T 0206/13 - Sufficiency and preferred features

EPO T 206/13

For the decision, click here.

Key points

• The present decision shows how to rebut an objection that the claim is too broad under Article 84 EPC.
• The Board states that for sufficiency of disclosure, also the embodiments of dependent claims and of optional features in claims must be disclosed in an enabling way. 

Reasons for the Decision

[...]

3. Main request - Sufficiency of disclosure

3.1 The invention pertains to the field of surface-enhanced spectroscopy (SES), and more particularly to the field of SES-active composite nanoparticles, and claim 1 is directed to a particle comprising a SES-active analyte bound to a metal nanoparticle, both the analyte and the nanoparticle being surrounded by an encapsulant. In addition, according to dependent claim 11 the encapsulant "comprises a polymer, preferably a polymer that does not interfere with the SERS activity".

In its decision the examining division held that a particle as defined in claim 1 with an encapsulant comprising a polymer as defined in dependent claim 11, and more particularly [preferably] with a polymer that does not interfere with the surface-enhanced Raman spectroscopy activity, was not sufficiently disclosed within the meaning of Article 83 EPC.

3.2 With the statement setting out the grounds of appeal the appellant submitted that, due to the expression "preferably" in the formulation of dependent claim 11, the preferred feature constituted only an illustrative and non-limiting feature and therefore an optional feature that does not restrict the claimed subject-matter. According to the appellant's contention, the preferred feature would not be relevant for the assessment of sufficiency of disclosure.

The Board, however, cannot accept the appellant's submissions to the effect that preferred or optional features defined in a claim should be disregarded in the assessment under Article 83 EPC. According to the established case law the requirement of sufficiency of disclosure defined in Article 83 EPC is only complied with if the disclosure of the invention allows the skilled person to perform, without undue burden, essentially all the embodiments covered by the claimed invention (see "Case law of the Boards of Appeal", EPO, 7th ed., 2013, Chapter II, section C-4.4). This applies in particular to the specific particular embodiments of an invention defined in dependent claims pursuant to Rule 43(3) EPC (see for instance decision T 1011/01, point 2.3 of the reasons) and, by the same token, to any optional feature defined in a claim since such a feature also constitutes, by its very nature, a particular embodiment of the claimed invention, irrespective of whether the optional feature is qualified as being "preferred" or not.

3.3 The main aspect raised by the examining division as regards the issue of sufficiency of disclosure of the invention defined in claims 1 and 11 is that the skilled person would have to perform a sequence of three steps in order to carry out the invention defined in dependent claim 11, namely

i) the selection of the appropriate polymer,

ii) the selection of the appropriate solvent for the polymer, and

iii) the selection of the appropriate thickness of the polymer encapsulant.

The Board, however, is not convinced by the examining division's reasoning that the skilled person would not have been able to implement the claimed invention, and in particular to implement the sequence of steps i) to iii) mentioned above.

3.3.1 First, it is noted that, as observed by the examining division in its decision, the disclosure of the application focuses mainly on encapsulants made of glass and that the description does not contain any specific example of the manufacture of the claimed particles with an encapsulant made of polymer. This finding alone, however, does not amount to an insufficient disclosure of the claimed invention as long as the skilled person would be able, without undue burden and without the exercise of inventive step, to manufacture the claimed particles with a polymer encapsulant, following, for instance, the three steps i) to iii) mentioned by the examining division, on the basis of the common general knowledge in this art.

3.3.2 As regards step i), the invention defined in dependent claim 11 requires that the encapsulant of the particle comprises a polymer, and according to a preferred feature of the claim the polymer does not interfere with the SERS activity. The skilled person would understand that the latter feature constitutes, by its very nature, not the formulation of a result to be achieved, but a selection rule to the effect that, when putting into practice the preferred feature, the polymer for the encapsulant should be selected among those polymers that do not interfere with the SERS activity involved in the claimed particles. Therefore, starting with a predetermined metal nanoparticle and a predetermined SES-active analyte having the characteristics defined in claim 1, the skilled person would select among the available polymers a polymer adapted to encapsulate the claimed particle and, optionally, satisfying the functional condition defined in dependent claim 11, i.e. a polymer that does not interfere with the SERS activity. As mentioned by the appellant and undisputed by the examining division, at the priority date of the application the skilled person had at his disposal standard reference books in the field of Raman spectroscopy with information on the SERS characteristics of polymers. In particular, the appellant has referred during the proceedings to the "Handbook of Fourier transform Raman and infrared spectra of polymers", A. H. Kuptsov et al., Elsevier, 1998, in which the spectral characteristics, including the Raman spectrum, of hundreds of common polymers are listed in detail. In view of this information readily available to the skilled person working in this field, the Board is of the opinion that, depending on the excitation wavelength and the range of wavelengths of operation determined by the SES-active analyte, the skilled person would have had no difficulty in selecting a polymer suitable for the manufacture of a particle as defined in dependent claim 11, i.e. suitable for encapsulating a metal nanoparticle and a SES-active analyte as defined in claim 1, and preferably without detriment of the SERS activity of the particle as formulated in the optional feature defined in dependent claim 11.

Therefore, the Board cannot follow the examining division's view that finding and selecting suitable polymers satisfying the functional definition given in dependent claim 11 would constitute an undue burden for the skilled person or would require carrying out an extensive research program.

3.3.3 As regards the solvent to be selected according to step ii) referred to above, the Board shares the appellant's opinion that it pertains to the common general knowledge of the skilled person to select the appropriate solvent according to the characteristics of the polymer.

The Board concurs with the examining division that the skilled person confronted with the problem of forming an encapsulant as claimed with a polymer selected as specified in point 3.3.2 above would have to adjust the experimental conditions to ensure the formation of the polymer encapsulant covering the particles, but there is no technical argument or evidence that this task would involve more than routine experimentation or would amount to an undue burden for the skilled person. On the contrary, the appellant submitted during the first-instance proceedings the results of two experimental tests (documents A1 and A2) in which particles as defined in claim 1 were manufactured with an encapsulant made of a polymer, and the experimental conditions used in these tests do not appear to go beyond the conventional conditions that the person skilled in this field would have considered on the basis of his general knowledge. The examining division objected that the experimental tests reported in documents A1 and A2 involve a polymer and a solvent having specific characteristics, but the Board cannot follow this objection because an experimental test requires, by its very nature, the use of specific materials and, in addition, the characteristics of the specific materials used in the experimental tests (an anionic polymer in a water solvent system, and a polystyrene with an organic solvent (MeCN) and a radical initiator (AIBN)) do not allow the conclusion that the selection of the materials would require technical considerations going beyond the common technical practice in this field.

3.3.4 As regards step iii) relating to the selection of the thickness of the polymer encapsulant, in its decision the examining division held that the features defined in dependent claim 11 relating to the encapsulant being composed of a polymer not interfering with the SERS activity would not allow the skilled person to select and adjust the appropriate thickness of the polymer.

However, as submitted by the appellant, sufficiency of disclosure within the meaning of Article 83 EPC is to be assessed on the basis of the application as a whole. The application already indicates values of the thickness of the encapsulant between 1 and 40 nm, and preferably between 3 and 10 nm (see present dependent claim 5), and this disclosure constitutes an explicit guidance as to the suitable values of the thickness of the encapsulant. In addition, the description of the application teaches in respect of the encapsulant that "coatings that are too thick - on the order of 1 micron or more - might preclude obtaining intense Raman spectra. Coatings too thin might lead to interference in the Raman spectrum of the analyte by the molecules on the encapsulant surface" (page 8, fourth paragraph); although this teaching is disclosed in the context of encapsulants made of glass (page 8, third and fifth paragraphs) and not of a polymer as required in dependent claim 11, the skilled person would understand that similar considerations apply to polymer encapsulants. The experimental tests submitted by the appellant during the first-instance proceedings (documents A1 and A2) and based on particles as claimed having a coating of a polymer encapsulating the particles show that working within the range of thicknesses disclosed in the application leads to encapsulated particles without essentially altering the SERS activity of the particles.

In these circumstances, the Board is satisfied that the aforementioned teaching in the description provides sufficient technical guidance enabling the skilled person to select the appropriate thickness of the polymer encapsulant so that the features required by dependent claim 11 are achieved. If necessary, SERS measurements would be sufficient to find an appropriate value of the thickness of the encapsulant, and the corresponding encapsulant having the appropriate value of the thickness can be manufactured by adjusting the experimental conditions.

3.3.5 It also follows from the above analysis that the amount of experimentation required for carrying out each of steps i) to iii) was not unduly burdensome and that consequently, contrary to the examining division's opinion, the sequence of these three steps would not have required the exercise of inventive step or an amount of experimentation that would have gone up exponentially with each step.

3.3.6 It is finally noted that, as submitted by the appellant, it was already known in the prior art, and more specifically in the field of SERS, to encapsulate nanometre-sized metal particles with a polymer, as shown in document B1 (title, abstract, section "Introduction", and "Scheme 1" on page 7981) and in document B2 (title, abstract and section "Introduction"), these two documents disclosing and discussing different techniques for the formation of polymer-protected metal and bimetallic colloids for use in SERS. In the Board's view, the fact that in the present case the polymer encapsulates not only a metal particle but a metal particle having bond to it a SES-active analyte does not fundamentally change the encapsulating technique of metal nanoparticles disclosed in these documents. Thus, documents B1 and B2 constitute evidence that is at variance with the examining division's contention that the skilled person would be confronted with significant difficulties or would have to exercise inventive skills when trying to encapsulate with a polymer a metal nanoparticle having bound to it a SES-active analyte in order to carry out the claimed invention.

3.4 In its decision the examining division, in the context of the assessment of sufficiency of disclosure of claims 1 and 11, also referred to other technical aspects which, in its opinion, were not sufficiently disclosed within the meaning of Article 83 EPC. In particular, the examining division held that there is no guidance in the application as to which polymers "solve the objective technical problem" and as to how to select the appropriate polymers since they need to be "easily derivatizable [sic] to be of any use".

These technical aspects, however, are not defined in claims 1 and 11 and consequently, as submitted by the appellant, they are not to be considered in the assessment under Article 83 EPC of the invention defined in claims 1 and 11. Indeed, the requirement of sufficiency of disclosure set forth in Article 83 EPC relates to the invention defined in the claims, and in particular to the combination of structural and functional features of the claimed invention, and there is no legal basis for extending such a requirement to also encompass other technical aspects possibly associated with the invention (in particular, technical features or effects mentioned in the description) but not required by the claimed subject-matter. Thus, such technical aspects might be pertinent in the assessment of other requirements of the EPC (in particular, the requirements of Article 84 and 56 EPC, see for instance decision T 2001/12, point 4.4 of the reasons), but the question of whether the disclosure of the application would enable the skilled person to achieve such non-claimed technical aspects cannot legitimately be raised under Article 83 EPC (see decision T 2001/12, supra, point 3.4 of the reasons).

3.5 The examining division also expressed in an obiter dictum of the decision its view that there is no evidence in the application that all the metals listed in claim 1, i.e. Au, Ag, Cu, Na, Al and Cr, are suitable for SERS.

Although the examining division raised this issue under Article 84 EPC, the Board understands the objection as rather pertaining to the requirements of Article 83 EPC. In any case, the examples of the application (see Fig. 4 to 8 and the corresponding description) and also the experimental tests (documents A1 and A2) submitted by the appellant and considered in points 3.3.3 and 3.3.4 above show that Au and Ag are suitable for SERS. In addition, the documents of the state of the art considered during the first-instance proceedings constitute further supporting evidence that nanoparticles of the metals specified in claim 1 are appropriate for use in SERS. In particular, document D1 discloses the use of gold and silver colloids as metal nanoparticles in SERS (title, page 4903, second column, second paragraph, and Fig. 1 to 3), and document D6 discloses that "with visible-wavelength excitation, the SERS phenomenon occurs most efficiently on surfaces of precious metals (Ag, Au, Cu) [...]. Certain transition metals that have been shown to be SERS-active include Pt and Ni [...]. Other materials, such as [...] Na, [...] and Al, have also been investigated for SERS." (page 561, first column, second paragraph). As regards the last of the metals listed in claim 1, i.e. the transition metal Cr, the Board considers that in view of the aforementioned disclosures relating to the specific use in SERS of Au, Ag, Cu, Na and Al and to the general use of further transition metals, and in the absence of any specific technical argument or evidence in support of the examining division's view, there is no basis for rendering plausible, let alone conclusive, that the invention defined in claim 1 cannot be carried out on the basis of the transition metal Cr playing the role of the SERS-active metal.

3.6 It follows from the above considerations and conclusions that the Board does not find persuasive the examining division's view that the claimed invention is not sufficiently disclosed within the meaning of Article 83 EPC.