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Insights Into the Structure of Sunscreen Lotion: A Small-Angle Neutron Scattering Study


In the paper attention has been given to sunscreen lotions their components and mode of operation on the body. Several studies through various authors have done to disentangle the interior structure of ointments and lotions. Initially, to understand this internal oil structure in water creams (o/w creams). Differential calorimeter, x-ray deflection with transmission electron microscopy techniques were used to unravel some of the internal structures of the lotions. The internal structure was revealed to be composed of five domains (Sopyan, et al 2018). While related researches have been done unraveling the components of creams, the paper focuses on understanding the effect and impact of these constituents to the mode of action of these preservatives and UV filters present therein. The paper uses the Small-Angle Neutron Scattering (SANS) methodology.

The Small-Angle Neutron Scattering Study attempts to address some of the complexities of this formulation by using standard prepared oil-water lotion with various preservatives to access the impact and extend of each preservative. While its known that lotions have different concentrations and types of preservatives, moisturizers and Ultra Violet Filters, the study research conducted for the report involved use of various concentrations and different types to cater for this disparity. In the lotions used in the report, the chemical compositions included the presence or nonappearance of pentane diol ((1, 5-PD), hexane diol (1, 2-HD), with an array of UV 4 filters in D2O. This was followed by carrying out the SANS at 25ᵒC followed by an exploration of Q-scale on ZOOM amid 0.0024 to0.5 Å-1. After containing the samples in one millimeter path interval, Ultra Violet- spectrophotometer grade. They equilibrated after almost 5 minutes and then transferred to the beamline. The clarity with which the procedures were carried out exhibits precision of the highest order.

Scattering data is normalized for sample transmission and distribution of wavelength while the quartz cells are filled with D2O and adjusted for linearity and efficacy in detection using specific software package. By means of a model that accounts for the manifestation of ellipsoidal oil droplets, lamellar phase on the SAS view the data from the lotions is filtered using the fluorescent in situ hybridization (FISH) which accounts for every oil drop ellipsoidal globule. The surfactant captured layers are captured in terms of thickness, separation, and Gaussian distribution. This shows the precision and the reliability of the SANS through which the procedures were carried out especially when the models were treated as Para crystals( M, L, D, and Gaussian distribution) to capture every facet of the crystal that passes through the sight. The results are reliably and correctly reported.

Grounded on evaluating this manuscript, I will be deliberating the strength and weaknesses of the report trailed by the originality of the review article and lastly my recommendation,

The Strengths and Weaknesses of the Manuscript

Small-Angle Neutron Scattering manuscript addresses some of the complexities of this formulation by using standard prepared oil-water lotion with various preservatives to access the impact and extend of each preservative. The UV filters and other preservatives comes with other effects on the body of the users. Through differential scanning and X-ray diffraction, it was observed that the microstructures are modeled into five domains comprising of the surfactants, water, and oil phase bilayers as consistency enhancers. Although no full scientific information is available to fully substantiate how this array of elements successfully shield the body from the harmful effects of the sun.

The SANS prepared from lotions without any additives (L1) or filter. In figure 1, the leading features observed: a stout scattering strength at little Q value for great oil drops succeeding an approximately -3.5 Q value dependence signifying the globular shape of the drops. At the peak Q value of approximately 0.14 A-1 which matches a D- space value of 42A. This recommends the possibility of lamellar structure rather than surfactants on the upper part of the oil drop. Moreover, the literature explored in the same field verified by data fitting for an oil drop of equatorial radius of 1500A, polar radius of 300A with a coexisting one bilayer thickness of 52A supports the findings from the report. However, the theoretical 42A value neither captures the precise peak location in the SANS outline nor capturing general structures showed at low Q values implying that the bilayer is insensitive to other aspects like the existence of oil, size polydispersity etc.

In working out the SANS from lotions with preservatives, they considered using 1,5 pentane diol and 1,2 hexane diol which literally has a profound influence on the internal structure of the lotion. Having prepared lotions with a water to water percentage ratio of 2.5 in figure 2. The change is surprising and unexpected as no partitions in to hydrophobic phases is seen due to water solubility. The presence of Bragg peaks brings a new concept and knowledge in the field since initially creams with Q values approximately between 0.012 and 0.024A that corresponded to D- spacing standards of 525 and 260A. Clear correlation exists between lotions prepared with a 2.5 water to water percentage ratio incorporated with 1, 2 HD, L3 where Q values approximately at 0.011.and 0.022A-1 and the results obtained previously for creams formulated with a 10 percentage water to water ratio, (Ahmadi et al)

In sub-topic 3.3 they have discussed the response of SANS with organic UV filters. From figure 3 a differential comparison has been done against variables highlighted earlier. The weaker peak shapes composed of 1, 5 PD and 1, 2 HD points to the existence of a further interrupted structure with a lower capacity fraction. Taking in to consideration the coefficient value for EMC, it’s assumed that an increase in affinity to oil and not the hydrophobic chains present in the structure. Nonetheless, the disruption of lamellar bodies most likely implies solubilization within the hydrophobic chains. Which was confirmed by data modelling in Table 3. This demonstrates a good data analysis and the method used. The data fit in the multilayer model used with other systems weren’t successful but the data from SANS was a success since clear globular shape were observed.

In the SANS with preservatives and organic UV filters. A realistic approach in the study was employed by imitating the composite composition of the lotions accessible to consumers looking for sun protection. SANS profile components featured a resilient Q-4 dependence through introduction of preservatives to the system. Figure 4 data shows the results obtained indicating a bigger spacing between layers. This is steady with reports of the data model from Table 4 with positioning standards approximately between 425 – 400A for creams prepared with filters and respective preservatives. This advocates the presence of all the groups under scrutiny hence validating the aim of the research.

The changes seen from the SANS statistics from the lotions primed with the four filters shows an overall scattering profile from the systems. It also depicts the association of diols with lamellar networks within the prepared lotions. The behavior could be attributes to the interaction exerted by the two diols. It’s reported that surface interactions of 1, 5 –PD with active components at similar concentrations depicts the same results. (Selwyn & Renaud-Assemat, 2020). This supports the initial hypothesis of the manuscript that this preservatives and organic filters included therein have impact on the microstructure on the lotions.

Small-Angle Neutron Scattering (SANS) technique captures the multilayers of M surfactant, L of thickness, separation D, and the Gaussian distribution. The stated values of L heterogeneity together shows that they have an insignificant influence on the general quality within sensible boundaries as the report states. This invalidates the necessity considering the thickness of the microstructures when UV filters and other preservatives were included in the cream compositions. Surface granularity for Tables 3, 4, and 5 of different multilayers for various preservatives used before scattering can be determined from line profile through a segment of a surface (Equation 1)

𝑆𝑎 = 𝐿 ∫L0|(𝑥)|𝑑𝑥

Equation 1: Calculation of mean surface granularity

Where is the estimated size, is the tallness and is the distance laterally

Measuring Sa equates to the area between the coarseness shape and its mean line (Equation 1). If the Sa values are high, then the pores on the sample will be wide. The pores present capture nanoparticles inside hence increasing the surface area where the particles can be adsorbed. Using this formula could have countered the invalidity brought about by the L thickness and D separation in the procedures used.


Constraining the bilayer thickness to theoretical 42Ⱥ doesn’t capture the SANS profile. The general structures observed at low to mid Q are also not captured. This shows that the bilayer is subtle to other factors such like polydispersity, volume, and the manifestation of oil. According to Selwyn, and Renaud-Assemat (2020). Correlating surface granularity with that of superficial charge it’s distinct that the Sa shows a higher adsorption rate than those creams in which no UV filters or preservatives are present. This shows why neglecting the incorporation of formula 1 above discredits the data analysis.

SANS from lotions with preservatives like 1, 5 pentane diol (1,5-PD) together with 1, 2 hexane diol(1,2HD) has a weighty impact on the internal structure of the lotion with significant variations in the profiles observed. On the other hand, lotions comprising of a range of preservatives like 1,5 pentane diol,1,2 hexane diol with UV filters ( EMCAVB,EHT, and BMT) at 7.0,2.0,2.0 and 5.0 water to water percentage ratio respectively and their mixtures (Ahmadi The SANS results obtained from a 2.5 water to water percentage ratio for 1,5 PD(L2) shows the availability of definite lamellar structure through the Bragg peaks which were weaker than conventionally experiential lotions with Q values approximately equivalent to 0.012 to 0.024A-1. Matching to d-spacing values of approximately equal to 520 and 260 Ǻ. To add relevance to the research the standard 5.0 w/w % needs to be used instead of the 2.5 w/w% used for the preservatives and UV filters.

Creams formulated with 10w/w % surfactant (SDS) concentrations show distinct Bragg peaks in contrast to those well-defined at 2.5w/w % and 4w/w % surfactant molarity (Barbosa, et al., 2019). Data fitting to multilayer Table 2 reveals two structurally similar bilayers present in the SANS. This is expected to show an advanced surfactant concentration which introduces phase transition as lamellar structures in cream could be substituted by other structures. However, this was not the case with the study as the interaction encouraged the manifestation and development of lamellar structures within the lotion structures. (Ah Hamad et al.).

The decreased arrangement value (30 Ǻ) in the cream equipped with 1, 2-HD is further significant than lamellae breadth, and that the existence of 1, 2-HD has further suggests on the interlamellarlly water which permits additional research. Constraining the d-spacing value from the SANS data fitting value routine is hence incapable to replicate the results. This again calls for revision on a suitable method to be used to address this. Complex interactions of preservatives with internal structures of lotions can further indicate the differences seen between the D spacing and the fitting routine of the D values, for the creams manufactured with 1,5PD and 1,2-HD in that order.

The report states that data fitting by means of the multilayer model for BMT, L7 incorporated with other systems was not fruitful while those ones prepared the structure fits very fine to the ellipsoidal and lamellar prototype used for the blank creams. These gives insufficient credit to other authors who have contributed to the field. Interestingly, SANS statistics of the prepared ointments with UV filters together with the diols associate with lamellar network present inside the creams with high concentrations of water to water percentage ratio of sixteen.(16w/w %). (Isnin, Mustapha, & Othman,. (2018).

The novelty of the research

The piece being an appraisal article, I considered the new findings in terms of facts other than outcomes found in this manuscript. In my honest submission, the revisions established before have given lots of insights in to the structure of sunscreen lotions. The SANS figures presented a strong reliance on Q which diversed from Q-3.5 to Q-4 this indicates a change in the oil drop figure from ellipsoidal to globular. A sequence of peaks at mid and low Q values depicted the existence of various additives as lotions devoid of additives indicated presence of ellipsoidal oil drops.


My commendation as a critic would be to consent the paper with minor revisions. The negligible revisions would be required in the flaws that I have heighted above. Relevant supporting literature information should be found for the type of emulsifiers used in the preparation of ointments and balms containing these diols and their impact on antimicrobial efficacy.

The author may also find suitable techniques on how to improve the reproducibility of results and also those that would help to entirely explain the major decline in the positioning of D values amongst the bilayers in the ointments primed using UV filters and the diols.

Since data fitting is by means of multilayer model in correspondence with systems with present additives, the author needs to consider employing techniques that could help address this menace. Furthermore, Correlating surface granularity with that of superficial charge it’s distinct that the Sa shows a higher adsorption rate than those creams in which no UV filters or preservatives are present. Hence the need to review the SANS technique manuscript ounce more before publishing.


Following the insufficient credit given to the authors of the literature supported herein, the inability to reproduce similar results when similar concentrations of UV filters and preservatives were used in the study. I, therefore, find it necessary to recommend a review of the paper before it’s submitted for publishing. Despite the report being clear and detailed about the Small-angle neutron scattering (SANS), the report gives fewer insights to literature and other similar research is done, evident when a comparison is given in cases where UV filters and other preservatives are used for Tables 2, 3 and 4. The report gives unsatisfactory analysis since it calls for further investigations to fully decide if the brand of emulsifier included in formulating creams and ointments that have diols affects antimicrobial efficiency. I therefore highly accept the publishing of the report after the minor revision highlighted herein are addressed.


Barbosa, J. S., Neto, D. M. A., Freire, R. M., Rocha, J. S., Fechine, L. M. U. D., Denardin, J. C., … & Fechine, P. B. A. (2018). Ultrafast sonochemistry-based approach to coat TiO2 commercial particles for sunscreen formulation. Ultrasonics sonochemistry, 48, 340-348.

Barbosa, J. S., Neto, D. M. A., Freire, R. M., Rocha, J. S., Fechine, L. M. U. D., Denardin, J. C., … & Fechine, P. B. A. (2018). Ultrafast sonochemistry-based approach to coat TiO2 commercial particles for sunscreen formulation. Ultrasonics sonochemistry, 48, 340-348.

Geoffrey, K., Mwangi, A. N., & Maru, S. M. (2019). Sunscreen products: Rationale for use, formulation development, and regulatory considerations. Saudi Pharmaceutical Journal, 27(7), 1009-1018.

Isnin, S. F., Mustapha, R., & Othman, W. M. (2018). Engineering students’ perspectives on the need for a new module in technical report writing at Polytechnic in Malaysia. Journal of Engineering Science and Technology (JESTEC), 31-38.

Selwyn, R., & Renaud-Assemat, I. (2020). Developing technical report writing skills in first and second-year engineering students: a case study using self-reflection. Higher Education Pedagogies, 5(1), 19-29.


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