This review provides a summary of recent progress in the development of different nano-platforms for the efficient synergistic effect between photodynamic therapy and chemotherapy. In particular, this review focuses on various methods in which photosensitizers and chemotherapeutic agents are co-delivered to the targeted tumor site. In many cases, the photosensitizers act as drug carriers, but this review, also covers different types of appropriate nanocarriers that aid in the delivery of photosensitizers to the tumor site. These nanocarriers include transition metal, silica and graphene-based materials, liposomes, dendrimers, polymers, metal–organic frameworks, nano emulsions, and biologically derived nanocarriers. Many studies have demonstrated various benefits from using these nanocarriers including enhanced water solubility, stability, longer circulation times, and higher accumulation of therapeutic agents/photosensitizers at tumor sites. This review also describes novel approaches from different research groups that utilize various targeting strategies to increase treatment efficacy through simultaneous photodynamic therapy and chemotherapy.

Conductive and biofriendly gold nanomaterial inks are highly desirable for printed electronics, biosensors, wearable electronics, and electrochemical sensor applications. Here, we demonstrate the scalable synthesis of stable gold nanoparticle inks with low-temperature sintering using simple chemical processing steps. Multiprinter compatible aqueous gold nanomaterial inks were formulated, achieving resistivity as low as ∼10^-6 Ω m for 400 nm thick films sintered at 250 °C. Printed lines with a resolution of <20 μm and minimal overspray were obtained using an aerosol jet printer. The resistivity of the printed patterns reached ∼9.59 ± 1.2 × 10^-8 Ω m after sintering at 400 °C for 45 min. Our aqueous-formulated gold nanomaterial inks are also compatible with inkjet printing, extending the design space and manufacturability of printed and flexible electronics where metal work functions and chemically inert films are important for device applications.

ZnO nanoparticles (nZnO) are commonly used in nanotechnology applications despite their demonstrated cytotoxicity against multiple cell types. This underscores the significant need to determine the physicochemical properties that influence nZnO cytotoxicity. In this study, we analyzed six similarly sized nZnO formulations, along with SiO₂-coated nZnO, bulk ZnO and ZnSO₄ as controls. Four of the nZnO samples were synthesized using various wet chemical methods, while three employed high-temperature flame spray pyrolysis (FSP) techniques. X-ray diffraction and optical analysis demonstrated the lattice parameters and electron band gap of the seven nZnO formulations were similar. However, zeta potential measures, hydrodynamic size, photocatalytic rate constants, dissolution potential, reactive oxygen species (ROS) production and, more importantly, the cytotoxicity of the variously synthesized nZnO towards Jurkat leukemic and primary CD4⁺ T cells displayed major differences. Surface structure analysis using FTIR, X-ray photoelectron spectroscopies (XPS) and dynamic light scattering (DLS) revealed significant differences in the surface-bound chemical groups and the agglomeration tendencies of the samples. The wet chemical nZnO, with higher cationic surface charge, faster photocatalytic rates, increased extracellular dissolution and ROS generation demonstrated greater cytotoxicity towards both cell types than those made with FSP techniques. Furthermore, principal component analysis (PCA) suggests that the synthesis procedure employed influences which physicochemical properties contribute more to the cytotoxic response. These results suggest that the synthesis approach results in unique surface chemistries and can be a determinant of cellular cytotoxicity and oxidative stress responses.

Three-dimensional (3D) tissue engineering (TE) is a prospective treatment that can be used to restore or replace damaged musculoskeletal tissues, such as articular cartilage. However, current challenges in TE include identifying materials that are biocompatible and have properties that closely match the mechanical properties and cellular microenvironment of the target tissue. Visualization and analysis of potential 3D porous scaffolds as well as the associated cell growth and proliferation characteristics present additional problems. This is particularly challenging for opaque scaffolds using standard optical imaging techniques. Here, we use graphene foam (GF) as a 3D porous biocompatible substrate, which is scalable, reproducible, and a suitable environment for ATDC5 cell growth and chondrogenic differentiation. ATDC5 cells are cultured, maintained, and stained with a combination of fluorophores and gold nanoparticles to enable correlative microscopic characterization techniques, which elucidate the effect of GF properties on cell behavior in a 3D environment. Most importantly, the staining protocol allows for direct imaging of cell growth and proliferation on opaque scaffolds using X-ray MicroCT, including imaging growth of cells within the hollow GF branches, which is not possible with standard fluorescence and electron microscopy techniques.

In this work, we report on the effects of doping SnO₂ nanoparticles with Zn²⁺ ions. A series of ∼2–3 nm sized Sn_1−xZn_xO₂ crystallite samples with 0 ≤ x ≤ 0.18 were synthesized using a forced hydrolysis method. Increasing dopant concentration caused systematic changes in the crystallite size, oxidation state of Sn, visible emission, and band gap of SnO₂ nanoparticles. X-ray Diffraction studies confirmed the SnO₂ phase purity and the absence of any impurity phases. Magnetic measurements at room temperature showed a weak ferromagnetic behavior characterized by an open hysteresis loop. Their saturation magnetization M_s increases initially with increasing Zn concentrations; however for x > 0.06, M_s decreases. Samples with the highest M_s values (x = 0.06) were analyzed using an Inductively Coupled Plasma Mass Spectrometer, looking for traces of any magnetic elements in the samples. Concentrations of all transition metals (Fe, Co, Mn, Cr, and Ni) in these samples were below ppb level, suggesting that the observed magnetism is not due to random inclusions of any spurious magnetic impurities and it cannot be explained by the existing models of magnetic exchange. A new visible emission near 490 nm appeared in the Zn doped SnO₂ samples in the photoluminescence spectra which strengthened as x increased, suggesting the formation of defects such as oxygen vacancies. X-ray Photoelectron Spectroscopy (XPS) confirmed the nominal Zn dopant concentrations and the 2+ oxidation state of Zn in the Sn_1−xZn_xO₂ samples. Interestingly, the XPS data indicated the presence of a small fraction of Sn²⁺ ions in Sn_1−xZn_xO₂ samples in addition to the expected Sn⁴⁺, and the Sn²⁺ concentration increased with increasing x. The presence of multi-valent metal ions and oxygen defects in high surface area oxide nanoparticles has been proposed as a potential recipe for weak ferromagnetism (Coey et al., New J. Phys. 12, 053025 (2010)).

Osteoarthritis, a major global cause of pain and disability, is driven by the irreversible degradation of hyaline cartilage in the joints. Cartilage tissue engineering presents a promising therapeutic avenue, but success hinges on replicating the native physiological environment to guide cellular behavior and generate tissue constructs that mimic natural cartilage. Although electrical stimulation has been shown to enhance chondrogenesis and extracellular matrix production in two-dimensional (2D) cultures, the mechanisms underlying these effects remain poorly understood, particularly in three-dimensional (3D) models. Here, we report that direct scaffold-coupled electrical stimulation applied to 3D graphene foam bioscaffolds significantly enhances the mechanical properties of the resulting graphene foam-cell constructs. Using custom 3D-printed electrical stimulus chambers, we applied biphasic square impulses (20, 40, 60 mVpp at 1 kHz) for 5 min daily over 7 days. Stimulation at 60 mVpp increased the steady-state energy dissipation and equilibrium modulus by approximately 65 and 25%, respectively, as compared with unstimulated controls. 60 mVpp stimulation also yielded the highest cell density among stimulated samples. In addition, our custom chambers facilitated full submersion of the hydrophobic graphene foam in media, leading to enhanced cell attachment and integration across the scaffold surface and within its hollow branches. To assess this cellular integration, we employed colocalized confocal fluorescence microscopy and X-ray microCT imaging enabled by colloidal gold nanoparticle and fluorophore staining, which allowed visualization of cell distribution within the opaque scaffold's internal structure. These findings highlight the potential of a direct scaffold-coupled electrical stimulus to modulate the mechanical properties of engineered tissues and offer insights into the emergent behavior of cells within conductive 3D bioscaffolds.