating voltages up to 200 kV. Nanoparticle dispersion and film integrity are preserved for at least six months. These findings highlight the potential of this polymer-based support film as a cost-effective and sustainable platform for high-resolution electron microscopy, with broad relevance to colloid and interface science, nanomedicine, and environmental nanotechnology.

To tackle the main challenges in gene therapy, synthetic polycationic vectors are developed for nucleic acid (NA) delivery. In this work, vectors based on di‐block copolymers consisting of a methacrylate‐type cationic block and an electroneutral hydrophilic block are designed and synthesized to condense NA into compact particles shielded with a bioinert hydrophilic polymer layer. The results confirm that the cationic vector blocks, containing permanently charged trimethylammonium (TMA) or tributylphosphonium (TBP) groups and 0–20 mol% hydrophobic butyl groups, are able to efficiently complex DNA to form 100 to 200 nm spheroids, while the hydrophilic blocks based on 2‐methacryloyloxyethylphosphorylcholine or N‐(2‐hydroxypropyl) methacrylamide coat the nanoparticle surfaces with an electroneutral polymer layer. Additionally, pH‐responsive hydrazone bonds are incorporated between the TMA and TBP groups and the main polymer backbone of the polycationic block to ensure hydrolysis of the hydrazone bond. Theoretically, this should be accompanied by DNA release from the complex in a mildly acidic environment inside the cells while maintaining its stability under neutral blood conditions. In summary, this model study provides insight into the process of complexation/decomplexation of NA by pH‐responsive di‐block polycationic vectors. The results may contribute to the development of safe and efficient delivery systems for gene therapy applications.

The development of stimuli-responsive drug delivery systems enables targeted delivery and environment-controlled drug release, thereby minimizing off-target effects and systemic toxicity. We prepared and studied tailor-made dual-responsive systems (thermo- and pH-) based on synthetic diblock copolymers consisting of a fully hydrophilic block of poly[N-(1,3-dihydroxypropyl)methacrylamide] (poly(DHPMA)) and a thermoresponsive block of poly[N-(2,2-dimethyl-1,3-dioxan-5-yl)methacrylamide] (poly(DHPMA-acetal)) as drug delivery and smart stimuli-responsive materials. The copolymers were designed for eventual medical application to be fully soluble in aqueous solutions at 25 °C. However, they form well-defined nanoparticles with hydrodynamic diameters of 50-800 nm when heated above the transition temperature of 27-31 °C. This temperature range is carefully tailored to align with the human body's physiological conditions. The formation of the nanoparticles and their subsequent decomposition was studied using dynamic light scattering (DLS), transmission electron microscopy (TEM), isothermal titration calorimetry (ITC), and nuclear magnetic resonance (NMR). ¹H NMR studies confirmed that after approximately 20 h of incubation at pH 5, which closely mimics tumor microenvironment, approximately 40% of the acetal groups were hydrolyzed, and the thermoresponsive behavior of the copolymers was lost. This smart polymer response led to disintegration of the supramolecular structures, possibly releasing the therapeutic cargo. By tuning the transition temperature to the values relevant for medical applications, we ensure precise and effective drug release. In addition, our systems did not exhibit any cytotoxicity against any of the three cell lines. Our findings underscore the immense potential of these nanoparticles as eventual advanced drug delivery systems, especially for cancer therapy.

Poly(2‐( N , N ‐dimethylamino)ethyl acrylate) (PDMAEA) is a promising charge‐shifting polycation with the capacity to form a range of morphologically distinct polyelectrolyte assemblies. Nevertheless, the basic character of the monomer and its hydrolytic instability impedes its controlled synthesis to higher molecular weight (MW). Herein, the reversible addition‐fragmentation chain transfer polymerization of DMAEA is reported using a tert‐butanol/V70 initiator/trithiocarbonate‐based chain transfer agent (CTA) polymerization setup. The CTA instability is demonstrated in the presence of the unprotonated tertiary amino group of the DMAEA monomer, which limits the control over the conversion and MW of the polymer. In contrast, the shielding of the amino groups by their protonation leads to polymerization with high conversions and excellent control over MWs of polymer up to 100 000 g mol ⁻¹ . Hydrolytic degradation study at pH values ranging from 5 to 9 reveals that both basic and protonated PDMAEA undergo a pH‐dependent hydrolysis. The proposed polymerization conditions provide a means of synthesizing PDMAEA with well‐controlled characteristics, which are beneficial for controlling the complexation processes during the formation of various polyelectrolyte assemblies.

Minimal immunogen vaccines are being developed to focus antibody responses against otherwise challenging targets, including human immunodeficiency virus (HIV), but multimerization of the minimal peptide immunogen on a carrier platform is required for activity. Star copolymers comprising multiple hydrophilic polymer chains ("arms") radiating from a central dendrimer unit ("core") were recently reported to be an effective platform for arraying minimal immunogens for inducing antibody responses in mice and primates. However, the impact of different parameters of the star copolymer (e.g., minimal immunogen density and hydrodynamic size) on antibody responses and the optimal synthetic route for controlling those parameters remains to be fully explored. We synthesized a library of star copolymers composed of poly[N-(2-hydroxypropyl)methacrylamide] hydrophilic arms extending from poly(amidoamine) dendrimer cores with the aim of identifying the optimal composition for use as minimal immunogen vaccines. Our results show that the length of the polymer arms has a crucial impact on the star copolymer hydrodynamic size and is precisely tunable over a range of 20-50 nm diameter, while the dendrimer generation affects the maximum number of arms (and therefore minimal immunogens) that can be attached to the surface of the dendrimer. In addition, high-resolution images of selected star copolymer taken by a custom-modified environmental scanning electron microscope enabled the acquisition of high-resolution images, providing new insights into the star copolymer structure. Finally, in vivo studies assessing a star copolymer vaccine comprising an HIV minimal immunogen showed the criticality of polymer arm length in promoting antibody responses and highlighting the importance of composition tunability to yield the desired biological effect.

In this work, we present the synthesis and evaluation of magnetic resonance (MR) properties of novel phosphorus/iron-containing probes for dual ³¹P and ¹H MR imaging and spectroscopy (MRI and MRS). The presented probes are composed of biocompatible semitelechelic and multivalent phospho-polymers based on poly(2-methacryloyloxyethyl phosphorylcholine) (pMPC) coordinated with small paramagnetic Fe³⁺ ions or superparamagnetic maghemite (γ-Fe₂O₃) nanoparticles via deferoxamine group linked to the end or along the polymer chains. All probes provided very short ¹H T₁ and T₂ relaxation times even at low iron concentrations. The presence of iron had a significant impact on the shortening of ³¹P relaxation, with the effect being more pronounced for probes based on γ-Fe₂O₃ and multivalent polymer. While the water-soluble probe having one Fe³⁺ ion per polymer chain was satisfactorily visualized by both ³¹P-MRS and ³¹P-MRI, the probe with multiple Fe³⁺ ions could only be detected by ³¹P-MRS, and the probes consisting of γ-Fe₂O₃ nanoparticles could not be imaged by either technique due to their ultra-short ³¹P relaxations. In this proof-of-principle study performed on phantoms at a clinically relevant magnetic fields, we demonstrated how the different forms and concentrations of iron affect both the ¹H MR signal of the surrounding water molecules and the ³¹P MR signal of the phospho-polymer probe. Thus, this double contrast can be exploited to simultaneously visualize body anatomy and monitor probe biodistribution.