Fractal analysis as a complementary approach to predict the stability of drug delivery nano systems in aqueous and biological media: A regulatory proposal or a dream?

Nanomedicines and Nanosimilars: Looking for a New and Dynamic Regulatory "Astrolabe" Inspired System

The application of the nanotechnology in medicine and pharmaceutics opens new horizons in therapeutics. Several nanomedicines are in the market and an increasing number is in clinical trials. But which is the advantage of the medicines in nanoscale? The scientists and the regulatory authorities agree that the size and consequently the physiochemical/biological properties of nanomaterials play a key role in their safety and effectiveness. Additionally, all of them agree that a new scientific-based regulatory landscape is required for the establishment of nanomedicines in the market. The aim of this review is to investigate the parameters that the scientists and the regulatory authorities should take into account in order to build up a dynamic regulatory landscape for nanomedicines. For this reason, we propose an "astrolabe-like system" as the guide for establishing the regulatory approval process. Its function is based on the different physicochemical/biological properties in comparison to low molecular weight drugs.

Benefits of Fractal Approaches in Solid Dosage Form Development

Pharmaceutical formulations are complex systems consisting of active pharmaceutical ingredient(s) and a number of excipients selected to provide the intended performance of the product. The understanding of materials' properties and technological processes is a requirement for building quality into pharmaceutical products. Such understanding is gained mostly from empirical correlations of material and process factors with quality attributes of the final product. However, it seems also important to gain knowledge based on mechanistic considerations. Promising is here to study morphological and/or topological characteristics of particles and their aggregates. These geometric aspects must be taken into account to better understand how product attributes emerge from raw materials, which includes, for example, mechanical tablet properties, disintegration or dissolution behavior. Regulatory agencies worldwide are promoting the use of physical models in pharmaceutics to design quality into a final product. This review deals with pharmaceutical applications of theoretical models, focusing on percolation theory, fractal, and multifractal geometry. The use of these so-called fractal approaches improves the understanding of different aspects in the development of solid dosage forms, for example by identifying critical drug and excipient concentrations, as well as to study effects of heterogeneity on dosage form performance. The aim is to link micro- and macrostructure to the emerging quality attributes of the pharmaceutical solid dosage forms as a strategy to enhance mechanistic understanding and to advance pharmaceutical development and manufacturing processes.

Early stages of drug crystallization from amorphous solid dispersion via fractal analysis based on chemical imaging

Early stages of crystallization from amorphous solid dispersion (ASD) are typically not detected by means of standard methods like powder X-ray diffraction (XRPD). The aim of this study is therefore to evaluate if fractal analysis based on energy dispersive X-ray imaging can provide the means to identify early signs of physical instability. ASDs of the poorly water-soluble compound, felodipine (FEL) were prepared by solvent evaporation using different grades of HPMCAS, at 50 wt% drug loading. Samples were stored at accelerated conditions of 40 °C. Scanning electron microscopy equipped with an energy-dispersive X-ray spectroscopy (SEM-EDS) was used for elemental mapping of tablet surfaces. Comparative data were generated with a standard XRPD and with more sensitive methods for detection of early instability, i.e. laser scanning confocal microscopy (LSM) and atomic force microscopy (AFM). The SEM-EDS identified changes of drug-rich domains that were confirmed by LSM and AFM. Early changes in drug clusters were also revealed by a multifractal analysis that indicated a beginning phase separation and drug crystallization. Therefore, the presented fractal cluster analysis based on chemical imaging bears much promise as a new method to detect early signs of physical instability in ASD, which is of great relevance for pharmaceutical development.

A multiscale mechanism of drug release from polymeric matrices: confirmation through a nonlinear theoretical model

In this paper, we propose a new approach for the dynamics of drug delivery systems, assimilated to complex systems, an approach based on concepts like fractality, non-differentiability, and multiscale evolution. The main advantage of using these concepts is the possibility of eliminating the approximations used in the standard approach by replacing complexity with fractality, that imposes, in mathematical terms, the mandatory use of the non-differential character of defined physical quantities. The theoretical model presented, validated for other physical systems, demonstrates its functionality also for drug delivery systems, highlighting, in addition, new insights into the complexity of this system. The spatio-temporal scales of system evolution are characterized through the fractality degree, as a measure of the complexity of the phenomena occurring at each scale. Numerical analysis of the experiment showed that the overall drug release kinetics can be obtained by composing "smaller release kinetics" occurring at scales appropriate for each phase of the drug release mechanism, phases whose expansion depends on the system density. Moreover, the uncertainties in establishing the exact limits of the phases were removed by applying the principle of scale superposition, resulting in a global fractality degree corresponding to the entire release kinetics. Even if the theoretical model is perfectible by identifying constants specific to each delivery system, this paper is intended to be the beginning of an alternative approach to drug delivery mechanisms.

Structural and thermal analysis of a hyper-branched exopolysaccharide produced by submerged fermentation of mushroom mycelium

An exopolysaccharide (PTR-EPS1) purified from the culture medium of the mycelial fermentation of Pleurotus tuber-regium had a weight-average molecular mass of 173.6 kDa and a radius of 55.6 nm.

Fractal geometry as a new approach for proving nanosimilarity: a reflection note

Nanosimilars are considered as new medicinal outcomes combining the generic drugs and the nanocarrier as an innovative excipient, in order to evaluate them as final products. They belong to the grey area - concerning the evaluation process - between generic drugs and biosimilar medicinal products. Generic drugs are well documented and a huge number of them are in market, replacing effectively the off-patent drugs. The scientific approach for releasing them to the market is based on bioequivalence studies, which are well documented and accepted by the regulatory agencies. On the other hand, the structural complexity of biological/biotechnology-derived products demands a new approach for the approval process taking into consideration that bioequivalence studies are not considered as sufficient as in generic drugs, and new clinical trials are needed to support their approval process of the product to the market. In proportion, due to technological complexity of nanomedicines, the approaches for proving the statistical identity or the similarity for generic and biosimilar products, respectively, with those of prototypes, are not considered as effective for nanosimilar products. The aim of this note is to propose a complementary approach which can provide realistic evidences concerning the nanosimilarity, based on fractal analysis. This approach is well fit with the structural complexity of nanomedicines and smooths the difficulties for proving the similarity between off-patent and nanosimilar products. Fractal analysis could be considered as the approach that completely characterizes the physicochemical/morphological characteristics of nanosimilar products and could be proposed as a start point for a deep discussion on nanosimilarity.