In Situ Imaging of Subcutaneous Drug Delivery Systems Using Microspatially Offset Low-Frequency Raman Spectroscopy.

The noninvasive in situ monitoring of the status of drug retention and implant integrity of subcutaneous implants would allow optimization of therapy and avoid periods of subtherapeutic delivery kinetics. A proof-of principle study was conducted to determine the use of microspatially offset low-frequency Raman spectroscopy (micro-SOLFRS) for nonintrusive in situ analysis of subcutaneous drug delivery systems. Caffeine was used as the model drug, and it was embedded in a circular-shape Soluplus matrix via vacuum compression molding. For the exploratory analysis, prototype implants were positioned underneath skin tissue samples, and various caffeine concentrations (1-50% w/w) and micro-SOLFRS displacement settings (Δz = 0-8 mm) were tested from the pseudo three-dimensional (3D)-imaging perspective. This format allowed the optimization of real-time micro-SOLFRS analysis of implants through skin tissue that was embedded in an agarose hydrogel. Notably, this analytical approach allowed the temporal and spatial erosion of the implant and solid-state transformations of caffeine to be distinguished. The spectrometric results correlated with complementary high-performance liquid chromatography (HPLC) determination of changes in drug concentration, illustrating drug dissipation/diffusion characteristics. The discovered capability of micro-SOLFRS for in situ measurements of drugs and implants makes it attractive for biomedical diagnostics that, ultimately, could result in development of a new point-of-care technology.

In Operando Analysis of Milk-Based Oral Formulations during Digestion Using Synchrotron Small-Angle X-ray Scattering Coupled to Low-Frequency Raman Spectroscopy.

A low-frequency Raman (LFR) probe was coupled to an in-line small-angle X-ray scattering (SAXS) beamline to test the capabilities of a combinatory approach for the determination of lipid and drug behavior during the enzymatic lipolysis of milk-based oral formulations. Cinnarizine was used as the model drug, and its solubilization dynamics as well as its potential impact on the supramolecular structures formed by the digestion products of bovine milk were evaluated from the perspective of both techniques. The SAXS data were superior in distinguishing various liquid crystalline assemblies formed during the digestion process, with LFR providing complementary information regarding the formation of calcium soaps. On the other hand, studying changes in the LFR domain allowed the differentiation of drug solubilization and precipitation; processes that were less clear from the X-ray scattering data. Given the relative simplicity of the combined experimental setup, these results highlight the advantages that the combination of the two techniques can provide for understanding and developing new lipid-based formulations and will help to translate the results obtained at synchrotron facilities to routine analysis procedures in laboratory/industry-based environments.

The biomolecular gastrointestinal corona in oral drug delivery.

The formation of a biomolecular corona on exogenous particles in plasma is well studied and is known to dictate the biodistribution and cellular interactions of nanomedicine formulations. In contrast, while the oral route is the most favorable administration method for pharmaceuticals, little is known about the formation and composition of the corona formed by biomolecules on particles within the gastrointestinal tract. This work reviews the current literature understanding of (1) the formation of drug particles after oral administration, (2) the formation of a biomolecular corona within the gastrointestinal tract ("the gastrointestinal corona"), and (3) the possible implications of the formation of a gastrointestinal corona on the interactions of drug particles with their biological environment. In doing so, this work aims to establish the significance of the formation of a gastrointestinal corona in oral drug delivery to ultimately arrive at new avenues to control the behavior of orally administered pharmaceuticals.

The Influence of Gastrointestinal Biomolecules on Solid-State Transformations in Pharmaceutical Particulates.

Adsorption of gut relevant biomolecules onto particles after oral administration of solid oral dosage forms is expected to form a "gastrointestinal corona", which could influence solution-mediated solid-state transformations on exposure of drug particles to gastrointestinal fluids. Low-frequency Raman (LFR) spectroscopy was used in this study to investigate in situ solid-state phase transformations under biorelevant temperature and pH conditions along with the presence of biomolecules. Melt-quenched amorphous indomethacin was used as a model solid particulate, and its solid-state behavior was evaluated at 37 °C and pH 1.2-6.8 with or without the presence of typical bile salt/phospholipid mixtures emulating fed-state conditions. Overall, a change in the solid-state transformation pathway from amorphous to crystalline drug was observed, where an intermediate ε-form that initially formed at pH 6.8 was suppressed by the addition of endogenous gastrointestinal biomolecules. These solid-state changes were corroborated using time-resolved synchrotron small- and wide-angle X-ray scattering (SAXS/WAXS). Additionally, the bile salt and phospholipid mixture partly prevented the otherwise strong aggregation between drug particles at more acidic conditions (pH ≤ 4.5) and helped to shift the balance against the intrinsic hydrophobicity of indomethacin as well as the plasticization effect brought about by the physiological temperature (i.e., the stickiness arising from the supercooled liquid state at 37 °C). The overall results highlight the importance of evaluating the impact that endogenous biomolecules may have on the solid-state characteristics of drug molecules in dissolution media, where analytical tools such as LFR spectroscopy can serve as an attractive avenue for accessing time-resolved solid-state information on time-scales that are difficult to achieve with other techniques such as X-ray diffraction.

Elucidating the nanostructure of small interfering RNA-loaded lipidoid-polymer hybrid nanoparticles.

We analyzed the structural and material properties of small interfering RNA (siRNA)-loaded lipid-polymer hybrid nanoparticles (LPNs) containing ionizable lipidoid and poly(dl-lactic-co-glycolic acid) (PLGA) using small-angle X-ray scattering, cryogenic transmission electron microscopy, polarized light microscopy, the Langmuir monolayer methodology, differential scanning calorimetry, and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. Scattering analyses showed that bulk lipidoid self-assemble into lamellar structures with a d-spacing of 38 Å, whereas lipidoid-siRNA lipoplexes display an in-plane lateral organization of siRNA in between lipidoid bilayers with a repeat distance of approximately 55 Å. The siRNA-loaded LPNs adopted a core-shell structure with an interaxial alignment of siRNA between lipidoid shell bilayers. Langmuir monolayer experiments showed a distinct interaction between the lipidoid headgroups and siRNA, which was dependent on buffer subphase pH. Thermal analyses suggested that PLGA and lipidoid interact, which was evident from a shift in the phase transition temperature of lipidoid, and the thermotropic phase behavior of lipidoid was affected by inclusion of siRNA. ATR-FTIR data confirmed the shift or disappearance of characteristic absorption bands of siRNA after lipidoid binding. In conclusion, siRNA-loaded LPNs display a core-shell structure, wherein the polymeric core functions as a colloid matrix support for siRNA-loaded lipidoid shell layers.

Opportunities and Challenges in the Delivery of mRNA-based Vaccines.

In the past few years, there has been increasing focus on the use of messenger RNA (mRNA) as a new therapeutic modality. Current clinical efforts encompassing mRNA-based drugs are directed toward infectious disease vaccines, cancer immunotherapies, therapeutic protein replacement therapies, and treatment of genetic diseases. However, challenges that impede the successful translation of these molecules into drugs are that (i) mRNA is a very large molecule, (ii) it is intrinsically unstable and prone to degradation by nucleases, and (iii) it activates the immune system. Although some of these challenges have been partially solved by means of chemical modification of the mRNA, intracellular delivery of mRNA still represents a major hurdle. The clinical translation of mRNA-based therapeutics requires delivery technologies that can ensure stabilization of mRNA under physiological conditions. Here, we (i) review opportunities and challenges in the delivery of mRNA-based therapeutics with a focus on non-viral delivery systems, (ii) present the clinical status of mRNA vaccines, and (iii) highlight perspectives on the future of this promising new type of medicine.