Hydrogels are three-dimensional polymeric systems, being able to accommodate different categories of bioactive agents and act as promising drug delivery systems in many different biomedical applications. Due to their extended 3D network, hydrogels exhibit many advantages, such as extensive loading capacity and controlled drug release profiles, combined with characteristics such as biocompatibility and biodegradability, due to their constructive polymeric biomaterials. Moreover, hydrogels are capable of being administered via different routes of administration, including systemic and topical ones, due to their tunable characteristics. Stimuli-responsive hydrogels are characterized as smart biomaterials, while environmental stimuli, such as pH, can be employed to trigger on-demand drug release from the hydrogels via the provocation of conformational changes. In the present study, an emphasis on the pH-responsive hydrogels is taking place through various literature cases in drug delivery, wound healing, and some alternative applications, including implantation, oral administration, etc., wherein many different polymeric derivatives have been utilized. Moreover, the role of each used polymer or polymeric combination with other functional biomaterials, their mode of structure formation (for example, crosslinking), and their content release mechanism are highlighted, as well as the therapeutic effect of the hydrogels on different pathological conditions, as promising candidates for pharmaceutical applications.

Lipid-based nanocarriers are ideal drug delivery systems for transdermal administration due to their biocompatibility and biodegradability. Their lipophilicity and/or similarity to the natural lipids of the epidermis enable intermolecular interactions with the lipid membrane and therefore result in effective passage through the skin. The purpose of this review is to focus on lipid-based drug delivery nanoplatforms administered via the transdermal route by summarizing the most recent developments with the intention of fast clinical translation. Liposomes, solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), ethosomes, and transfersomes exhibit ideal physicochemical characteristics and encapsulation efficiency to enhance the effectiveness of the incorporated Active Pharmaceutical Ingredients (APIs). The state of the art for fabricating transcutaneous lipid drug delivery nanoparticles and the strategies for overcoming the current obstacles, as well as the added value of novel formulations, will be discussed within the scope of Quality by Design applications. The limitations and challenges that still exist will also be considered.

Hybrid nanoparticles have gained a lot of attention due to their advantageous properties and versatility in pharmaceutical applications. In this perspective, the formation of novel systems and the exploration of their characteristics not only from a physicochemical but also from a biophysical perspective could promote the development of new nanoplatforms with well-defined features. In the current work, lipid/copolymer bilayers were formed in different lipid to copolymer ratios and examined via differential scanning calorimetry as a preformulation study to decipher the interactions between the biomaterials, followed by nanostructure preparation by the thin-film hydration method. Physicochemical and toxicological evaluations were conducted utilizing light scattering techniques, fluorescence spectroscopy, and MTS assay. 1,2-dioctadecanoyl-sn-glycero-3-phosphocholine (DSPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) in different weight ratios were the chosen lipids, while a linear random copolymer with pH- and thermoresponsive properties comprised of oligo (ethylene glycol) methyl ether methacrylate (OEGMA) and 2-(diisopropylamino) ethyl methacrylate (DIPAEMA) in different ratios was used. According to our results, non-toxic hybrid nanosystems with stimuli-responsive properties were successfully formulated, and the main parameters influencing their overall performance were the hydrophilic/hydrophobic balance, lipid to polymer ratio, and more importantly the random copolymer topology. Hopefully, this investigation can promote a better understanding of the factors affecting the behavior of hybrid systems.

Despite the appealing properties of random copolymers, the use of these biomaterials in association with phospholipids is still limited, as several aspects of their performance have not been investigated. The aim of this work is the formulation of lipid/random copolymer platforms and the comprehensive study of their features by multiple advanced characterization techniques. Both biomaterials are amphiphilic, including two phospholipids (1,2-dioctadecanoyl-sn-glycero-3-phosphocholine (DSPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)) and a statistical copolymer of oligo (ethylene glycol) methyl ether methacrylate (OEGMA) and 2-(diisopropylamino) ethyl methacrylate (DIPAEMA). We examined the design parameters, including the lipid composition, the % comonomer ratio, and the lipid-to-polymer ratio that could be critical for their behavior. The structures were also probed in different conditions. To the best of the authors’ knowledge, this is the first time that P(OEGMA-co-DIPAEMA)/lipid hybrid colloidal dispersions have been investigated from a membrane mechanics, biophysical, and morphological perspective. Among other parameters, the copolymer architecture and the hydrophilic to hydrophobic balance are deemed fundamental parameters for the biomaterial co-assembly, having an impact on the membrane’s fluidity, morphology, and thermodynamics. Exploiting their unique characteristics, the most promising candidates were utilized for methotrexate (MTX) loading to explore their encapsulation capability and potential antitumor efficacy in vitro in various cell lines.

Parenteral nutrition is an integral part of the nutritional support of critically ill neonates, infants, and children in the intensive care units (ICUs) and at home. Therefore, the adequacy and the effectiveness of parenteral nutrition, PN, support are among the major concerns of doctors and pharmacists. The aim of this study is the physicochemical and stability evaluation of nanoemulsions, which are used for parenteral nutrition. These nanoemulsions are for intravenous (IV) administration of lipids, amino acids, glucose, electrolytes, trace elements as well as vitamins. Light scattering techniques are used for the identification of the hydrodynamic diameter (D_h), size polydispersity index (PDI), and the ζ-potential of the prepared nanoemulsions. Stability assessment is performed in different conditions, mimicking those of the hospital. The stability studies involve shelf-life measurement of these NEs over 10 days in two storage conditions (25 °C and 4 °C) using dynamic light scattering. According to the US Pharmacopeia, the droplet size should be under the upper limit of 500 nm (0.5 μm). Transmission electron microscopy (TEM) is used for the shape of the droplets of the nanoemulsion emulsion for parenteral nutrition for the first time. The results showed that the droplet size was around 300 nm, with a homogeneous population and negative ζ-potential. The morphology was vesicular and spherical, typical for NE droplet shape. The results from all the characterization techniques show that the formulations meet the high-quality standards of nanoemulsions for neonates, infants and children.